Magnetic transducer head

A magnetic transducer head wherein confronting surfaces of a pair of magnetic core parts comprised of a ferromagnetic oxide material are notched, and the notch defining surfaces have metallic ferromagnetic layers supported thereby. The method of physical vapor deposition as known per se is used for forming these layers. The transducer coupling gap of each magnetic head is defined by an aligned pair of pole piece layers formed from the deposited metallic ferromagnetic material. The pole piece layers are inclined at a preset angle with respect to the plane of the coupling gap, and have extensions formed of the deposited metallic ferromagnetic material presenting bend contours between the pole piece layers and the lateral sides of the core parts.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a magnetic transducer head and, more 
particularly, to a composite type magnetic transducer head wherein the gap 
defining region of the head is formed of thin layers of metallic magnetic 
material. 
2. Description of the Prior Art 
In magnetic recording and/or reproducing apparatus, such as video tape 
recorders (VTRs), the recent tendency has been toward increasing the 
signal density of the recording medium. In order to increase the recorded 
signal density, so-called metal powder tapes and so-called metallized 
magnetic tapes with high coercive force (H.sub.c) are being used in 
increasing numbers. The metal powder tapes make use of powders of 
ferromagnetic metals such as iron, cobalt or nickel, or alloys thereof, 
while the so-called metallized tapes utilize a ferromagnetic metallic 
material coated on a film substrate by means of vapor deposition. Because 
of the high coercivity of these types of magnetic recording media, a high 
saturation magnetic flux density (B.sub.s) is required of the magnetic 
core material of the magnetic transducer head, particularly for a head 
utilized for signal recording operation. With the ferrite magnetic 
material predominantly used in magnetic recording, the saturation magnetic 
flux density is rather low, while a metallic magnetic material such as 
Permalloy presents a problem in that it has a lower wear resistance. 
With the above-described tendency toward increasing the recorded signal 
density, it is desirable to make use of a narrow record track width on the 
magnetic recording medium, and for this purpose, it is necessary to have a 
magnetic transducer head coupling gap with a corresponding narrow lateral 
dimension. 
In seeking to meet such requirements, a composite type magnetic transducer 
head has been previously developed in which a ferromagnetic metallic layer 
is deposited on a non-magnetic substrate, for example, of a ceramic 
material, with the thickness of the deposited layer corresponding to the 
record track width. This type of magnetic transducer head, however, 
presents a high magnetic reluctance for high frequency signal components 
because the entire magnetic signal flux path in the head is formed by the 
low resistivity ferromagnetic metallic layer. Furthermore, since the 
metallic magnetic layer is produced by physical vapor deposition with its 
characteristic slow deposition rate, the requirement that the thickness of 
the deposited layers must equal the track width can lead to a relatively 
long processing time and consequent materially increased production cost. 
A composite type magnetic transducer head is also known in the art in which 
magnetic core elements are formed of ferromagnetic oxides such as ferrite, 
and ferromagnetic metallic layers are applied to confronting surfaces of 
the core elements for defining the transducer gap. However, in this case 
the path of magnetic flux and the broad surfaces of the metallic magnetic 
layers are disposed at right angles to each other, and playback output may 
be lowered because of the resulting eddy current loss. Also, a pseudo gap 
is produced at the interface between each of the ferrite magnetic core 
elements add the associated metallic magnetic layer, with a resulting 
detriment to a desired uniformity of playback frequency response. 
RELATED PATENT APPLICATIONS 
The following commonly owned pending applications are specifically 
incorporated herein by reference: 
(1) Kobayashi et al application "Magnetic Transducer Head", U.S. Ser. No. 
686,540 filed Dec. 26, 1984; and 
(2) Kubota et al application "Magnetic Transducer Head", U.S. Ser. No. 
713,637 filed Mar. 19, 1985. 
The above-mentioned U.S. application Ser. No. 686,540 discloses magnetic 
heads of a composite type suitable for high density recording on high 
coercivity magnetic record tapes such as the so-called metal powder tapes 
and metallized magnetic tapes previously referred to. An example of such a 
head is shown in FIG. 20 of the accompanying drawings wherein a pair of 
magnetic core elements 101 and 102 of ferrite material have obliquely 
disposed surfaces 103, 104 on which layers 105, 106 of a metallic magnetic 
material such as Sendust are deposited by a physical vapor deposition 
process. The layers 105 and 106 are aligned so that edge faces of the 
layers define a transducer gap 107 corresponding to a record track width 
greater than the thickness of the deposited layers. The frontal portions 
of the ferrite magnetic core elements 101 and 102 are separated from each 
other at each side of the gap region 107 by non-magnetic filling material 
108, 109, 110 and 111. The non-magnetic material 108, 109 extends in flush 
supporting relationship with record tape engaging edge faces of the 
deposited layers 105 and 106 so as to protect the deposited layers from 
wear. The non-magnetic material at 108-111 results in a shape of the 
magnetic structure of the transducer head in conformity with the desired 
record track width. By way of example, the material at 108 and 109 in FIG. 
20 may be a glass material having a relatively low melting temperature, 
while the material at 110 and 111 may be a glass material having a 
relatively high melting temperature. The magnetic head of FIG. 20 exhibits 
superior characteristics in operational reliability, magnetic performance 
and wear resistance in comparison to prior art heads. 
