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v, K.W. Bldg

OCT 8 1964

Reference book not to be

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^ecknical ^iot& 247

SURVEY OF MAGNETIC THIN FILM MATERIALS

GEORGE W. REIMHERR

W5^V.,^S»« ¥1

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
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NATIONAL BUREAU OF STANDARDS

Technical Note 247

ISSUED SEPTEMBER 25, 1964

SURVEY OF MAGNETIC

THIN FILM MATERIALS

George W. Reimherr

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C., 20402 Price

A Survey of Magnetic Thin Film Materials

byGeorge William Reimherr

This survey lists the materials reportedly made

as a magnetic thin film, along with some of their

properties and potential applications . Research

activity using the less -frequently mentioned magnetic

film materials is noted. About 200 references are

cited.

1. Introduction

The growth of activity in magnetic thin film research is indicated

by the increasing number of papers published in this field. For

example, the Magnetic Materials Digest series zJ lists 26 papers in

1958, 33 in 1959, 70 in I960, 131 in 1961, and at least 180 papers in

1962 that concern magnetic thin films. Much of this activity, both for

research and for practical applications, has been with the nonmagnetostrictive 8lNi-19Fe permalloy composition. However, a sizable

activity has concerned other compositions, particularly as fabrication

techniques become better known.

This survey lists some of the properties, interesting features,

and proposed applications of the various magnetic film materials.

Research activity with theTesser -mentioned magnetic film materials is

included.

2. Structure and Magnetic Properties of Materials Reported

as a Magnetic Thin Film

The Key to Table I The following items represent the various column headings of

Table I, in the order of their appearance. All values (except Curie

temperature) are given for about 20° C.

1/

References (100) through (103).
1. Materials. These are the materials reportedly made in

the form of a magnetic thin film. In a few cases, the

source composition rather than the film composition is

given; these cases are noted by the words "source

composition. " - Magnetic films are prepared by a

variety of techniques, including vacuum evaporation,

electrodeposition, electroless deposition, and sputtering.

Substrates are generally of glass or of metal such as

aluminum, copper, gold, etc. , although such materials

as mica, MgO, NaCl, etc. , are also used.

2. Structure. The structure type is listed, along with the

lattice constants (a, c).

3. Curie temperature. Units are in degrees Celsius ( C).

4. Ms . This is the saturation magnetization, defined (in the

cgs-emu system) as B - H for very large H.

5. Hc. This is the coercive force reported for the material

as a magnetic thin film. Specific examples are sometimes

given in cases where a typical range of values is not readily

available

.

6. Hfc. This is the anisotropy field of the film. (See remarks

for Hc

, above. ) A few materials have no magnetic

anisotropy and are therefore listed as isotropic.

7. Ki. This is the crystalline anisotropy constant of the

material.

8. Xs« This represents the saturation magnetostriction of the

polycrystalline material.

9. References. The reference sources are listed in parentheses (1) ... (201). The selected bibliography appears at

the back.
1. oA

2. (b)

3. bcc

4. cc

5. (f)

6. fee

7. hep

8. hex

9. Hw

10. oe.

11. ref

12. temp

13. wt.

14. fisec.

15. r*-t

3. Other Abbreviations

y

Angstrom unit

value measured on. bulk material }J

body centered cubic

cubic centimeter

value measured on

film material f/

face centered cubic

hexagonal close packed

hexagonal

wall coercive force

oersteds

reference

temperature

weight

microseconds

about, approximately

U

In Table I, values given for the lattice constants, Curie

temperature, and Ms , were generally measured on the

bulk material; values for Ki and \s were measured on

bulk (b) or on film (f), while values of Hc and H^ were

measured on the film material. Values measured on the

bulk material for the lattice constants, Curie temperature,

Ms , K}, and X&, are generally considered applicable to the

thin film al^,o_3/ except possibly for the ultra-thin film

--- < ~ 30 A thick). However, values given for Hc and for

H^ are unique to the thin film, because of their strong

dependence on how the film is made.

Although this has not been verified in every case.
Table I. Structure and Magnetic Properties of Materials Reported

as a Magnetic Thin Film

Note to Accompany Table 1 To convert the given cgs-emu values to the International System (SI),

(1) Multiply the number of oersteds by 79- 58 ( = 1000/4tt) to

express H in amperes per meter, (2) Multiply the value of the

magnetization in gauss by 0. 001257 ( = 4ir 10 "^ to obtain the

magnetic polarization (intrinsic induction) in teslas.
Material Structure Curie Temp.

CO

Ms

(gauss) (oe.)

Hk

(oe.)

Kl(ergs/cc)

*s

laIron - bee bee

a = 2.861 A

(1)

(2)

770

(1)

(3)

1714

(1)

(3)

values

from

~10 (4) up to several

hundred

(5) see comments

also

+4.5xl05

(f) (6) +4.6xl0

5

(b) (3) +4.9+0.1xl05

(f) (4)

-7xl0"

6

(7)

(8)

lb Iron - fee fee

o a = 3.588 A

at room

temp. (9)

Neel

temp.

uncertain;

see comments

see comments

2aNickel

(fee)

fee a = 3.517 A

(2)

o a = 3.524 A

(10)

358

(1)

(3)

484.1

(1)

(3)

10 to 35 (ID

another

ref: (12),

Fig. 6

example:

4 to 12

(13)

-3.6xl04

to -4.5xl04

(f) (6) . -4.6xl0

4

(f) (14)

-5.5xl0

4

(b) (15)

-34xl0"

6

(7)

(8) (16)

2bNickel

(hep)

hep

a = 2.66 A

c = 4.29 A

(2)

see comments

3aCobalt

(hep)

hep

a = 2.514 A

c = 4.105 A

(2)

phase

change

occurs below

Curie

temp.

1422

(3) examples

:

35 (17)

40 (18)

5.3xl0

6

(b) (3) general

ref. for

bulk:

(19)

-70xlO"

6

(b) (3) ref. for polycrys.

cobalt:

(20)

3bCobalt

(fee) .

fee

a = 3.554 A

(2) a = 3.56±

0.01 A

(21)

1130

(1) 1131

(3)

(-1420) ref. for

bulk: (19) ref. for

films: see comments

see comments

ref. for

temp,

above

500° C:

(19)
Material Structure Curie Temp. Ms Hc Hk Kl ^s

(°C) (gauss) (oe.) (oe.) (ergs/cc)

4 Gadolinium hep 16 ref. (25) some

a = 3.622 A

c = 5.748 A

(22)

(1) (3) 17

(23)

(24)

(paramagnetic at room tern] >.)

(b) mention

in ref.

(26)

5 MnBi hex. 360 620 high, _-__ 9.1xl06 800xl0~6

o a = 4.287 A

(3) (3) probably (27) (27)

(27) several

c = 6.126 A thousand; other other

(27) see sec- tion on magnetic

thin film

papers

.

ref.:

(28) ref.:

(28)

6a81Ni-19Fe fee <~585 ~ 800 0.5 to 5.0; 2.5 to -1.6xl03 nearly

a = 3.54 A

(1) (1) typically 5.0; (f) (6) nonmag-

(1) 0.5Hk

to typically neto- 0.9Hk ~3. stric-

(29) (29) tive

alloy

(b) ; (f

)

(29)

6b50Ni-50Fe fee — 500 — 1270 example

:

.... 33xl0"3 r^26xl0

-6

o a~3.58 A

(3) (1) ~10 to 20 (b) (1) (30)

(1)

(3) for 45%

(30) permalloy

films

(18)

6c3Ni-97Fe bee ~770 ~1735 14.5 to 16 magneti- should

o a~2.862 A

(1) (32) cally be near

(1) 15 (rod)

(33)

9 (waffleiron)

(31)

isotropic

alloy

(31)

(32)

zero

7 Ni-Fe-Al ref.; (1),

p 386 for

the phase

diagram.

see section

film papers on thin
Material Structure Curie Temp. Ms Hc Hk Kl ^s

(°C) (gauss) (oe.) (oe.) (ergs/cc)

8a80Ni-17Fe- fee ^590 ~-835 3.9 6.0 nonmag3Co (1) (1) U) (29) (29) netostric-

(source 5.0 5.5 tive

composi- (34) (34) film

tion) 2.5 to 3.0

oe. are possible

(35)

(29)

8b57Ni-13Fe- fee ^760 ~1000 see 30 nonmag30Co (1) (1) (1) ref.

(36)

(36) netostric-

(source tive composi- film tion)

(36)

8c48.6M- fee — 830 ^1000 10 30 .— zero 2.8Fe- (1) (1) (1) (H„) (37) magneto48.6Co ~1030 (37) elastic

(source

composition)

(37)

sensitivity

(37)

8d45Ni-30Fe- fee ~720 -1260 example: example: believed 12xl0

-6 25Co

(1)

(1) (1) 6.9 to 38-42 to be (b) (1) (perminvar)

(approx.

715

(3) 1230(3)

7.5

(38)

(38) small -

(1) p 571 source composition)

9 Ni-Fe-Cr fee ref.: ref.: ~1 ~1 to 6 ____

(1) (1), (1) (H„) (39) (39)

(39) p 149 p 150

10Ni-Fe-Cu ref.:

(1), ref.:(1)

ref. :(1) p 154 p 155 p 156

>
Material Structure Curie Temp. MllS Hc H k Kl ^s

(°C) (gauss) (oe.) (oe.) (ergs/cc)

11 Ni-Fe-Mo fee ref.: (1) ref.: 0.7 (17) 2.2 to 50 nearly nearly

(some

specific

examples

noted)

(1) p 135 example

460°C for 4-79

permalloy

(3)

(1),

p 136 example:

~690 Ga for 4-79

permallo

(3

0.6 to 4.3

(40)

uss

y

)

(40)

~1.0 for

2% Mopermalloy

(29)

zero for

4-79 Mo- permalloy

(29)

nonmagnetostrictive

for 4-79

Mo-permalloy

(29)

12Ni-Fe-P 0.1 to 1.4

(41)

see section

film papers

0.9 to 1.4

(41)

on thin

films are gen- erally nonmagnetostrictive

(41)

13Fe-Al (22 bec ref.: (3), r-^950 ref. : to 25 atomic %

a~2.89-A p 5-172;

(43), p 837;

(1)

(b) (43)

Al) (1) (42)

(44)

14a50Fe-50Co bee 980 -1950 .... .... -70xl0

-3 67xl0"

6 (source

composi- a-2.85 A (3)

(3) (3) (1)

tion)

14b5Fe-95Co ~1090 ~1460 high values (small)

(1) (1) coer- about 10 ref.: civity times (1),

(29) that of 81Ni-19Fe

films

(29)

Fig. 13-

92

15Ni-Cu fee ref.

ref.: ref.:

(f) (45) (1), (1), (1),

p 308- p 310; P 573; ref.: (1), 310 (46) (3),

p 309 also

(46)

p 5-190
Material Structure Curie Temp. "s He «k Kl ^s

(°C) (gauss) (oe.) (oe.) (ergs/cc)

16Ni-Pd fee

(f) (45)

ref.:

(3),

p 5-173

ref.:

(b) (47)

17Ni-alloys see section on

(other)

thin film papers

18Co-Cu see section on thin film papers

19 Co-Ni hep or ref.: ref.: may be ref.: ref.:

fee; (1), (1), high, (b)+(f): (1), ref.: p 277 p 279 e.g., (6) P 672;

(1),

p 277 100 to 200; see

e.g., (48),

Fig. 5

other

ref.:

(b)(49)

see comments

20Co-P hex.