In the manufacture of the magnetic head of FIG. 20, a pair of core blocks 
are prepared such that a plurality of individual transducer head chips can 
be sliced from the core blocks after they have been united in a proper 
registering relationship. As may be seen from FIG. 20, the composite core 
parts which include the respective ferrite core elements 101 and 102 may 
be formed from identically processed core blocks, except that one of the 
core blocks will receive a groove for forming the winding aperture 112 of 
the finished core assembly. In an exemplary sequence of manufacturing 
steps, a ferrite substrate may first receive a series of parallel V-shaped 
grooves which are then filled with glass of a relatively high melting 
temperature, such glass ultimately providing the non-magnetic filling 
material 110, 111 for each individual finished head. As a next step, 
further V-shaped grooves may be formed between the previously formed 
grooves. A side wall of each of the further grooves will ultimately 
correspond with an obliquely disposed surface such as 103 or 104 of a 
finished transducer head core assembly such as shown in FIG. 20. As a next 
step in the manufacturing process, the surface formed by each ferrite 
substrate and its glass-filled first grooves and the further open grooves 
may now receive a deposited layer of a suitable metallic magnetic material 
such as Sendust. The open grooves with the deposited layers therein may 
receive a glass of low melting temperature which eventually provides 
non-magnetic glass material as shown at 108 and 109 in FIG. 20. The excess 
of the deposited metallic magnetic material is removed and the resulting 
surface is polished to a mirror finish to define a planar mating surface. 
The planar mating surfaces of two such core blocks are placed in 
confronting relation with a gap spacer material therebetween, and the two 
core blocks are united to form an assembly which is then sliced along 
parallel cutting planes to form a plurality of individual head chips. 
Referring to the individual transducer head chip of FIG. 20, the slicing 
operation at the parallel cutting planes produces lateral sides 114 and 
115. 
A magnetic head such as illustrated in FIG. 20 is still not optimum in that 
lateral edge portions 105a and 106a of the deposited metallic magnetic 
layers 105 and 106 are cut during the slicing operation in such a way as 
to detrimentally affect the magnetic properties of the layers 105 and 106. 
In particular, the magnetic reluctance of the essential magnetic signal 
flux paths in the layers 105 and 106 is increased, and the useful 
recording magnetic flux density produced at the gap 107 is reduced during 
recording operation, and the sensitivity of the transducer head during 
playback operation is also reduced. It is considered that this detrimental 
increase in magnetic reluctance of the essential magnetic signal flux 
paths is caused by differential thermal expansion between the ferrite 
surfaces such as 103 and 104 and the deposited layers such as 105 and 106 
of metallic magnetic material. In particular, it is considered that the 
mechanical stress caused by the differential thermal expansion leads to 
the formation of cracks in the deposited layers such as 105 and 106, with 
a resulting disruption of the uniform magnetic characteristics of the 
layers as intially formed. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to overcome the 
above-mentioned difficulties in relation to the metallic magnetic layers 
which define the gap region of composite magnetic transducer heads, such 
that the portions of the deposited metallic magnetic layers forming 
essential parts of the transducer head magnetic signal flux path are 
substantially free of detrimental thermally induced stress. 
It is a further object of the present invention to provide a method of 
manufacturing composite magnetic transducer heads which produces heads 
with improved uniformity of magnetic characteristics and operational 
reliability; a related object is to provide a composite magnetic 
transducer head of essentially optimum magnetic characteristics which may 
be manufactured in an efficient and economical manner, and wherein the 
portions of deposited metallic magnetic layers essential to the magnetic 
signal flux path (hereafter termed the magnetic pole piece layers) are 
isolated from detrimental stress caused by differential thermal expansion 
at the time of slicing individual transducer head chips from mating and 
registered core blocks. 
It is another object of the present invention to provide a method of mass 
production of composite magnetic transducer heads wherein the yield rate 
of magnetic transducer heads with superior magnetic characteristics is 
notably improved. 
In a preferred method implementation of the present invention, core blocks 
comprised of ferromagnetic oxide material are placed in mating 
relationship, with obliquely disposed pole piece layers of deposited 
metallic magnetic material in alignment across an interface region between 
the confronting core blocks. As viewed in a frontal plane of the core 
block assembly, the grooves receiving the pole piece layers present notch 
configurations with first notch defining surfaces which support the pole 
piece layers, extending obliquely from the respective confronting 
surfaces. Because of the contour of the grooves, further notch defining 
surfaces which form continuations of the first notch defining surfaces 
include bend contours and lateral extensions disposed laterally outwardly 
of the pole piece layers. By slicing the core block assembly outwardly of 
the bend contours, the pole piece layers are shielded from thermal stress 
resulting from the cutting forces. To limit the record tape contacting 
surface to a desired width, the notch configurations may receive chamfers 
so that only the pole piece layers have edge faces at the level of the 
record tape contacting surface and so that the lateral extensions are 
removed from such surface. 
In a preferred magnetic transducer head as produced in accordance with the 
foregoing method, a composite magnetic core as sliced from a core block 
assembly has lateral sides which are spaced laterally outwardly from the 
pole piece layers so that the pole piece layers are essentially free from 
the thermal stress which has been found to be detrimental in transducer 
heads such as shown in FIG. 20. Where an optimum magnetic transducer head 
has pole piece layers forming a straight line completely across the record 
tape contacting surface, detrimental thermal stress may be avoided by 
slicing the transducer head chip with an overall lateral dimension greater 
than the desired width of the record tape contacting surface, and removing 
unwanted extensions (which extend laterally from the pole piece layers), 
for example by forming chamfers at the lateral sides of the transducer 
head. Most preferably, the magnetic transducer head chips are sliced from 
a composite core block assembly along cutting planes extending laterally 
outwardly of bend contours which then shield the pole piece layers from 
detrimental thermal stress due to the cutting forces, so that a stable and 
highly reliable transducer head is obtained even on a mass production 
basis. 
In a modification, the extensions from the pole piece layers may extend 
generally away from the interface plane as well as laterally and be of a 
curved contour and of reduced thickness to isolate the pole piece layers 
from thermal stress. Further, the cutting planes may be laterally 
outwardly of respective relatively sharp bend contours in such extensions 
and intersect lateral extremities of the deposited layers which are 
relatively thin and extend from the sharp bend contours generally toward 
the interface plane. The lateral extremities may be removed from the tape 
contacting surface by chamfering. 
Other objects, features and advantages of the present disclosure will be 
apparent from the following detailed description taken in connection with 
the accompanying sheets of drawings, from the objects and features of the 
incorporated disclosures, and from the claims appended to the respective 
disclosures. It is specifically contemplated that the inventive entity 
named herein may be enlarged to encompass all such objects, features and 
advantages.

Exemplary preferred magnetic transducer heads and methods in accordance 
with the present disclosure will now be explained in the following 
detailed description which refers to FIGS. 1-19 of the accompanying 
drawings. 
DESCRIPTION OF PREFERRED EMBODIMENTS 
In FIG. 1, there is shown in perspective an example of a composite magnetic 
head embodying the preferred inventive improvements of the present 
disclosure. The reference numerals I and II designate respective composite 
core parts which have been united in a prior processing step and then 
severed along cutting planes parallel to the broad lateral sides of the 
core parts to form an individual core assembly such as shown in FIG. 1. 
The core part I comprises a magnetic core element 1 having a frontal 
portion 1A and a main body portion 1B. The cooperating core part II 
comprises a magnetic core element 2 having a frontal portion 2A and a main 
body portion 2B. The magnetic core element 2 is shown as containing a 
winding slot 2C so that an electric coil can be formed about the signal 
magnetic flux path provided by the magnetic core element 2. 
In FIG. 2, frontal surface portions IA and IIA of the composite core parts 
I and II are shown in an enlarged plan view restricted to the gap region. 
In FIG. 2, the width of the main body portions 1B and 2B is designated by 
the letter W. By way of example, magnetic core elements 1 and 2 may be 
formed of a ferromagnetic oxide material such as manganese-zinc ferrite. 
As viewed in FIG. 2, the composite core parts present respective notch 
configurations 3 and 4 which contain respective layers 5 and 6 of metallic 
magnetic material. The layers 5 and 6 include aligned parts 5A and 6A, 
herein termed the magnetic pole piece layers, which include record tape 
engaging edge faces 5a and 6a, FIG. 2, and which provide essential 
portions of the magnetic recording signal flux path of the transducer 
head. The pole piece layers 5A and 6A extend in close conforming relation 
to obliquely disposed portions 7A and 8A of notch defining surfaces 7 and 
8. In one embodiment, the layers 5 and 6 are formed by depositing metallic 
magnetic material on the notch defining surfaces 7 and 8 by a vapor 
deposition process. 
As illustrated in FIG. 2, the surfaces 7A and 8A each form an angle with an 
interface plane which coincides with an interface region 9 between the 
composite core parts I and II. The pole piece layers 5A and 6A are shown 
as having a substantially uniform thickness t. The pole piece layers 5A 
and 6A have confronting edge faces lying at opposite sides of the 
interface region 9 and defining therebetween a transducer coupling gap 10 
for coupling the magnetic transducer head with a track of a magnetic tape 
record medium, the lateral extent of the gap 10 essentially defining a 
track width dimension Tw which may be taken as representing the record 
track width which is to be scanned by the transducer head during recording 
and/or playback. 
As viewed in FIG. 2, the composite core parts exhibit recess configurations 
11 and 12, and the layers 5 and 6 are shown as defining further recess 
configurations. The recess configurations associated with layers 5 and 6 
are filled with non-magnetic material as indicated at 13 and 14 while the 
recess configurations 11 and 12 contain non-magnetic material as indicated 
at 15 and 16. By way of example, a glass of relatively high melting 
temperature may serve as non-magnetic materials 13 and 14, while a glass 
with a relatively lower melting temperature can be utilized for the 
non-magnetic materials 15 and 16. 