(50)

see comments50 to 1300

(51)

further

ref.:

(52)

21aCo-Ni-P some values values -.-.

(low coer- civity

electroless films)

discussion

in (53)

from

0.3 to ~100

noted

from

2.0 to ~25

noted;

(53) (uniaxial)

(53)

21bCo-Ni-P hep + fee values isotropic high uncer-

(high coer- civity

electrodeposited

films)

mixture

(54) from

r-^OO in the film

(57) tainty

exists

(55)

(56) hex

(57)

(56) to

r~1000

(58); see comments

plane

(54)

(55)

(56) (58)

(60)

(54) see comments

400 to 1000 (59)
Material Structure Curie Temp.

(°C) Ms

(gauss) «c(oe.)

Hk

(oe.)

Kl(ergs/cc)

*-s

22Ferrite

Films;

data given

for a typical

example:

NiFe2 4

(film)

cubic; a = 8.34 A

(61)

inverse

spinel

585

(3)

270

(3) example;

minimum

value

40

(62)

-63xl03

(3) -26xl0"6

(3)

23Garnet

Films;

data given

for a

typical

example: Y3Fe

5 12

(YIG)

(film)

cubic

a = 12.374

O ±0.005 A

(63)

278 ± 2 (63)

~138

(64)

this film

mentioned

reference

type is in

(65)

~7.1xl03

(66)

-2.22xl0

-6

(67)

10
4. Additional Comments

The following are a series of comments to supplement the data

of Table I.

la. Iron - bcc

Ironfilms occasionally require fairly large drive fields for

magnetization reversal. Coercive forces of several hundred oersteds

are not uncommon, and values approaching 1000 oe. have been

reported (68). Reincke (69), however, exceeds this. He prepared

single crystal films of iron by evaporation onto heated rock salt

crystals. Two films of 25 - 30 A reportedly showed rectangular

hysteresis loops and a coercive field of 4000 oe. A smaller coercive

field of 1700 oe. was found in 2 other films 75 to 100 A thick (70).

Various authors have commented on the oxidation of iron thin

films; for example,

Knorr and Hoffman (71) found that upon removal from the

vacuum system, their iron films displayed a bright, shiny,

metallic appearance, and have retained this luster for 2 years.

This results from the oxide layer that quickly forms on pure

iron. Electrical resistivity measurements indicated that most

of the oxidation occurs immediately upon exposure to atmospheric pressure, with very little further oxidation occurring.

Rosette and Hoffman (72) noted an increasing amount of

oxidation with decreasing film thickness, in their iron films. This

oxidation occurred in spite of a coating of MgF2- Koenig (73) found

that iron films deposited on substrates held at 300 C did not oxidize

appreciably when exposed to the atmosphere. Possibly a thin,

passivating oxide layer is formed at the film surface that prevents

further oxidation (74).

Single crystal iron films can be grown onto the (001) surface of

either NaCl or MgO crystals. The lattice misfit of iron on NaCl is

28%, whereas it is only 4% in the case of iron on MgO (15). The

orientation of crystallites is almost perfect for iron on MgO when the

substrate is held above some critical temperature during the

deposition (75). However, the orientation of ironfilms on NaCl is poor

over the entire temperature range from 20 C to 500 "C (75). A

mixture of orientations occurs when iron films are grown on the cube

faces of rocksalt (12). The mode of epitaxy of iron on MgO is given by

< 001

>Fe " < 001 >Mg0

[ioo]Fe || [110]

11
Therefore, the (001) plane of iron, which contains 2 easy axes of

magnetization, coincides with the plane of the film (76).

lb. Iron-fcc

1. The face -centered cubic form of iron (Y-iron) is stable in the

temperature range between 910°C and 1390 °C (77). There is a

volume increase of ~ 1% as bcc iron changes to fee iron at 910 °C (78).

The transformation temperature drops continuously with increasing

pressure, down to 605 C at 100,000 atmospheres (79).

2. It is difficult to study the magnetic properties of fee iron at

low temperatures because of the phase change that would occur.

However, 2 approaches to keep iron in the fee phase at low temperatures have met with some success.

One method is to alloy the iron with certain other metals, such

as chromium and nickel as in stainless steel. This widens the

stability range and preserves the structure to very low temperatures.

However, the other elements, particularly the chromium, may affect

the measured values of Neel temperature (77).

The other approach is to form a metastable Y phase by

precipitating iron from a solid solution in certain materials - e.g. , in copper, where iron precipitates as an iron-rich fee phase coherent

with the copper matrix. Further details appear in the literature (9)

(77).

3. The magnetic properties of fee iron may be summed up

thusly:

a. At high temperatures,yiron is paramagnetic in its region

of thermodynamic stability and obeys the Curie- Weiss relation

(77).

b. Neutron diffraction studies gave no evidence of an

ordered magnetic state at either room temperature or at 77 K

(9).

c. At very low temperatures, Y iron is antiferromagnetic.

The exact Neel temperature is uncertain, with estimates varying from ~8 °K (9) up to 67 ° ± 2 °K (77).

2a Nickel-fcc

1. A noncrystalline film of nickel may be formed.

a. Electroless nickel, formed by hypophosphite reduction

from acid solution, is reportedly nonmagnetic and amorphous

(59). .

12
b. Films evaporated from high purity nickel onto glass

substrates held at ambient temperatures were reportedly often

amorphous (80); however, heating these films at 450 C for 30

minutes resulted in the formation of the cubic structure.

2. Nickel films are apparently subject to oxidation. Mitchell

(81), p. 356 remarked that a clean nickel surface will be oxidized to a

depth of roughly 20 A, even at low temperatures, when exposed to air

probably whether or not it is protected by a film of silicon monoxide. Neugebauer (16) observed that the magnetization of his ultra-thin

nickel films changed fairly quickly when he opened his vacuum system

to air.

3. Sincle crystal nickel films can be grown epitaxially by vapor

deposition onto (001) surfaces of NaG 1 or MgO crystals. The lattice

misfit is 38% for nickel on NaCl, and 16% for nickel on MgO (15). The

orientation of crystallites is almost perfect for nickel on NaCl, or on

MgO, provided that the substrate is held above some critical temperature during the deposition (75).

Nickel films grown epitaxially on NaCl at elevated temperatures

were shown to exist in a highly strained condition while on the substrate, resulting in a tetragonal distortion of the cubic symmetry of

the film (10). Nickel films grown onto MgO were found very difficult

to remove from the substrate (15).

The condition (mode) of epitaxy for nickel films on the cleaved

surface of MgO crystals is the same as for fee -cobalt (76).

2b. Nickel-hep

Efforts to prove or to disprove the existence of a hexagonal

phase in specially prepared nickel films have prompted a number of

papers and comments. These are included in the section on magnetic

thin film papejrs. Interestingly, Wyckoff (82) states that the cubic

modification of nickel (B-Ni) can be made hexagonal (ct-Ni) by annealing

for several days at 170 C. (Probably bulk nickel is meant.

)

3a . Cobalt -hep

o

1. The hep phase of cobalt is stable below ~420 C, while above

this temperature, the fee phase is the more stable one. However,

both phases may appear in the same cobalt specimen. Prutton (83)

notes that both phases have been detected in specimens of bulk cobalt,

Williams and Sherwood (17) report that their cobalt film had approximately equal proportions of hexagonal and cubic crystals, with no

preferred crystal orientation. Heavens (12) noted that his cobalt films,

epitaxially grown on rocksalt crystals, generally consist of mixtures

of the 2 forms, even when deposited at temperatures above 500 C.

13
2. Cobalt is uniaxial at room temperature, with the c-axis

being the easy direction of magnetization, and all directions in the

basal plane being (^equally) difficult directions of magnetization. At

higher temperatures (e.g. , between about 245 and 325 C, ref. (84)),

the directions of easy magnetization lie on a cone around the c-axis.

At still higher temperatures, (~300 C), the preferred direction lies

in the basal plane.

3. The crystalline anisotropy constant, K\, is strongly

temperature dependent. A 20 C rise in temperature above room

temperature (which might occur during observation of the specimen

in the electron microscope) may reduce Kl by as much as 10% (85).

o .4. Grundy and Tebble (86), using a cobalt foil about 1000 A

thick, noted the change in domain pattern in a hep crystal, between

room temperature to about 300 °C. These changes are related to

changes in value and sign of the crystalline anisotropy constant, and

to rotation of the easy axis of magnetization. Bates and Craik (87)

reported finding complex closure domain patterns on the basal plane

of a cobalt crystal.

3b. Cobalt-fcc

1. The fee phase of cobalt is stable above ~420 C. In hep

cobalt, adjacent layers of atoms in (00« 1) planes are displaced with

respect to each other, but the pattern repeats every second layer. In

cubic cobalt, the (111) planes are similar to those of the (00« 1) planes

of hexagonal cobalt, but the succession of planes is different so that

in the cubic structure the pattern repeats after every third layer (1).

The mechanism of the hep-fee crystallographic phase change is given

e.g. , in ref. (19), p 371. The similarity in the 2 structures goes

hand in hand with the small heat of transition (1). Also, there is a

fairly large temperature hysteresis in the phase transformation.

2. Magnetization curves of fee cobalt crystals in the temperature range 500 to 1000 C were found to be similar to those for

nickel, in that the crystallographic directions in order of increasing

difficulty of magnetization are [111], [110] and [100], and the fields

required to produce saturation are only of the order of a few hundred

oersteds. The material became magnetically isotropic at ~1000 C

(19).