The interface region 9 may be formed by a gap material such as silicon 
dioxide (SiO.sub.2) which is applied to one or both of the mating surfaces 
of the composite core parts I and II. The angle .theta. between the 
respective obliquely disposed surfaces 7A and 8A which support the pole 
piece layers 5A and 6A, and the plane of interface region 9 is preferably 
in the range from twenty degrees to eighty degrees. With angle .theta. 
less than twenty degrees, cross-talk from the neighboring tracks is 
increased, and accordingly the angle .theta. is preferably selected to be 
larger than thirty degrees. The angle .theta. is also selected to be less 
than about eighty degrees because wear resistance is severely reduced as 
the angle .theta. approaches ninety degrees. With the angle .theta. equal 
to ninety degrees, the deposited metallic magnetic layers 5 and 6 must 
have a thickness equal to the track width Tw. This is not desirable 
because the operation of depositing a layer with the aid of a physical 
vapor deposition is extremely time consuming; further, as the thickness of 
the layer increases, the structure of the layer becomes less uniform, and 
the magnetic properties of the transducer head are correspondingly 
degraded. 
Referring to the geometry illustrated in FIG. 2, it will be observed that 
the thickness t of the deposited pole piece layers 5A and 6A is less than 
the track width according to the relationship: 
EQU t=Tw sin .theta. 
where Tw designates the track width and .theta. is the angle between the 
respective obliquely disposed surfaces 7A and 8A and the plane of the 
interface region 9. Accordingly, by appropriate selection of the angle 
.theta., the film thickness t may be reduced in comparison with the track 
width Tw so that the time involved in the manufacture of the magnetic head 
may be correspondingly reduced. 
The materials of the metallic magnetic layers 5 and 6 may include 
non-crystalline ferromagnetic metallic alloys, i.e. so-called amorphous 
alloys, for example metal-metalloid amorphous alloys, such as alloys 
composed of one or more metals from a group comprised of iron (Fe), nickel 
(Ni) and cobalt (Co), and one or more elements from a group comprised of 
phosphorous (P), carbon (C), boron (B), and silicon (Si), or alloys mainly 
consisting of elements from these groups and also including aluminum (Al), 
germanium (Ge), beryllium (Be), tin (Sn), indium (In), molybdenum (Mo), 
tungsten (W), titanium (Ti), manganese (Mn), chromium (Cr), zirconium 
(Zr), hafnium (Hf) or niobium (Nb), or metal-metal amorphous alloys mainly 
consisting of cobalt (Co), hafnium (Hf) or zirconium (Zr); 
iron-aluminum-silicon alloys (Sendust alloys); iron-aluminum alloys; and 
nickeliron alloys (Permalloys). Deposition of the desired layers herein 
can be achieved by any conventional method of physical vapor deposition, 
such as flash evaporation, gas evaporation, ion plating, sputtering and 
cluster ion beam deposition. 
The recess configurations of the transducer head which contain the 
non-magnetic materials 13, 14, 15 and 16 shape the magnetic structure of 
the head so as to concentrate the signal magnetic flux at the region of 
gap 10 while providing a transducer head tape contacting surface of great 
stability and wear resistance. 
As viewed in FIG. 2, the deposited metallic magnetic layers 5 and 6 have a 
generally V-shaped configuration, with the pole piece layers 5A and 6A 
joined with lateral extremities 5B and 6B of substantially reduced 
thickness by means of respective bends 5C and 6C. The lateral extremities 
of the deposited layers at 5B and 6B are spaced in a depth direction from 
the level of the tape contact surface of the head as best seen in FIG. 1 
for the case of extremity 6B. Referring to FIG. 1, it will be observed 
that the main regions 5A and 6A of the layers 5 and 6 extend from a level 
flush with the transducer head tape contacting surface to a substantial 
depth corresponding to the depth dimension of the transducer gap 10. In 
the embodiment of FIGS. 1 and 2, the offsetting or removal of the layer 
portion 5B, 5C and 6B, 6C from the level of the transducer head tape 
contacting surface is effected by chamfering the composite core parts I 
and II to form L-shaped steps 17 and 18 as best seen in FIG. 1. 
As will be explained hereinafter with reference to FIGS. 8 and 9, the 
lateral dimension D which is shown in FIG. 2 and represents the overall 
lateral span of the pair of juxtaposed notch configurations 3 and 4 is 
selected in this embodiment so as to be smaller than the thickness W of 
the main body portions 1B and 2B of the transducer head. In this way, when 
a pair of mated and registered core blocks are sliced to form individual 
magnetic head chips such as shown in FIGS. 1 and 2, cutting takes place in 
laterally spaced relationship to the pair of aligned pole piece layers 5A 
and 6A so that these layers are isolated from the thermal stress caused by 
the cutting operation. As a result, the pole piece layers 5A and 6A retain 
their original magnetic properties and in particular the formation of 
cracks in the layers 5A and 6A which would be detrimental to the magnetic 
properties are avoided. 
With the above-described magnetic head, the lateral extremities 5B and 6B 
of the deposited layers of metallic magnetic material extend from the 
bends 5C, 6C in a direction generally toward the interface region 9 as 
seen in FIG. 2. If such lateral extremities 5B and 6B were located at the 
transducer head tape contacting surface, so-called pseudo magnetic gaps 
would be formed; however, according to the present embodiment, the 
surfaces 17a, 18a containing the lateral extremities 5B and 6B and the 
adjoining lateral margin portions of the core elements 1 and 2 are offset 
from the level of the tape contacting surface, so that only the desired 
transducer gap 10 defined by the pole piece layers 5A and 6B is present at 
the tape contacting surface. 
The following description of a preferred method of manufacture of the 
magnetic transducer head of FIGS. 1 and 2 will serve to provide a further 
understanding of the structure of this embodiment. 
In the method step illustrated in FIG. 3, a plurality of spaced vee grooves 
21 are formed with a grinding wheel assembly (not shown) which groves open 
at an upper surface 20a of a substrate 20 and provide obliquely disposed 
surfaces such as indicated at 21a. The surface 20a may be regarded as a 
mating or confronting surface since two such surfaces of respective 
similar substrates after further processing are mated in confronting 
relation as shown in FIG. 8. The mating surface 20a is parallel with the 
interface plane of the head assemblies which are ultimately formed. The 
obliquely disposed surfaces 21a are inclined at the selected angle .theta. 
(FIG. 2) with respect to the plane of surface 20a. In the present 
embodiment, the angle .theta. is selected to be about forty-five degrees. 
As illustrated in FIG. 4, a metallic magnetic layer 23 of Sendust or the 
like is applied to the grooved side of substrate 20 so as to a form layer 
portions 23A with a layer thickness t on the obliquely disposed surfaces 
such as 21a in FIG. 3. The layer 23 at its exterior (upper) side provides 
surface portions parallel to the surface 20a and recesses 24 generally 
conforming with the contour of the original grooves 21. The layer 23 may 
have a reduced thickness at portions such as 23A, FIG. 4, which are 
deposited at the sides 21b of the grooves 21, corresponding to the reduced 
thickness of the individual layers such as 5 and 6 of FIG. 2 at the 
respective extremities 5B and 6B in FIG. 2. Where the layer 23 is formed 
by physical vapor deposition, for example by sputtering, the substrate 20 
may be held at such an angle to the sputtering apparatus that material is 
preferentially deposited at the respective oblique surfaces such as 21a, 
while the desired reduced thickness of deposited material is produced at 
the surfaces 21b of the vee grooves 21. 
As shown in FIG. 5, the recesses 24, FIG. 4, may now be filled with 
non-magnetic material 25, such as glass with a high melting temperature. 
The surface with layer 23 thereon, FIG. 4, is now ground smooth so that 
the edge portions such as 23a and 23b of the deposited metallic magnetic 
layer 23 are flush with the substrate surface 20a to provide an 
essentially continuous smooth flat planar surface over the entire grooved 
side of the substrate 20. 
Then, as shown in FIG. 6, a second set of grooves 27 is milled parallel 
with the original vee grooves 21, FIG. 3, with each of the grooves 27 
closely approaching an edge portion 23a of a respective deposited pole 
piece layer 23A (this step providing the recesses such as indicated at 11 
and 12 in FIG. 2 which extend into close proximity to the margins of the 
gap 10). The mating surface 20a of the substrate and the coplanar surfaces 
23a and 23b of layer 23 and coplanar surfaces 25a of the non-magnetic 
material 25 are then ground to a mirror finish. The grooves 27 may 
slightly overlap with the adjacent margins of the pole piece layer edge 
faces 23a, eliminating the presence of magnetic substrate material at the 
lateral extremities of the transducer head coupling gaps corresponding to 
gap 10 in FIG. 2. The combined lateral extent of the grooves 21 and 27 
corresponds to the dimension D in FIG. 2 and in this embodiment is 
selected so as to be smaller than the slicing width represented at M in 
FIG. 8 and substantially corresponding with the width W shown in FIG. 2. 
The second grooves 27, FIG. 6, may, for example, be polygonal in 
cross-section so that the inner wall surface of each slot 27 is bent in 
two or more steps, with surfaces such as indicated at 27a adjoining the 
pole piece layers 23A having a desirable relatively steep angle relative 
to the plane of surface 20a, FIG. 6. The contour of the slots 27 is 
selected for assuring a desired distance between the magnetic oxide 
material, for example, of core element 1, FIG. 2, and the metallic 
magnetic layer such as 6A, FIG. 2. The profile of the grooves 27 is 
selected to reduce cross-talk components at the longer recorded 
wavelengths during playback operation. The magnetic oxide material of the 
core elements 1 and 2 supports the pole piece layers 5A and 6A, FIG. 2, in 
close conforming relation over the entire extent of the pole piece layers 
5A and 6A at the tape contacting surface and over a depth dimension 
corresponding to the depth dimension of the gap 10, the depth dimension of 
the gap 10 being limited by the presence of the slot 2C in the core 
element 2B, FIG. 1. The profile of the slots 27, FIG. 6, also allows the 
confronting faces of the magnetic oxide material of the core elements 1 
and 2 to be inclined relative to the plane of gap 10 to avoid spurious 
recording in the scanning direction of the head while also reducing 
crosstalk or signal pickup from adjacent, and next adjacent, tracks during 
playback operation. Pickup from adjacent tracks, for example, is inhibited 
because of the azimuth loss introduced as a result of the oblique angle of 
surfaces such as indicated at 1a and 2a in FIG. 2 which result from the 
contour of grooves 27 at 27a and 27b, FIG. 6, for example. 