3. There are few reports on the magnetostriction of cobalt at

high temperatures because of experimental difficulties (88).

4. Films of fee cobalt can be prepared by epitaxial growth onto

a freshly cleaved MgO crystal heated above ~430 C. This fee

structure is retained at low temperatures as long as the film stays on

the substrate (76).

14
The mode of epitaxy of fee cobalt on MgO is the following:

< 001

>Co I' < 001 >MgO

„ r

< 76> [lOO]Co H [!00]Mg0

The easy directions of magnetization of fee cobalt crystals are <111>;

no change was observed over the temperature range from room

temperature to ~500 C (86). However, in the case of fee cobalt

films on cleaved MgO, the mode of epitaxy coupled with the thinness

of the film causes the easy direction to rotate from the [ 111 ]

direction to the minimum energy direction in the plane of the film - viz., [110] (76).

5. Doyle (21) observed biaxial anisotropy in the film plane of

his fee cobalt films. His values for K, the biaxial anisotropy

constant, varied for different films from -4. 1 ± 0. 6 x 10^ to

-6. 2 ± 0. 9 x 10^ ergs/cc, in fair agreement with the value of

-7. 1 ± 0. 7 x 105 ergs/cc obtained by Rodbell (89) from ferromagnetic

resonance. Doyle notes that K, the observed anisotropy constant,

is not necessarily K]_, the fourth-order crystalline anisotropy

constant (2 1).

4. Gadolinium

1. Gadolinium displays a broad and diffuse transition from the

ferromagnetic to the paramagnetic state, with a consequently illdefined Curie temperature near 300 K (25). Recent studies (23)

indicate that long range magnetic order disappears at 290 K, in

confirmation of previous measurements of magnetization, specific

heat, and resistivity. However, the zero -field magnetization arising

from short range order disappears only at ~300 K, in agreement

with expansivity and x-ray measurements (ibid).

2. Gadolinium displays a fairly large, strongly fie Id -de pendent

apparent magnetocrystalline anisotropy that persists to temperatures

at least 30 °C above the Curie temperature (25).

3. The easy direction of magnetization near the Curie

temperature is along the c-axis, while at lower temperatures (near

77 K), the basal plane becomes the preferred orientation of the

magnetization (90). A recent investigation of a gadolinium single

crystal by neutron diffraction indicated that it has magnetic moments

aligned parallel to the c-axis above 248 K, while below this temperature, the moments make an angle with the c-axis which reaches a

maximum of 75 at 195 K and approaches 30 at 4 K (91).

15
4. A compound of gadolinium and bismuth, Gd4

Bi^, reportedly

has a Curie temperature of 340 °K (24) -- appreciably above that of

gadolinium.

5. Bitter patterns of ferromagnetic domains on a (1120) face of

gadolinium single crystal, taken at -5°C, were recently reported )92).

Bitter patterns of domains on gadolinium are difficult to obtain in this

region of temperature, and none had previously been reported.

5. MnBi

1. The intermetallic compound MnBi (manganese bismuthide),

at room temperature, has a magnetostriction which is the highest that

has been found in any material except cobalt ferrite (28).

2. The anisotropy at room temperature is quite large -- about

twice that for cobalt (1) -- but decreases rapidly with decreasing

temperature (28).

3. The easy direction of magnetization lies along the c-axis of

the hexagonal crystal, down to a temperature of ~84 K. Below 84 K,

the magnetic moments may rotate to positions in the basal plane,

though studies indicate this rotation to be incomplete (27).

4. In bulk form, MnBi is a permanent magnet material

(Bismanol) having both high coercive force and high energy product.

The bulk material reportedly corrodes easily when exposed to the

atmosphere (93). Magnetic films of MnBi reportedly do not deteriorate when exposed to the atmosphere. These films have been

suggested as a medium for high density information storage (94).

6a. 8lNi-19Fe Permalloy

1. Permalloys are a series of high permeability nickel-iron

magnetic alloys. Two regions of composition are of particular

interest -- the 50% nickel region, because the induction is at a maximum (thereafter decreasing with increasing nickel content), and the

81% nickel region, because of its low crystalline anisotropy and zero

magnetostriction.

2. Most past research on magnetic films for use in computer

memories has been confined to the 8lNi-19Fe composition, largely

because of its nonmagnetostrictive property. This property is

desirable for practical applications so that stresses applied to the filmbearing substrate by mechanical or thermal means do not adversely

affect the magnetic properties of the films (29).

o 3. When 81 permalloy, ^1000 A thick, is deposited onto a glass

microslide or cover-glass surface (free from scratches and other

gross imperfections) at a uniform substrate temperature of 300 C,

a value of H^ ranging from 2. 5 to 5 oersteds can be had, with an

16
angular dispersion, a,Q()» of 3 degrees or less (29). Hc typically

varies from 0. 5 Hk to 0. 9 H^, depending on various geometrical

factors and deposition parameters (ibid).

4. In order to obtain zero magnetoelastic strain sensitivity in

Ni-Fe films, the melt must be 83:17 or 81:19, depending whether an

alumina or silica crucible is used (37). This indicates one reason why

results vary between different research groups.

5. Permalloy films, protected from oxidation with a layer of

Krylon (a proprietary acrylic ester resin solution) have been kept

at room temperature for years without changes in Hc or H^. (29).

However, very little work has been published on the effects of elevated

temperatures and weak fields, under vacuum or in air (ibid). Early

findings in an aging study designed to determine the reliability of thin

nickel-iron films of 81%- 19% composition appears in reference (99).

6. The orientation of crystallites is almost perfect for permalloy on NaCl when the substrate is held above some critical

temperature during the deposition (75).

6b. 50Ni-50Fe Permalloy

1. Compared to 8lNi-19Fe, the 50Ni-50Fe permalloy composition has higher values of saturation magnetization, coercive

force, and crystalline anisotropy. It also has appreciable magnetostriction.

2. The possibility of having appreciable compositional

variation between the magnetic film and the starting material should

be noted (18). In addition, permalloy compositions below ~ 50%

nickel begin to show second phases.

3. The coefficient of expansion of ordinary microscope slides,

which is probably in the range 8 - 10 x 10"° per degree C, compares

well with that of the 50Ni-50Fe alloy, which is about 9. 7 x 10"° at

comparable temperatures (18).

6c. 3Ni-97Fe

1. Evaporated or plated permalloys tend to be anisotropic;

however, experiments with the composition 3Ni-97Fe indicate that it

could be electroplated onto a flat copper substrate with essentially

isotropic properties (31).

2. A thin organic coating is used to protect the iron-rich

magnetic film from corroding (33).

17
7. Fe-Ni-Al

Alloys containing nickel, iron, aluminum, perhaps cobalt, and

perhaps small percentages of copper and/or titanium, form the class

of permanent magnet materials known as alnicos. Some compositions

are listed in, e.g., (3), p5-188.

8a. 80Ni-17Fe-3Co

1. This ternary alloy composition had been referred to as

"gyralloy" in earlier publications (34).

2. The specific use of 3% cobalt (by weight) is reportedly a

compromise between increasing values of H^, and decreasing easy

axis angle skew, with increasing cobalt content (34).

8b. 57Ni-13Fe-30Co

This ingot composition lies within the so-called "perminvar

region" (1), Fig. 5-79 -- i.e. , the region of Ni-Fe-Co compositions

for which the typical perminvar characteristics can be developed.

8c. 48. 6Ni-2.8Fe-48. 6Co

Films made from this melt composition reportedly have small

angular dispersion (37).

8d. 45Ni-30Fe-25Co

1. An alloy consisting of 25% cobalt, 45% nickel, and the

balance, iron, corresponds to the usual perminvar composition (1).

However, note that a wide range of alloy compositions in the Ni-Fe-Co

system can exhibit perminvar properties (1), Fig. 5-79.

2. Perminvar characteristics include the following:

a. A low but constant initial permeability up to an induction

as high as 1000 gauss or more, and virtually no hysteresis loss

in this region (95).

b. A wasp-waisted, constricted, or perminvar hysteresis

loop at intermediate values of drive field. The perminvar loop

is usually a minor loop; when the major loop is traced, the

constriction is absent or greatly reduced in magnitude (95). The

perminvar loop may be modified or often eliminated by proper

heat treatments.

8e. Ni-Fe-Co (other)

Cobalt, when added to nickel-iron alloys, raises the value of H^,

but generally lowers the value of Hc in the concentration range to

30% cobalt in the film, and Ni/Fe ratio = 4.9 (48), Fig. 6. (Also

18
see section on magnetic thin film papers. )

9. Ni-Fe-Cr

Chromium is particularly effective in lowering the Curie points

of nickel-iron alloys, especially when the nickel content is high.

This fact is often used in making non-magnetic alloys for special

purposes (1).

11. Ni-Fe-Mo

1. Since molybdenum has a melting point that is so much

greater than that of nickel and iron, it is very difficult to control the

preparation of alloys of these three elements in thin films (29).

Blois (18) discussed the probable compositions of evaporated films

as compared to that of the starting material. In the case of 4-79

moly-permalloy (4Mo-79Ni-17Fe) maintained at 1600 °C, the theory

indicated that the nickel would evaporate about 50% faster than the

iron, but the molybdenum would scarcely evaporate at all. However,

his results with Ni-Fe alloys indicated that the difference in

composition between the film and the melt may be considerably less

than indicated by this theory.

Williams and Sherwood (17) report a chemical analysis of a

150 A film obtained by evaporating the alloy 5%Mo, 79%Ni, 16%Fe,

using a helical tungsten filament, and a pressure of ~10~5 rnm Hg.

The resulting film composition was 7%Mo, 57%Ni, 36%Fe.

2. Attempts to electroplate 4-79 moly-permalloy films have

been disappointing (29).

3. Moly-permalloy films reportedly showed room-temperature ferromagnetism even at a composition estimated at 60% molybdenum (40). This is quite different from that reported for bulk,

where the induction in high fields, at room temperature, decreases

uniformly with increasing molybdenum content, and approaches

zero at about 15% molybdenum (1), p. 136.

4. The composition 5Mo-79Ni-15Fe—-2 Mn, known as supermalloy, results in the highest permeability, lowest coercive force

of any commercially produced material (7).

12. Ni-Fe-P

A few comments concerning the properties of Ni-Fe-P films

appear in the next section on magnetic thin film papers -- e. g. , reference (96).