FIG. 7 shows a core block comprising of a second substrate 30 processed as 
shown in FIGS. 3 through 6, but thereafter having a groove 29 formed in a 
direction at right angles to grooves 21' and 27' which correspond to the 
grooves 21 and 27 of substrate 20. The groove 29 provides the winding 
slots such as indicated at 2C in FIG. 1 for the respective individual core 
assemblies to be formed. The substrate comprises deposited layers 33 of 
metallic magnetic material providing pole piece layers 33A with pole piece 
edge faces 33a. The core block including substrate 30 is provided with a 
grooved side including surface 30a, having a mirror finish so as to 
provide a flat planar surface for mating with the flat planar surface 
including the surface 20a of FIG. 6. FIG. 7 shows a total span of a groove 
21' and an adjoining groove 27' of Dw which corresponds to the dimension D 
in FIG. 2. A gap spacer material is deposited on the polished mating 
surface including the surface 20a of the substrate 20, FIG. 6, and/or on 
the polished surface which includes the surface 30a of the substrate 30, 
FIG. 7, so that the aligned layer edges 23a and 33a will have gap material 
therebetween establishing the desired longitudinal gap dimension 
therebetween. Then, as shown in FIG. 8, the core blocks comprised of 
substrate 20, FIG. 6, and substrate 30, FIG. 7, are mated and registered 
relative to one another so that respective pairs of deposited pole piece 
layers 23A and 33A are in alignment with each other as shown in FIG. 8 to 
define transducer gaps corresponding to the gap 10 of FIG. 2. The core 
blocks comprised of the processed substrates 20 and 30 are bonded together 
by glass, and the grooves 27 and 27' are filled with respective 
non-magnetic glass material 28 and 28'. The gap material for forming the 
interface regions such as 9, FIG. 2, and for providing the transducer gaps 
such as 10 may be selected from a group comprised of silicon dioxide 
(SiO.sub.2), zirconium dioxide (ZrO.sub.2), tantallum pentoxide (Ta.sub.2 
O.sub.5) and chromium (Cr). 
The mating core blocks formed by the processed substrates 20 and 30 are 
then sliced along lines such as A--A and A'--A' in FIG. 8 having a 
separation M, FIG. 8, which is greater than the dimension Dw, FIG. 7, and 
greater than the dimension D of FIG. 2. The result is a plurality of head 
chips such as indicated in FIG. 9, each such chip or core assembly having 
lateral sides such as indicated at 38 and 39 which are flat and planar and 
disposed at right angles to the interface plane between the core parts, 
such lateral sides 38 and 39 of the transducer head defining a width W 
such that the sides 38 and 39 are spaced laterally outwardly from the 
extremeties 5B and 6B of the layers 5 and 6. With this arrangement, the 
essential flux path defining portions 5A and 6A of the metallic magnetic 
layers 5 and 6 are thermally isolated from the lateral sides 38 and 39 so 
as to be free of detrimental thermal stress resulting from the cutting 
forces applied at the cutting planes A--A and A'--A' during severing of 
the core parts from the mated core blocks of FIG. 8. Accordingly, it is 
found that the layers 5A and 6A retain the desirable uniform magnetic 
properties that the layers had in their condition as shown in FIGS. 6 and 
7 prior to the slicing operation of FIG. 8. 
As illustrated in FIG. 9, an individual head chip 40 such as is obtained as 
indicated in FIG. 8, comprises a portion 20A of the substrate 20, FIG. 8, 
and a portion 30A of the substrate 30, FIG. 8. In order to form the 
transducer head record tape contacting surface from the core material at 
40a, the material at 40b and 40c laterally outwardly of the lines C--C and 
C'--C' in FIG. 9 are ground off in a chamfering operation, and the 
remaining surface of portion 40a, FIG. 9, is ground to a segmental 
cylindrical configuration for completing the magnetic head such as shown 
in FIGS. 1 and 2. By chamfering the longitudinal edges 40b and 40c, FIG. 
9, the pseudo gaps otherwise formed at margins 40b and 40c, FIG. 9, are 
separated from the level of the tape contact surface formed at the central 
portion 40a, FIG. 9. The longitudinal edges 40b and 40c may be chamfered 
to form beveled surfaces instead of the stepped surfaces as indicated at 
17 and 18 in FIG. 1. 
In the above described manufacturing process, it is not essential that the 
glass material 28 and 28' be charged into the respective second grooves 27 
and 27' of FIGS. 6 and 7 at the same time that the core blocks formed by 
the processed substrates 20 and 30 are bonded to each other. For example, 
the processing operations of FIGS. 6 and 7 may include the step of 
charging the glass material 28 and 28' into the second grooves 27 and 27', 
whereas the step of FIG. 8 may include only the glass bonding step where 
the core blocks are bonded together as a unitary assembly. 
The preferred embodiments of the present invention are not limited to the 
above described embodiment. For example, as shown in FIG. 10, the width of 
the juxtaposed notch configurations 3 and 4, and also the overall lateral 
span of the recess configurations 11 and 12 may be selected to have a 
value (indicated at D in FIG. 10) so as to be slightly larger than the 
width W of the magnetic core body portions 1B and 2B. In this example the 
cutting planes intersect lateral extremities 5B and 6B of the deposited 
metallic magnetic material which lateral extremities lie laterally 
outwardly of the bends 5C and 6C (as viewed in relation to the associated 
transducer gap 10). The thickness of the deposited metallic magnetic 
material is substantially less in these lateral extremities 5B and 6B so 
that a disruption due to the thermal stress of the cutting operation is 
less likely to be transmitted to the magnetic pole piece layers 5A and 6A. 