19
13. Fe-Al

1. A tutorial description of the ordering processes in the

aluminum-iron system is noted in reference (42), p. 144. A model

is shown which indicates that, at the alloy composition corresponding

to the formula Fe3Al, for slowly cooled alloys, the centers of alternate small cubes of the bcc lattice are occupied almost completely by

aluminum atoms, with the other positions in the lattice being occupied

almost completely by iron atoms.

2. Although only one reference to aluminum-iron thin films

has been noted, there have been a fairly large selection of papers

concerning the properties of bulk aluminum-iron specimens.

Interested readers may refer to, e.g. , references (43) or (44) for

bibliographies

.

3. The composition Fe^Al, containing 2 5 atomic percent

aluminum, corresponds to about 13. 83% aluminum by weight.

14a. 50Fe-50Co

1. A number of papers in the literature mention use of

magnetic thin films of iron-cobalt. Two compositions are singled out

for special mention here: 50Fe-50Co because it corresponds to the

permendur composition, and 5Fe-95Co because of its reported use in

a magnetic storage device.

2. The highest value of saturation induction for any magnetic

material, 24, 600 gauss (1), occurs at about 35% cobalt, 65% iron;

however, the plot of saturation induction versus cobalt content is

rather flat over the range 30% to 50% cobalt.

3. Supermendur is an alloy containing 2% vanadium, 49%

cobalt, and remainder, iron. This is an improvement over the 50-50

alloy in everything except maximum induction (7).

4. See comment for 14c. , Fe-Co (other).

14b. 5Fe-95Co

1. Iron-cobalt alloy films, such as 5Fe-95Co, oxidize even

more rapidly than do films of 81-permalloy, unless they are protected

by encapsulation. This occurs even for films 2000 A thick (29).

2. An alloy composition 96. 5%Co, 3. 5%Fe, is reportedly nonmagnetostrictive (29).

3. A phase change from hexagonal to fee occurs at about 95%Co,

5%Fe, at200°C (1), p. 15.

20
14c. Fe-Co (other)

Fairly large values of magnetostriction exist in the iron-cobalt

alloy system. In moderately high fields, there is an unusually large

expansion of 60 to 90 x 10~° in alloys containing 40-70% cobalt.

(A X of 130 x 10"°° was observed in specimens of hard rolled tape

containing 70% cobalt, 30% iron (I), p 664). The magnetostriction

drops to near zero at near 90% cobalt.

19. Co-Ni

1. The magnetic properties of the cobalt-nickel alloys

reportedly have no interesting peculiarities (1); they are rather the

result of mixing 2 elements that are similar chemically and different

magnetically, in that one has almost three times the saturation

magnetization of the other.

2. Magnetostriction: See comment 2 in section 21b, (Co-Ni-P).

20. Co-P

1. The phosphorus content of these films may often be rather

small; e.g. , SalloandCarr (51) used a phosphorus content in the

deposit in the range of 2-3%. Fisher (97) had about a 4% phosphorus

content in his cobalt coatings.

2. The following results were reported (51): The 60-cycle

hysteresis loop of the electrodeposits at all coercivities within the

test range (50 to 2000 oe) showed a squareness ratio (B r /Bm) of about

0. 5. Remanence values were about 5500 gauss for a 400 oe. deposit;

however, full saturation may not have been reached.

21. Co-Ni-P

Films of Co-Ni-P can conveniently be divided into 2 categories.

One category, designated as "21a", consists of electroless films

which, (it turns out), usually have low values of coercive force. The

other category, noted as "21b", consists of electrodeposited films

which, though of similar composition, are known to possess very high

coercivities (53). A recent bibliography of papers concerning Co-NiP films appears in reference (53).

21b. Co-Ni-P

1. Smaller flux outputs were obtained from both the Co-Ni-P

and the Co-P deposits than would be expected from the chemical

composition (51).

2. Bate and Speliotis (54), in discussing their hard films of

Co-Ni-P, mention that the state of knowledge of magnetostriction even

in bulk alloys of Co-Ni is chaotic.

21
3. The addition of phosphorus to Co-Ni alloys reportedly

increases Hc of the deposit (48), Fig. 5.

4. These Co-Ni-P films, as well as the Co-P films, are

usually relatively thick films, compared to typical permalloy

memory films.

22. Ferrite Films; 23. Garnet Films

Tutorial articles on ferrites and garnets, and their actual or

potential applications, are available in the literature -- e.g. , (98).

5. Research Activity Using the Less Frequently-Mentioned

Magnetic Thin Film Materials

This section describes some of the work published using the less

frequently mentioned magnetic thin film materials. All categories are

included except la, (Iron-bcc); 2a, (Nickel-fcc); 3a, (Cobalt-hep);

and 6a, (8lNi-19Fe). The latter-mentioned materials receive frequent mention in the literature; e.g., in the Magnetic Materials

Digest series (100), (101), (102), (103), the writer noted about 46

papers mentioning iron films, 88 mentioning nickel films, and 26

mentioning cobalt films (some possibly fcc-cobalt). Tutorial type

articles dealing mainly with 81-permalloy thin films are available

in the literature - e.g. reference (104).

la. Iron-bcc

See introductory comments to this section.

lb. Iron-fee

u Hasse (105) obtained very good thin (10 A) epitaxial films of fee

iron by evaporating iron onto the (100), (110), and (111) faces of

heated copper single crystals (100).

JCoritka (106) reported that he was able to make Y-iron films up

to 80 A thick, stable at room temperature.

2a. Nickel-fcc

See introductory comments to this section.

2b. Nickel-hep

Bonnelle and Jacquot.(107) found by electron microscopy and

diffraction, a hexagonal phase on annealing vacuum deposited nickel

films (102). Trillat et al (108) made general observations concerning

the transformation of fee nickel to the hexagonal form. The hexagonal

form reported by Bonnelle and Jacquot is questioned, since the

lattice constants of Ni3C and Ni3N are so close to that found for

22
hexagonal nickel, as seen below (70):

Material a c

Ni (hex) ? 2. 63 ± 0. 01 A 4. 32 ±0.02 A

Ni

3

C 2. 628 4.306

Ni

3

N 2. 660 4.304

Thin films of nickel reportedly were transferred from the fee lattice

into the hep lattice as a result of fast neutron irradiation (109). All

irradiated samples showed great changes in magnetic properties.

The magnetic properties disappeared for the samples that completely

transformed into the hep structure. Gaertner (110) prepared nickel

layers by cathodic sputtering. When atmospheres of spectroscopically pure nitrogen and tech. argon were used, x-ray diffraction

lines of hexagonal Ni3N appeared; however, these lines were not

present in such layers formed in spectroscopically pure argon

atmosphere. In the last case, the nickel lattice constant is 3. 52 A,

which is that of pure nickel (70). The results suggest (102) that the

extra electron diffraction lines, sometimes found in sputtered nickel,

are probably caused by Ni3N, and not by hexagonal nickel as reported

earlier.

Morimoto and Sakata (111) evaporated nickel films with mean

thickness about 10 A, onto amorphous substrates. The evaporation

and heat treatment were carried out in the diffraction camera.

Although all diffraction patterns of these nickel specimens showed

a fee structure, anomalous neighbors of the hep type were also found

in the nickel crystallites.

Several investigators reported failure in efforts to find a hexagonal phase in nickel thin films. Jhese include Neugebauer (16)

who prepared thin nickel films ( < 100 A) in ultra high vacuum

(~ 10~9 mm Hg. ); Heavens (12) who grew epitaxial nickel films on

rocksalt, and Adamsky and Sears (80) who prepared amorphous

nickel films by evaporating pure nickel onto glass substrates held

at ambient temperatures; however, they (80) note that no effort was

made to study extremely thin films where possibly a hexagonal nickel

structure is stable.

3a. Cobalt-hep

See introductory comments to this section.

23
3b. Cobalt-fcc

L. Reimer (112) prepared thin cobalt layers by electrodeposition onto a copper surface. Electron diffraction showed the

layers to have a purely cubic structure. A maximum in coercive

force was found at 20° and at -190 u

, for thicknesses of 200 and 300 A

respectively. The corresponding coercive forces were 350 and 600 oe

(70).

O.S. Heavens (12) found that cobalt films prepared on rocksalt

generally consist of mixtures of hep and fee structures, even when

deposited at temperatures above 500°C Frait (113)made ferro-

magnetic resonance measurements on thin cobalt films that were

vacuum deposited onto unheated glass slides. The line width and

other resonance parameters were obtained as functions of filrn^

thickness. An fee structure was found for films 600 and 1200 A thick.

Tannewald and Weber (114) measured the exchange constant A,

and exchange integral J, and their temperature dependencies, in

evaporated cobalt films, using spin wave resonance. At room

temperature, A = 1. 30 x 10"" erg/cm, and J = 155k (ergs). The

results are compared with data obtained by other methods. The

cobalt films showed a predominantly cubic structure, a uniaxial

anisotropy of ~ 23 oe in the plane of the film, and a g factor and

saturation magnetization close to that of the bulk.

Rodbell (89) prepared single crystal fee cobalt films on MgO

substrates. Standard ferromagnetic resonance techniques were used

to determine the magnetocrystalline anisotropy parameters K^/M and

K2/M over the temperature range 4. 2 - 850 K.

Morimoto and Sakata (111) made structure studies of ultra-thin

nickel films and cobalt films formed on amorphous substrates. These

films, of average thickness 10 to 20 A, are not continuous, but consist

of small crystallites. The results for cobalt films deposited on 20 C

substrates implied a possible mixture of hep and diamond structures.

Heating these films tended to favor the hep structure. Cobalt films

deposited on substrates at 450°C showed fee type diffraction patterns

that did not change when the films were cooled to room temperature.

Sato et al (76) observed a checkerboard domain pattern on a

single crystal fee -cobalt film epitaxially grown on a heated M

g substrate.

Grundy and Tebble (86) examined the domain structure in thin

cobal£ foils at temperatures above room temperature. The foils were

1000 A thick, and contained both fee and hep phases. At higher

temperatures, the domain pattern in the fee regions was in agreement

with anisotropy measurements.

24
Doyle (21) extended the Stoner - Wohlfarth coherent rotation

model to the case of biaxial anisotropy, and compared some of the

predictions with experimental results observed on fee single -crystal

cobalt films. The films were prepared by epitaxial evaporation onto

the (100) face of single -crystal MgO slabs held at ~400°C. Torque

and rotational hysteresis measurements on these films yield some

results in disagreement with the theory. It is concluded that the

magnetization reversal process in single-crystal cobalt films is not

coherent, and that noncoherent rotations or wall motions must be

investigated.

4. Gadolinium

Holmes and McClung (115) prepared evaporated films of iron,

nickel, cobalt, and gadolinium. Faraday rotation measurements for

iron, nickel, and cobalt are reported. However, the gadolinium films

did not show any rotation at temperatures as low as 77°K.

Wilburn (116) evaporated Er, Yb, Ho, Tb, Gd, and Tm on

quartz and glass substrates as optical film surfaces. Vacuum

evaporation techniques are discussed. Optical properties of these

metals are presented (70).

Auphan (117) reported measurements of the Kerr magnetooptic

effect made on thin films of gadolinium overcoated with a protective

film of silicon monoxide. He observed that the effect diminished with

temperature somewhat more slowly than expected (102).

SchuTer (118) describes briefly the construction of an all-glass

electron diffraction camera. It was found possible to obtain pictures

of the clean surface of thin gadolinium films evaporated at a residual

gas pressure of 10 7^ mm Hg. inside the camera, and to follow the

oxidation process taking place at somewhat higher pressure.

Schiiler (119) lists measurements of the longitudinal Kerr effect

on thin gadolinium films, prepared and measured in ultra high

vacuum.

Schiiler (120) presents a study of magnetoresistance in thin

evaporated gadolinium films. The films were prepared in ultra high

vacuum, and the temperature dependence of the resistivity was

measured between 80 K and 450 K. Results are compared to that

reported for bulk.

Schiller (121) examined the spin ordering effects in the

electrical resistance of thin films of Gd, Dy, and Tb.

Lambeck et al (122) report the detection of the Faraday effect

in thin evaporated layers of gadolinium. Hysteresis curves were

obtained with the help of the Faraday effect and the Kundt constant.

25
The dc voltage generated across the surface of a thin magnetic

film during ferromagnetic resonance provides a new and' sensitive

means of studying ferromagnetic resonance phenomena (123).

Juretschke (124) reported on further studies of this effect, using thin

films of nickel and of gadolinium.

A report (90) dated April 1963, noted that efforts to make thin

film single crystals of gadolinium had not yet proven successful.

5. MnBi

Thin films of MnBi were reported (125) (126) in which the c-axis

of the hexagonal crystallites (which is also the axis of easy magnetization) tends to be normal to the plane of the films. The films, ~1000 A

thick, gave an optical rotation of ~ 5 for transmitted light, providing

good visual contrast for observing the domains by means of the Faraday

effect (95). It is possible to write magnetically on these films with a

fine permanent -magnet probe, and to read the writing with the

polarized-light technique.

Mayer (127) (128) suggested that writing could be done by heating

a small region of the MnBi film above the Curie point, using an

electron beam. On cooling, the fringing field from the surrounding

film would cause this region to have a reversed magnetization. This

process is called "Curie point writing". The direction of easy

magnetization must be normal to the plane of the film; however, this

is possible despite the large demagnetizing fields.

4 Mayer (94) found that writing speeds corresponding to 3 x 10

bits/sec. , and information densities corresponding to 10^ bits/cm

were achieved in first experiments using Curie point writing on MnBi

films. Considerably higher writing speeds (106 bits /sec. ) and some

increase in information density (10° bits/cm^) should be feasible

(ibid). Readout is possible by use of the Kerr magneto-optic effect,

or the Faraday effect, or electronically, by electron mirror microscopic methods. Two major difficulties were encountered with MnBi

films (93). One difficulty is that of erasing, since this requires the

application of several thousand oersteds. The other difficulty is the

poor reproducibility in the preparation of these films -- e.g. , films

may turn out to be nonmagnetic, or to have, at least in part of the film,

the direction of magnetization in the plane of the film, rather than

normal to it. At least 2 papers (93), (129) have been concerned with

the problem of reproducibility.

Chen and Gondo (130) examined the magneto -optic Kerr rotation

and the crystalline anisotropy energy of MnBi films over the temperature range 84 °K to 300°K.

26
6a. 81Ni-19Fe

See introductory comments to this section.

6b. 50Ni-50Fe

This material was used occasionally in research on magnetic

thin films. Blois (18), in his classic paper on the preparation and

properties of thin magnetic films, noted the effects of annealing on the

coercivity of a series of 50Ni-50Fe films. JRubinstein and Spain (131)

prepared a film from a 50Ni-50Fe ingot for their studies of cross -tie

walls in thin films. Fuller and Hale (132) mention use of a 50Ni-50Fe

alloy film in their paper concerning the use of transmission electron

microscopy to observe the magnetization pattern in magnetic th'in films

Kirenskii et al (133) observed the domain configurations in films of

Fe, 50Fe-50Ni, and 80Ni- 17Fe-3Mo with the Kerr effect, from -15°C

to 650°C (103). Fuller and Rubinstein (134) proposed methods using

domains at a high density in a continuous film for storing information

in compact, large -capacity memories. A wall-film interaction

experiment is described using a multi-layered structure consisting

of a relatively high coercive force (14 oe. ) 50Ni-50Fe film, separated

from a low coercive force (2 oe. ) 80Ni-20Fe film by a film of MgF^.

6c. 3Ni-97Fe

Kolk and White (33) discuss the effects of various deposition

parameters on the resulting magnetic properties of 3Ni-97Fe thin

film electroplate. Optimum magnetic properties were achieved for

use in the Rod magnetic memory device.

Bobeck (31) reported use of this alloy composition in part of the

cubic waffle iron memory device. When the 3Ni-97Fe material is

electroplated to a thickness of 0. 05 thousands of an inch, it has a

coercive force of 9 oe. , a squareness ratio of 0. 95, and a switching

coefficient (Sw) of 0.8 oe-p.sec.

7. Fe-Ni-Al

Hodges (135) reported on a study into the influence of directional

ordering on the anisotropy of magnetic thin films. Although most of

his work appears to have been with aluminum iron alloy thin films, he

observed that the anisotropy of permalloy films could be governed by

an oblique incidence aluminum beam, and that the easy axis so formed

could be made to lie orthogonal to the direction of an applied annealing

field.

A typical example is mentioned in which a permalloy film containing near 3 atomic percent aluminum, had an equivalent anisotropy

field aligned by the aluminum beam, of 22 oe. , with an easy axis

direction coercive force of 0. 9 oe..

27
8a. 80Ni-17Fe-3Co

A number of papers have appeared recently mentioning use of

Ni-Fe-Co films evaporated generally on an aluminum substrate, _/

from a starting ingot composition of 80%Ni, 17%Fe, 3%Co, by weight.

Bradley (34) considered the properties that magnetic films

should have, in order to function successfully in computer memories.

Particular importance is attached to reducing the easy axis

dispersion. His considerations suggest use of this nonmagnetostrictive composition on an aluminum substrate as a possible

compromise solution to the problem.

Leaver and Prutton (136) reported on inhomogeneous coherent

magnetization rotation in these films. Leaver (137) noted the

dependence of the easy axis dispersion on film thickness. He found

the dispersion of these £ilms remains at ~ 1 , for film thicknesses

between 2000 A to 6000 A, if a substrate temperature of 150 C was

used (103).

Mossman and Williams (35) note that a principle factor in the

failure of magnetic film storage elements is skew of the easy axis.

Since the skew varies from one film element to another, they

investigated the way in which such variation affects the performance

of storage cells. One effect noted is that the films may become more

sensitive to small disturb pulses.

Leaver and Prutton (133) proposed a theory of reversal which

is in qualitative but not quantitative agreement with experimental data

obtained on Ni-Fe-Co films (70).

Fuller and Lakin (139) performed wall-wall interaction experiments. They used vacuum deposited, double -layer films of 100 A

thickngss, prepared from 80Ni- 17Fe-3Co material, and separated by

a 100 A layer of carbon. The multifilm structure was thin enough so

that transmission electron microscopy could be used to see domain

walls in both films simultaneously.

Bonyhard (140) used this ingot composition in his investigation

of the switching behavior of thin ferromagnetic films at liquid helium

temperatures, using fast pulse techniques.

8b. 57Ni-13Fe-30Co

Tickle (36) prepared films evaporated from ingots of this

composition (by weight) in the development of a domain wall motion

V

Use of a. thick, high conductivity substrate has many advantages.

However, 2 disadvantages are considered in reference (199).

28
shift register. He defined the nucleation factor as the ratio of the

writing field (the minimum field required to introduce reverse

domains into a saturated film) to the shifting field (the minimum field

required to move the walls of an already existing domain). A large

nucleation factor is desirable for this application; however, this is

difficult to achieve with permalloy films (ibid). The Ni-Fe-Co

composition provides a reasonably large nucleation factor for the

shift register application while still providing zero magnetostriction.

8c. 48. 6Ni-2.8Fe-48. 6Co

Crowther (37) considered 2 methods for achieving higher bit

densities in magnetic thin film memories. One approach uses

conventional Ni-Fe films in a paired film structure which has quasiflux closure in both the easy and the hard axis directions. The other,

more direct approach simply uses a film with a higher coercive force

and no magnetoelastic sensitivity, such as the above (melt)

composition.

A slightly different melt composition -- approximately 47%Ni3%Fe-50%Co -- was mentioned in another paper which considered this

problem (141). These films also featured Hc = 10 oe. , Hk = 30 oe. , low angular dispersion, and essentially zero magnetostriction.

8d. (Perminvars)

Perminvar films were used occasionally in research on

magnetic thin films. Conger and Essig (142) presented a theory

correlating the ferromagnetic resonance line width with the reversal

time of thin films, for reversing fields greater than a certain critical

value. Experimental results with film compositions of 80Ni-20Fe;

48Ni-30Fe-22Co; and 85Co-15Fe gave support to the theory.

Williams and Sherwood (17) examined domain patterns in thin

films deposited from 43Ni-34Fe-23Co perminvar onto a heated substrate in the presence of a magnetic field. Gomi et al (143) studied

domain patterns on films prepared by evaporating perminvar

(45Ni-30Fe-25Co) on unheated substrates, in the absence of an

external magnetic field.

Heidenreich and Reynolds sought to correlate the microstructure

of magnetic thin films with their magnetic uniaxial anisotropy.

Results indicated (144) that both bulk and thin film perminvars and

permalloys contain oxygen atoms condensed along (111) planes when

they also exhibit a uniaxial anisotropy (83). These faults form

preferentially with their normals parallel to the induced anisotropy

(83).