Generally in each of the preferred embodiments, the thinner the deposited 
metallic magnetic material at the lateral extremeties, the less likely it 
is that thermal stress will be transmitted to the pole piece layers in the 
vicinity of the transducer gap 10. It is noted that the longitudinal edge 
portions 41b and 41c of the core parts which lie outside of the lines E--E 
and E'--E' are chamfered for removing them from the record tape contacting 
surface which is provided at a central region 41a corresponding to the 
regions IA and IIA of FIG. 1. 
As a further modification, as shown in FIG. 11, the juxtaposed notch 
configurations 3 and 4 may be of a sinuous profile at the extensions 3B 
and 4B of the first notch defining surfaces 3A and 4A. In this example, 
the deposited metallic magnetic material of layers 5 and 6 may be formed 
with substantially conforming S-shaped bends including relatively sharp 
reverse bends at 5D and 6D, with regions 5E and 6E being of progressively 
reduced thickness and curving generally away from the interface plane, and 
being located between the pole piece layers 5A and 6A and the relatively 
sharp bends 5D and 6D, and with lateral extremities 5F and 6F being of 
substantially reduced thickness and extending from the relatively sharp 
bends 5D and 6D in a direction generally toward the interface plane as 
well as generally laterally outwardly. In the illustrated example, the 
cutting planes intersect the lateral extremities 5F and 6F which lie 
laterally outside of the sharp bends 5D and 6D to form the lateral sides 
43 and 44 of the individual transducer head chip. As in the preceeding 
embodiment of FIG. 10, there is no risk of detrimental disruption of the 
deposited pole piece layers 5A and 6A in the vicinity of the transducer 
gap 10 or crack formation in the closely conforming notch defining 
surfaces 3A and 4A of magnetic oxide material. Thus, in the embodiments of 
FIG. 10 and FIG. 11, the pole piece layers 5A and 6A are essentially free 
of detrimental thermal stress which might lead to detrimental cracks in 
the pole piece layers. In FIG. 11, the lateral margin portions 42b and 42c 
outside of the lines F--F and F' --F' are removed by chamfering in 
correspondence with the embodiment shown in FIG. 1. Thus, the sharp bends 
5D and 6D and the lateral extremities 5F and 6F are removed from the 
record tape contacting surface formed at 42a. 
As a modification, the metallic magnetic layers may be provided solely in 
the vicinity of the coupling gap of the magnetic transducer head. 
FIG. 12 shows a modified magnetic transducer head wherein the metallic 
magnetic layers are provided solely in the vicinity of the coupling gap. 
The magnetic head is comprised of a pair of core elements 51 and 52 of a 
ferromagnetic oxide material such as manganese-zinc ferrite, and it is 
only on frontal portions of the core parts in the vicinity of the magnetic 
gap g that the metallic magnetic layers 54 of a high permeability alloy 
such as Sendust are deposited by a vacuum film formation technique such as 
sputtering. Reference numerals 55 and 56 designate non-magnetic filling 
material, for example glass filling material, charged in a molten state 
into recess configurations disposed at the respective lateral margins of 
the gap g. As in the preceding preferred embodiments, pole piece layers 
54A forming essential portions of the magnetic flux path of the head are 
of substantially uniform magnetic characteristics, and are essentially 
free of detrimental thermal stress so as to provide a magnetic transducer 
head with optimum, extremely stable magnetic properties and capable of 
reliable operation over an extended useful life. 
In the embodiment of FIG. 12, longitudinal edge portions 57 and 58 on both 
sides of the record contacting surface 59 are obliquely removed by a 
chamfering operation. 
The magnetic transducer head of FIG. 12 may be prepared by the steps shown 
in FIGS. 13 to 19. 
Referring first to FIG. 13, with the aid of a grinding wheel or 
electro-etching, a plurality of equally spaced dihedral grooves 61 are 
formed at a transverse edge of a substrate 60 of a ferromagnetic oxide 
material such as manganese-zinc ferrite. The upper surface 60a as viewed 
in FIG. 13 of the substrate 60 forms part of the mating surface of a core 
block as in the preceding example. However, the grooves 61 are formed at 
only a portion of the surface 60a which will correspond to the vicinity of 
the transducer head coupling gaps of the individual magnetic transducer 
head chips which are to be formed from a pair of such core blocks. 
As shown in FIG. 14, glass material 62 is filled in a molten state in each 
groove 61, and the surfaces such as 62a and 62b are then ground smooth to 
provide a planar mating surface and a planar frontal surface of the core 
block. 
As shown in FIG. 15, a plurality of second grooves 65 are formed so as to 
be adjacent to and partially overlapped with the grooves 61 which are 
filled with the glass material 62. In forming the grooves 65, a part 62c 
of the glass material 62 is exposed to form part of a notch defining 
surface along with the groove wall 65a of each groove 65. Each of the 
resultant notch defining surfaces 67 intersects the plane of the upper 
surface 60a along a line 66 which extends at right angles to a frontal 
plane defined by front surface 60b of the substrate 60. Each of the notch 
defining surfaces 67 forms a preselected angle, for example of forty-five 
degrees, with the plane defined by the upper surface 60a. The combined 
width of each pair of adjoining grooves 61 and 65, as viewed in the 
frontal plane defined by front surface 60b of the substrate may be 
selected so as to be slightly smaller than the width (corresponding to the 
dimension W, FIG. 2) of each head chip obtained after the slicing step as 
later described. 