29
8e. Ni-Fe-Co (other)

Wolf (145) discussed the electrodeposition of alloys of the Ni-Fe - Co system. Solutions from which these metals are deposited are

described and the role of their constituents discussed. The variation

of magnetic properties with cobalt content is shown. Results indicate

that the magnetostriction coefficient depends only on the Ni-Fe ratio in

the films

.

Bradley (34) presents some quantitative data on vapor deposited

Ni-Fe -Co films. The zero magnetostriction composition is plotted

for increasing cobalt content, running from 8lNi-19Fe at 0% cobalt

content, to about 45Ni-10Fe at 45% cobalt content. H^ values rise

linearly with increasing cobalt content up to 35% cobalt (thereafter

leveling off) while the Ni:Fe ratio is maintained to keep zero magnetostriction.

Bruyere et al (146) studied a new type of magnetic interaction

between 2 ferromagnetic thin films separated by a third metallic, nonmagnetic thin film. This coupling tends to bring the magnetization of

the ferromagnetic materials parallel. The coupling depends upon the

materials and the thickness of the intermediate material. Nonmagnetostrictive alloys, such as 45Ni- 10Fe-45Co or 52Ni-13Fe-35Co,

were used for one of the films in the multifilm structure.

Massenet (147) described experiments on multilayer evaporated

thin films with a structure FeNi-Mn-FeNiCo, and FeNi-Mn. There

was strong evidence of a ferromagnetic - antiferromagnetic exchange

coupling between the FeNi film and a transition layer at the FeNi-Mn

interface obtained by mutual diffusion of Mn and FeNi at 300 C.

A 52Ni-13Fe-35Co composition was mentioned.

9. Ni-Fe-Cr

Cohen (39) prepared vacuum deposited Ni-Fe-Cr films on heated

glass substrates. The Cr content ranged from to ~ 5%, while the

Ni:Fe ratio ranged from 78Ni-22Fe to 90Ni-10Fe. For all Ni-Fe

ratios, the anisotropy field H^, the magnetization M, and the wall

coercive force Hw decreased monotonically with Cr content, while

angular dispersion and electrical resistivity p increased with Cr

content. The variations of M and p with Cr content were consistent

with bulk data (ibid).

10. Ni-Fe-Cu

Wolf (148) examined the effect of increasing copper content in

Ni-Fe-Cu films, on the properties of the films. The magnetization

at room temperature is plotted against increasing copper content. A

linear decrease in magnetization is shown, similar to the quenching

effect noted in bulk Cu-Ni.

30
11. Ni-Fe-Mo

Williams and Sherwood (17) observed domain patterns on

evaporated films of iron, nickel, cobalt, and several alloys, including

Ni-Fe-Mo. Kirenskii et al (149) studied the magnetization in molypermalloy and the magnetic anisotropy of cobalt films (102).

Kim and Rodichev (150) measured the wall velocity in iron and

in Ni-Fe-Mo films for cases in which the entire film switched in one

jump. A plot of wall velocity versus applied field resulted in a

s traight line with a positive intercept on the field axis. In the case of.

Ni-Fe-Mo, the slope was 3.432 x 104 cm. sec. "** oe. ~ , with an

intercept of 3.8 oe. (103).

Kirenskii et al (151) studied the domain structure of Ni-Fe-Mo

films in the temperature range - 100 to 700 U C. They found no

appreciable change in domain structure, but the nucleation field and

the saturation field were found to increase with decreasing

temperature (103).

Eckardt (152) prepared Ni-Fe-Mo films by normal incidence of

Ni-Fe vapor, but angular incidence of Mo vapor. The resulting films

showed anisotropy in the plane and perpendicular to the flux of Mo

vapor (103).

Telesnin et al (153) made pulse switching measurements on Mopermalloy films (103).

Ahn and Beam (40) prepared molybdenum -permalloy films using

two evaporating sources; one contained 83Ni-17Fe by weight, and the

other contained pure molybdenum. Intrinsic film properties

measured at Mo concentrations up to 6% - 8% indicated reductions

of M, Hc , Hk> and dispersion. However, at high Mo concentrations,

oblique incidence produced strong anisotropics.

12. Ni-Fe-P

Freitag et al (96) discussed the magnetic properties of ternary

alloy Ni-Fe-P films as a function of their composition and thickness.

They prepared essentially nonmagnetostrictive films, 1200 A thick,

and 3x3 inches in area, with coercivities of 2 oe. and anisotropy

fields at 3. 5 oe. The Ni-Fe atomic ratio corresponding to zero

magnetostriction increases from approx. 4. in the absence of

phosphorus, to about 5. 5 at 3. 2 wt. % phosphorus, for films about

1200 A in thickness. They noted an improvement in magnetic

properties when the phosphorus content was 1% to 2% by wt. ; however,

at higher phosphorus content, the magnetic properties deteriorated.

Kriessman et al (41) considered methods that would result in a low power, thin film memory. One approach is the use of film

31
compositions that have lower values of anisotropy field, Hj^, hence

require smaller values of drive current. They reported use of

essentially nonmagnetostrictive Ni-Fe-P electrodeposited films, ~ 200 A thick, having Hk values ranging from 0. 9 to 1. 4 oe. , compared to 3 to 4 oe. for films in present magnetic film memories.

Matcovich et al (154) describe a memory system presently

under development. The magnetic film spots consist of an electroplated Ni-Fe-P alloy, 5 mils in diameter, and a few hundred A thick.

The reported values of Hc and H^ are about 2 oe. and 1 oe. , respectively; switching is completed in 10 ns. with a word drive

current of 35 ma.

13. Fe-Al

Hodges (135) prepared evaporated films of Fe-Al on glass

substrates. Separate evaporating sources were used because of the

difference in vapor pressure of iron and aluminum. The geometry

of the evaporation was such that, when the iron was deposited at

normal incidence, the aluminum was incident at ~ 30 u to the substrate,

The magnitude of the aluminum beam induced anisotropy was

measured as a function of aluminum content in the film. A specimen

containing an average chemical composition of 22. atomic percent

aluminum had an anisotropy energy density of 1. 5 x 10^ ergs/cc.

This compares with a maximum induced anisotropy of < 1. 8 x 10

ergs/cc in bulk Fe-Al, occurring at about the same 22 atomic percent aluminum composition (43). The results suggest that the easy

axis dispersion found in large area films due to the geometry of the

deposition, may be reduced by the use of suitably oriented aluminum

beams incident over the film area during its deposition (ibid).

14a. 50Fe-50Co

Williams and Sherwood (17) prepared various magnetic thin

film types, including a film made from a 50Fe-50Co alloy in their

study of domain patterns on thin films. Heat treatment in a magnetic

field established an easy direction of magnetization in the film.

14b. 5Fe-95Co

This composition is reportedly used in the Bicore memory

device (29).

14c . Fe-Co (other)

Conger and Essig (142) used an 15Fe-85Co film in their studies

of magnetization reversal in magnetic films.

Kolk and Orlovic (155) used thin films of iron, nickel, cobalt,

and a 70Fe-30Co alloy, in their study of ways to increase the Kerr

magneto-optic effect in thin films. They found that the magneto-optic

32
rotation, of magnetic films of thickness less than 500 A is a function of

the optical properties of the substrate as well as the optical constants

of the magnetic material.

Grycza (156) measured the Faraday effect of thin films of iron,

nickel, cobalt, and an Fe-Co alloy. He found that the "equivalent

magnetization" diminished rapidly at a critical thickness, as compared

to that for bulk samples (70).

15. Ni-Cu 16. Ni-Pd

Nose (157), (158), (159), and Kimura and Nose (45) made spin

wave resonance measurements on various nickel, Ni-Cu, and Ni-Pd

(alloy) films. For Ni-Cu and Ni-Pd films, the exchange coupling

constant, A, decreased monotonically with increasing content of Cu

and Pd, to ~ l/5 at 22% Cu, and 2/3 at 35% Pd, respectively. The

exchange integrals, J, of these alloys were, however, nearly constant.

The temperature variations of A and J are investigated for some Ni-Cu

alloy films (159).

17. Nickel alloy films; miscellaneous

In addition to the nickel alloy thin films already mentioned,

various other such films have appeared in the literature from time to

time, generally for studies concerning other than magnetic properties.

A sampling of these papers aow follows.

Fukano (160) prepared quenched single crystal films

of Ni-Au alloy. He studied the structure changes prompted

by various aging processes. (Some magnetic properties of

bulk Ni-Au samples appear in reference (161) ). Flechon and Ormancey (162) made resistivity measurements of P (2-12%) -- Ni films as a function of tnickness,

to provide a method for determining the P concentration (70).

Goto et al (163) describes the manufacturing processes

and the properties of vacuum deposited Ni-Cr alloy thin film

resistors.

Finnegan and Gould (164) studied Fe-Ni, Ni-Cr, and Pb-In

alloys by the moving-plate technique, to determine deposition

rates during vacuum evaporation to prepare homogeneous alloy

films (70).

Vaumoron and Colombani (165) reported on qualitative

investigation on the evaporation of a nickel chromium mixture

(thin film) (166).

33
18. Co-Cu

In the binary system Co-Cu, no thermodynamically stable solid

solutions exist at any temperature in the concentration range between

12 and 95 at. % Cu (167). However, Kneller (167) reports the

successful preparation of metastable solid solutions in the concentration range 40 to 85% Cu, by the simultaneous evaporation of Cu and

Co onto a substrate kept cool enough to prevent decomposition. The

metastable solid solutions were in the form of polycrystalline films ~ 1000 A thick.

The thermodynamic equilibrium state (2 phases) could then be

obtained by subjecting the film to high temperature vacuum annealing.

Spin moment measurements are shown both for the metastable asdeposited alloy, and for the 2 phase system after annealing. The

latter corresponds to an equilibrium mixture of Cu and j?0Co- lOCu.

S. Mader et al (168) prepared Co-Cu films 600 to 1000 A thick, by

the simultaneous evaporation of the 2 metals in vacuum. When alloys

of 40-65% Cu were prepared by co-evaporation onto substrates at

room temperature or at 80 K, the diffraction pattern always indicated

a metastable single phase solid solution, in complete agreement with

the magnetic studies of Kneller (167).

The structure of alloys prepared by the "vapor -quenching"

technique mentioned above, were compared with that obtained by the

rapid quenching of the liquid alloy solutions. The authors conclude

that for Co-Cu (and for Cu-Ag), the method of vapor quenching onto a

cold substrate is considerably more effective for the production of

nonequilibrium phases than is the liquid -quenching method.

19. Co-Ni

Boyd (6) measured the crystalline anisotropy constant K^ of

epitaxially grown single crystal films of Ni, Fe, Ni-Fe, and Co-Ni

alloys, using a sensitive torque balance. The resulting values of Ki

are compared with previously published data taken on bulk single

crystals. The Co-Ni alloy films are not in good agreement as to the

magnitude of Kj_, but do show the same variation with composition

(ibid).

L. Reimer (148, discussion section) mentioned experimenting

with electrodeposited Co-Ni films on copper substrates. The films

showed, at low cobalt content, a much higher content of twins.

Fuller and Sullivan '(169) examined, both theoretically and

experimentally, the magnetostatic interactions between 2 parallel

Neel walls in 2 parallel planes (103). They mention use of a vacuum

deposited multi-layer film consisting of a 50Co-50Ni film separated

from an 8lNi-19Fe film by a film of MgF2

, in their experimental

studies.

34
E. Hirota (170) reported use of a 90Ni-10Co alloy film, 1500 A

thick, in a spin wave resonance experiment.

20. Co-P

Sallo and Carr (51) discussed means of preparing Co-P electrodeposits having a wide range of magnetic properties. Studies of the

crystalline structure of the deposit are given, along with an interpretation of the origin of the coercivity. Further studies of these high

coercivity electrodeposits, as well as Co-Ni-P electrodeposits,

appear in references (50) and (59). Both rod and platelet particles

were found in the electrodeposits. The high coercive force was

attributed to crystalline anisotropy in the case of the platelet structures,

and to shape anisotropy in the case of the rod structures (59).

Fisher (97) studied the recording characteristics of Co-P fi^ms

prepare^ by electroless deposition. Film thicknesses from 3000 A to

56,000 A were used. The hysteresis, saturation recording and surface

characteristics are compared to commercial oxide tapes evaluated

under identical conditions.

Allen et al (171) studied high coercivity Co-P electrodeposits as

a magnetic recording medium in both contact and non-contact recording. Data are given concerning the packing density and signal output

levels that can be expected from these coatings. Also discussed is

the effect of coercive force and deposit thickness on these parameters.

21a. Co-Ni-P (low coercivity electroless films)

Sallo (172) (173) used films of nominal composition 35%Co,

63%Ni, and 2%P, (172) in the fabrication of a thick film, closed flux

path memory device called "orthocore". Electroless deposition was

used because it forms a uniform deposit over the complex geometry of

the device. Coercive forces are low; values ranging from 0.2 oe. to

more than 5 oe. are attainable.

Holmen and Sallo (53) prepared thin ferromagnetic films of

Co-Ni-P by chemical (electroless) deposition. The effects of film

thickness and composition on coercivity and anisotropy are discussed.

Also mentioned are switching data, dispersion data, torque curves,

and effects of various chemical parameters on film properties.

21b. Co-Ni-P (high coercivity electrodeposits)

1. Sallo and Olsen (57) reported a Co-Ni-P electrodeposit having

a 60 cycle coercive force of 1000 oe. Electron micrographs showed

oriented clusters of lamellar structures. The material was found

to be hexagonal, with its easy direction of magnetization (c-axis)

in the plane of the film. Various results are explained on the basis

of a model which considers each lammela to be a single -domain

35
particle. Further studies into the origin of the high coercivity of

these electrodeposits were also reported (50), (59)-

2. Bate and Speliotis prepared hard magnetic films of CoNi-P by electrodeposition onto polished brass substrates (54), (55),

(56). Some statistics on these Co-Ni-P films are given directly

below:

Composition (wt. %) Film

Thickness

H M Reference

Co : Ni : P (microns) (oe.) Ms 85 : 14 1 0. 020 to 3. 375 to 600 ~ 0. 70 to 0.80 54

78 : 20 2 0. 025 to 5 400 to 800 ~0.75 to 0.85 55

78 : 20 2 0. 1 to 15 300 to 700 56

(balance) 20 2 to 3 0. 1200 500 to 1000 0.90 to 0.95 58

85 14 1 0.05 to 0.2 300 to 550 -0.90 60

A combination of properties was reported in these high coercivity

films that is difficult to explain in terms of existing theories of

magnetization reversal. A unique mode of magnetization reversal

was found in these films (60).

22. Ferrite Films

Brownlow et al (174) gave switching and hysteresis data for

ferrite films of ~ 10 microns thickness. The films are considered

for use as storage and logic devices.

9 Ba^nks et al (175) prepared various composition ferrite films

of 1000 A. thickness, by vacuum evaporation of the metals, followed

by high temperature oxidation. They noted that in many respects the

properties of the films are the same as those of bulk ferrites of

similar composition.

Lemaire and Croft (176) prepared ferrite films using a spray

technique whereby hot suspensions cf hydroxides are directed onto

a heated substrate. They noted that coercive force decreased as

film thickness increased.

Wade et al (177) made resonance isolators at 30 Kmc/sec. , using chemically deposited films of nickel and nickel zinc ferrite

about 35 microns thick, deposited onto alumina substrates (103).

Heinz and Silber (178), using thin films of magnetite, Fe304 , observed

the d-c voltage that accompanies ferromagnetic resonance in a ferrite.

The d-c voltage had previously been observed in thin metallic films.

36
Francombe et al (62) measured the Faraday rotation and displayed the "optical" hysteresis loops for NiFe20^. and CoFe204 by

using th^n films of these compounds with thicknesses in the range 1000

to 8000 A. These ferrites in bulk form are opaque even at small

thicknesses (~ 2 mils), and therefore information on Faraday rotation

or optical absorption spectra of these compounds had not previously

been available (ibid).

Gleason and Watson (179) describe the experimental deposition

apparatus, the procedure used to deposit the films, and the resulting

properties of ferrite films of a nickel-zinc -cobalt composition,

prepared by pyrohydrolytic deposition.

Wade et al (65) prepared various ferrite films and garnet films

by deposition from chemical solutions. Preparation techniques,

microwave measurements, and crystallographic structure studies

are discussed for these films. Possible applications in millimetermicrowave ferrite devices are noted.

Ferrite thin films are considered in the development of thin

film spiral inductors (180). An article by Schroder (181) concerns

magnetic oxide thin films (166).

23. Garnet Thin Films

Occasional mention has been given to the preparation of garnet

thin films (65), (175). Wade et al (65) note that their chemical

deposition method has successfully made both spinel ferrites and

garnet ferrites; the amount of the main phase generally ranged from ~ 90 to 100%, while second phases (mostly ferric oxides) when present,

did not exceed 10%.

24. Other

Freitag and Mathias (48) discuss the effect of various preparation variables on the subsequent composition and magnetic properties

of electrodeposited magnetic thin films. Magnetic materials

mentioned include Ni-Fe, Ni-Fe-Co, Ni-Fe-P, Ni-Co, Ni-Co-P,

Co-P, and quaternary alloys of nickel, iron, molybdenum, phosphorus,

and arsenic.

Reference (182) titled: "Magnetic Tape Recording Materials"

lists the physical and magnetic properties of some metals and alloys

in powder and film form, as well as the physical and magnetic

properties of some permanent magnet oxide powders*

37
Table II. Interesting Features and Potential Applications of Materials

Reported as a Magnetic Thin Film.

38
1 Material Interesting Features Applications

la.Iron-bcc The high saturation magnetization of iron,

coupled with its low cost (as bulk) makes

iron an ideal constituent for many magnetic

applications.

The ferromagnetic elements iron,

nickel, and cobalt find applications as a thin film mainly in the form of alloys, rather than

as the pure element itself.

lb.Iron-fcc Uncertainty exists concerning its magnetic

properties at low temperatures.

(not ferromagnetic)

1

2a.Nickel-fcc Nickel films offer an uncomplicated structure (no phase change normally expected)

and a low Curie point; its saturation

magnetization is low, compared to iron.

See remarks for iron-bcc.

2b.Nickel -hep Research efforts have been directed

largely towards proving or disproving the existence of a hexagonal phase in specially

prepared nickel films.

....

!

3a.Cobalt-hep Cobalt (hep) is a strongly uniaxial

material at room temperature, with a large

magnetocrystalline anisotropy. The easy direction of magnetization changes ac higher temperatures.

See remarks for iron-bcc.

3b.Cobalt-fee The high temperature form of cobalt can

exist as a thin film at room temperatures,

under certain conditions.

....

4. Gadolinium Gd displays some interesting properties:

1. an ill defined Curie temperature.

2. a relatively large and highly fielddependent crystal anisotropy at and above the Curie point.

3. a variation of easy direction of magnetization with temperature.

4. an unusuallylarge ferromagnetic Hall

effect (183).

5. a compound with bismuth having a Curie point appreciably above that

of Gd.

39
Material Interesting Features Applications

5.MnBi MnBi displays some interesting properties:

1. a strong f erromagnetism, although its constituents are not ferromagnetic.

2. very large values of magnetostriction and

anisotropy at room temperature.

3. a variation of easy direction of magnetization with temperature.

4. extremely large magneto-optic Kerr rotations found at room temperature in oriented films (130)

.

5. an easy direction of magnetization perpen- dicular to the plane of the film.

Films of MnBi have been suggested

as a medium for high density

information storage (94)

.

6a.81Ni-19Fe

(81 -permalloy)

This alloy film has the following properties:

1. zero magnetostriction.

2. fairly low crystalline anisotropy.

3. fairly low values of Hc and H^.

4. a well developed uniaxial anisotropy with low dispersion.

5. a rectangular hysteresis loop

6. high permeability.

1. magnetic film memories.

2. magnetic film logic devices

(see, e.g., ref. 184)

3. thin film parametric devices

such as parametrons , para- metric amplifiers, balanced

modulators, and flip-flops

(185).

4. sensitive field magnetometer

(186).

5. variable delay magnetic strip

line (187).

6. all-electronic compass (188)

6b.50Ni-50Fe This alloy film was used when higher

coercive force values were desired than

provided by 81-permalloy . Now this

function appears to be taken over by the nonmagnetostrictive Ni-Fe-Co

compositions

.

....

6c.3Ni-97Fe This composition may be useful when

magnetic isotropy is desired. It also

provides a coercive force about an order

of magnitude above that for 81-permalloy.

1. the magnetic rod memory

device (33); (189).

2. the cubic waffle-iron memory device (31)

.

7. Ni-Fe-Al Permalloy films containing aluminum were

mentioned (135) in a study into the origin

and control of the anisotropy in magnetic

thin films.