Then, with the aid of a physical vapor deposition process, such as 
sputtering, a metallic magnetic material, for example a high permeability 
alloy such as Sendust, is deposited as a thin layer 68, as shown in FIG. 
16, which covers at least the second grooves 65 to leave residual recesses 
65', FIG. 16. In this process step, the substrate 60, FIG. 15, is placed 
in a sputtering unit in an inclined position for more efficient deposition 
of the high permeability alloy material on the notch defining surfaces 
such as indicated at 67 in FIG. 15. Thus, the deposited layer is of 
substantially reduced thickness at the lateral extremities such as 54B, 
FIG. 12, in comparison to the thickness at the pole piece layers such as 
54A, FIG. 12, in the resultant individual transducer head chips. 
Then, as shown in FIG. 17, a glass material 69 which has a lower melting 
temperature than the previously applied glass material 62 is charged in a 
molten state into the recesses 65' defined by the second grooves 65 with 
their lining of deposited metallic magnetic material 68, FIG. 16. The core 
block sides including upper surface 60a and the front surface 60b are then 
ground to a mirror finish. At this time, part of the deposited metallic 
magnetic material 68 remains in the second grooves 65 so that, when 
looking at the frontal plane of the core block defined by front side 60b 
of the substrate 60, vee layer configurations comprising layer segments 
68A and 68B remain deposited on the walls of the second grooves 65. 
For providing core parts with winding slots, a second core block, similar 
to that including the magnetic oxide substrate 60, FIG. 17, is subjected 
as a further step to the forming of a winding groove 71, FIG. 18. The 
result is a second core block including a substrate 70 of ferromagnetic 
oxide material providing a planar mating surface including surface 70a, 
FIG. 18. 
The mating surfaces of the core blocks formed of the processed substrates 
60 and 70 are superimposed upon each other as shown in FIG. 19 with the 
mating surfaces including surfaces 60a and 70a disposed in confronting 
relation and separated only by a deposited gap spacer material as in the 
preceding embodiment. The core blocks including the substrates 60 and 70 
are then bonded to each other by molten glass. The resulting unitary core 
block assembly comprised of the substrates 60 and 70 is sliced along lines 
such as G--G and G'--G' in FIG. 19 to form a plurality of individual 
transducer head chips. 
The record tape contacting surface of each resulting transducer head chip 
is ground to a segmental cylindrical surface such as indicated at 59, FIG. 
12, while the longitudinal edges of the chip on both sides of the tape 
contacting surface 59 are ground off to provide chamfered or beveled 
lateral margins 57 and 58 for completing the magnetic head as shown in 
FIG. 12. 
The magnetic head of FIG. 12 as prepared by the method steps of FIGS. 13 
through 19 is of a superior character because it is capable of high yield 
mass production and because there is no risk of formation of detrimental 
cracks in the pole piece layers such as 54A or in the notch defining 
surfaces 78 and 79, as has already been explained in reference to the 
preceding preferred embodiments. Furthermore, the embodiment of FIGS. 
12-19 substantially reduces the required volume of high permeability alloy 
by restricting the deposition process to the region of the transducer gaps 
of each head chip. The required amount of glass or other non-magnetic 
material is also substantially reduced in comparison to the embodiment of 
FIGS. 1 through 9. The heads of FIGS. 10 and 11 may be prepared by the 
method of FIGS. 3 through 9 or by the method of FIGS. 13 through 19. 
For each of the preferred magnetic head configurations described herein, 
the pole piece layers of deposited metallic magnetic material extend 
obliquely to the interface plane in the vicinity of the coupling gap and 
form a selected acute angle of substantial magnitude, for example in the 
range between about twenty degrees and about eighty degrees. In addition, 
the notch configurations provide relatively sharp bend contours between 
the pole piece layers and the lateral margins of the head so that the pole 
piece layers are essentially free of detrimental thermal stress and so 
that the formation of cracks in the pole piece layers or in the adjoining 
oxide ferromagnetic material as the result of slicing of the head chips 
from a core block assembly is notably reduced. Further, the preferred 
methods of the present disclosure enable the production of magnetic 
transducer heads with stable magnetic characteristics and with a long 
reliable operating life. Because of the shielding of the deposited 
magnetic pole piece layers from the thermal stress of the slicing 
operation, the danger of crack formation in the pole piece layers or in 
the supporting ferromagnetic oxide material is notably reduced so that the 
occurence of rejects is minimized. 
In addition, the volume of glass or like non-magnetic material to be 
charged into the track width controlling recess configurations is reduced 
because of the presence of the reverse bends in the notch configurations 
so that crack formation in this non-magnetic material, in the deposited 
pole piece layers or in the supporting magnetic oxide material may be 
prevented from occuring. 
While several preferred embodiments have been illustrated and described in 
detail, it will be apparent to those skilled in the art that many changes 
and modifications may be made without departing from the disclosed 
invention in its broader aspects; and it is intended that the appended 
claims cover all such changes and modifications as fall within the true 
spirit and scope of the contributions to the art made hereby.