....

8a.80Ni-17Fe-3Co Under the proper deposition conditions,

this melt composition reportedly provides

a nonmagnetostrictive film with lower

easy-axis skew from element to element

than is the case with films of 81-permalloy

(29).

1. magnetic film store (190).

2. logic circuits (191).

40
Material Interesting Features Applications

8b.57Ni-13Fe-30Co Films made from this melt composition

feature zero magnetostriction, and provide

a reasonably large "nucleation factor" for

the shift register application.

-domain wall motion shift

regis terSc.48.6Ni-2.8Fe48.6Co

Films from this melt composition have

higher wall coercive force values (~10 oe.), and no magnetoelastic sensitivity.

-mentioned in studies to achieve

higher bit densities in magnetic

film memories, while maintaining

an open flux structure (37)

.

8d.45Ni-30Fe-25Co

(perminvars)

Perminvar characteristics are listed in the comments to Table I.

Ni-Fe-Co

(other)

The nonmagnetostrictive compositions in the Ni-Fe-Co system (see, e.g., ref. 34,

Fig. 4) may be of interest when higher

values of Hc , Hj^ are desired than are provided by the usual 81 -permalloy com- position. Some disagreement concerning

nonmagnetostrictive composition exists

at higher Cobalt contents —45 to 50% Co

(37).

-mentioned for use in a proposed memory element (146)

9. Ni-Fe-Cr In bulk, these alloys have been used where

it is desired to have magnetic properties

that change rapidly with change in temperature - e.g., temperature sensitive relays (1)

10.Ni-Fe-Cu Copper additions have a quenching action on

the magnetization of Ni-Fe films (148)

.

11.Ni-Fe-Mo The combination of low magnetostriction and anisotropy of 4-79 molybdenum permalloy at room temperature should make it a very

desirable film material (29)

.

reproduce head (200)

12.Ni-Fe-P These films were developed to lower the drive

current requirements of magnetic thin film

memories, thereby making the films more

compatible with molecular type integrated

circuits (41) . They provide rapid switching

and zero magnetostriction.

-proposed as the memory elements

in a low power, thin film memory (41), (154), (192).

41
Material Interesting Features Applications

13.Fe-Al These films were examined to 3tudy the

influence of directional ordering on their

anisotropy (135). Bulk samples of similar

compositions had previously displayed such

influence on their induced anisotropy (43)

(The uniaxial magnetic anisotropy of perm- alloy films near 80Ni-20Fe is thought to be

due in part to directional ordering of the

solute atoms as described by the NeelTaniguchi theory (83)

....

14a.50Fe-50Co This alloy composition features very high

saturation magnetization and high magnetostriction.

....

14b.5Fe-95Co .... -reportedly used in "Bicore",

a NDRO storage device (29)

14c.Fe-Co

(other)

Iron-cobalt alloys are of interest when

high Curie points (see, e.g., Ref. 194) or high values of saturation induction

are important. The alloy composition near

907. Co has low magnetostriction combined

with a higher coercive force than 81- permalloy.

A higher coercive force material

such as 90Co-10Fe was mentioned

for possible use as the analogue

storage element in a magnetic

film adaptive linear decision

array (193).

15.Ni-Cu

16.Ni-Pd

Nickel and copper are neighbors in the periodic table; one is ferromagnetic, and

the other is diamagnetic. Palladium, on

the other hand, lies directly below nickel

in the periodic table. Therefore, Ni-Cu

and Ni-Pd alloys may be interesting from a theoretical point of view.

Spin waves apparently can be excited

in thin nickel films only when stringent

conditions are met during the deposition

of the films; but, upon the addition of

small quantities of impurities, such as Cu

or Pd, the films produce spin wave spectra

(195).

• • • •

17.Ni-alloys

(other)

These alloys were used in special purpose

studies, etc.

• • • •

42
Material Interesting Features Applications

18.Co-Cu The successful production of metastable

Co-Cu alloy films, in the 40-85% Cu range, showed that metastable alloys never observed

in bulk materials may be produced as a thin

film by the simultaneous deposition of the various metals onto a cold substrate.

. • • •

19.Co-Ni The most commonly used magnetic recording

surfaces consist of either iron oxide

particles dispersed in a binder, or con- tinuous metallic films of cobalt and cobaltnickel (196) . These Co-Ni electrodeposits

generally have coercivities of 200-300 oe. when used in serial storage devices, although

a Co-Ni alloy having a coercive force of 500 oe. has been reported (51).

Electrodeposited Co-Ni alloys are widely used throughout the com- puter industry as the recording

media in magnetic drum and magnetic tape memory systems

(197).

20.Co-P Results taken from tape and drum testing

show improvements in recording properties

relative to magnetic oxide coatings (171)

.

These improvements correspond to those to be expected from thinner coatings having

higher coercive forces (171)

.

These high coercive force alloys

(200-700 oe.) may find use as the storage elements in drum,

disc, and tape units (48).

- potential use as a new magnetic tape medium (97)

.

21a.Co-Ni-P

(electroless)

Electroless Co-Ni-P films can have magnetic

properties that are similar to those of permalloy films (53)

.

-"orthocore" memory device (172)

.

-Co-Ni-P films formed by electroless deposition possess magnetic

properties that are potentially

useful as memory elements (53)

.

21b.Co-Ni-P

high coer- civity

electrodeposits

Electrodeposited Co-Ni-P films reported by

Bate and Speliotis (54) (55) (56) (58) (60)

show an unusual combination of magnetic

properties, including:

1. high coercivity.

2. high ratio of remanent to saturation

magnetization.

3. steep sided hysteresis loops.

4. magnetic isotropy in the film plane.

-high density recording on discs

and drums (e.g., see (48),

Fig. 7).-

43
Material Interesting Features Applications

22.Ferrite Films Optical studies of the ferrite material in thin film form may be possible, by trans- mission, even though the material is opaque

in bulk form.

1. potential applications in millimeter-microwave ferrite

devices, e.g., circulators,

masers, isolators, switches,

variable attenuators, etc. (65).

2. memory or logic elements (174).

3. thin film inductors (180).

23.Garnet Films Garnet materials, especially yttrium iron

garnet, are characterized by a relatively narrow ferromagnetic resonance line width.

This narrow line width is important in the design of practical devices (201).

Garnet in bulk may find use as delay lines at microwave

frequency (198). Other possibilities

include such microwave devices as switches, circulators, isolators,

etc.

44
Selected Bibliography

(1) R. Bozorth, Ferromagnetism - D. Van Nostrand Co. , Inc.

(1951)

(2) Handbook of Chemistry and Physics , 39th Edition; Chemical

Rubber Publishing Co. (1957)

(3) American Institute of Physics Handbook, Second Edition.

McGraw-Hill Book Co. , Inc. (1963)

(4) Y. Gondo et al, J. Appl. Phys. 34, 1081 (1963)

(5) E.E.Huber et al, J. Appl. Phys. 2_9, 294 (1958)

(6) E.L. Boyd, IBM J. Res. and Dev. , Vol. 4, No. 2; 116, (I960)

(7) A.Arrott and J. Goldman, "Fundamentals of Ferromagnetism"

The Gage Publishing Co. (1959)

(8) F. Seitz and D. Turnbull, Solid State Physics, Vol. 3;

Academic Press, Inc. N. Y^ (1956);

(Article by Kittel and Gait, pp 437 - 564)

(9) S.C.Abrahams et al, Phys. Rev. 127 , 2052 (1962)

10) J.F. Freedman, J. Appl. Phys. 33, 1148 (1962) (Supplement)

11) R. W. Hoffman and A. M. Eich - Conf. on Magnetism and

Magnetic Materials, Boston, Mass. , Oct. 16-18, 1956 - p 78

12) O.S. Heavens, Res. Appl. in Ind. _13, 404 (I960)

13) C. D. Graham and J. M. Lommel, J.Phys.Soc. Japan, Vol.17,

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54
\JJ*

PAGE INDEX

Magnetic Film Material

Cobalt, hep

Cobalt, fee

Cobalt -copper

Cobalt-nickel

Cobalt-nickel-phosphorus

Cobalt -phosphorus Ferrite

Gadolinium

Garnet

Iron, bec

Iron, fee

I ron- aluminum

Iron-cobalt

Iron-cobalt

Iron -cobalt

Iron-nickel (see nickeliron)

Miscellaneous

MnBi

Nickel, fee

Nickel, hep

Nickel-copper

Nickel ferrite

Nickel-iron

Nickel-iron

Nickel-iron

Nickel-iron-aluminum

Nickel-iron-cobalt

Nickel-iron-cobalt

Nickel-iron-cobalt

Nickel-iron-cobalt

Nickel-iron-cobalt

Nickel-iron-chromium

Nickel-iron-copper

Nickel-iron-molybdenum

Nickel -iron-phosphorus

Nickel- (other alloys)

Nickel-palladium

Permalloys (see nickeliron)

Permendur

Perminvar

YIG

Category Page

3a $, 13, 14, 39

3b 5, 13, 14, 24, 39

18 34, 43

19 9, 21, 34, 43

21a;21b 9, 21, 35, 43

20 9, 21, 35, 43

22 10, 22, 36, 44

4 6, 15, 25, 39

23 10, 22, 37, 44

la 5, 11, 39

lb 5, 12, 22, 39

13 8, 20, 32, 42

14a (50Fe -50Co) 8, 20, 32, 42

14b ( 5Fe -95Co) 8, 20, 32, 42

14c (other ) 21, 32, 42

24 37

5 6, 16, 26, 40

2a 5, 12, 39

2b 5, 13, 22, 39

15 8, 33, 42 ___ 10

6a (81Ni -19Fe) 6, 16, 40

6b(50Ni--50Fe) 6, 17, 27, 40

6c (3Ni-97Fe) 6, 17, 27, 40

7 6, 18, 27, 40

8a (80Ni- 7, 18, 28, 40

17Fe-3Co)

8b(57Ni- 7, 18, 28, 41

13Fe-30Co)

8c (48. 6Ni- 7, 18, 29, 41

2.8Fe -48.6Co) 8d (perminvar s) 7, 18, 29, 41

8e (other ) 18, 30, 41

9 7, 19, 30, 41

10 7, 30, 41

11 8, 19, 31, 41

12 8, 19, 31, 41

17 33, 42

16 9, 33, 42

14a 8, 20, 32, 42

8d 7, 18, 29, 41

EC

10, 44

GPO 881-303




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