Journal of Magnetism and Magnetic Materials 260 (2003) 406–414

Enhanced magnetic properties of Nd–Fe–B thin ﬁlms
crystallized by heat treatment
L.K.E.B. Serronaa,*,1, R. Fujisakia, A. Sugimuraa, T. Okudaa, N. Adachia,
H. Ohsatoa, I. Sakamotoa, A. Nakanishib,2, M. Motokawac, D.H. Pingd, K. Honoda

Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 Japanb
Sumitomo Special Metals Co., Shimamoto-cho, Osaka 618-0013 Japanc
Institute for Materials Research, Tohuku University, Sendai 980-8577 Japand
National Institute for Materials Science, Sengen, Tsukuba 305-0047, Japan
Received 20 August 2002

Abstract
Nd2Fe14B F phase crystallites were formed in Nd16.7Fe65.5B17.8 thin ﬁlms prepared by RF sputtering with subsequent
heat treatment. The 2 mm-thick ﬁlms were deposited onto 0.1 mm Mo sheets at an average substrate temperature ðTs Þ of3651C. The enhanced magnetic properties of the magnetically anisotropic thin ﬁlms were investigated using different
heating rates ðhr Þ of 101C, 201C, 501C and 1001C/min in an annealing experiment. Transformation from the amorphous
phase to the crystalline phase is clearly manifested by the formation of ﬁne crystallites embedded as a columnar matrixof Nd2Fe14B phase. High-resolution scanning electron microscope data of the cross-section of the annealed ﬁlms show
columnar stacking of Nd2Fe14B crystallites with sizes o500 nm. Transmission electron microscope observations
revealed that the microstructure of these ﬁlms having out-of-plane magnetization consists of uniformly distributed F
phase with grain size around 400 nm together with small Nd rich particles. This grain size of F phase is comparable tothe single domain particle diameter of Nd2Fe14B. Signiﬁcant change in i Hc ; 4pMr> and 4pMs> with hr was conﬁrmed.
Annealing conditions with a heating rate of 501C/min to an annealing temperature ðTa Þ of 6501C for 30 min wasconsequently found to give optimum properties for the NdFeB thin ﬁlms. The resulting magnetic properties, considered
to be the effect of varying hr were i Hc = 1307–1357 kA/m, 4pMr> =0.78–1.06 T and 4pMs> =0.81–1.07 T.
r 2002 Elsevier Science B.V. All rights reserved.
Keywords: Nd2Fe14B; Thin ﬁlms; High coercivity; Thermal annealing; Microstructure; Heating rate; Hard magnetic materials

1. Introduction*Corresponding author. Tel.: +81-52-735-5290; fax: +8152-735-5294.
E-mail address: leokebs@hotmail.com (L.K.E.B. Serrona).
1
On leave from the Department of MSE, University of thePhilippines-Diliman, Diliman, Quezon City 1101, Philippines.
2
Present Address: Takuma National College of Technology,
Takuma-cho, Mitoyo-gun, Kagawa 769-1192, Japan.

NdFeB permanent magnet thin ﬁlms are ideal
for micro-motors, micro-actuators [1], microelectromechanical systems [2], magnetic sensors,etc., due to its remarkable room temperature
intrinsic properties, which include high magnetization and high magneto-crystalline anisotropy [3].

0304-8853/03/$ - see front matter r 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 3 0 4 - 8 8 5 3 ( 0 2 ) 0 1 3 8 0 - X

L.K.E.B. Serrona et al. / Journal of Magnetism and Magnetic Materials 260 (2003) 406–414

These magnetic properties when associated with
textured NdFeB F phase crystallites with the caxis preferentially aligned along the ﬁlm normal,
an excellent material for permanent magnet thinﬁlm applications can be realized. Reasonably, amajor concern in the preparation of Nd2Fe14B
materials in nanocrystalline form is to takeadvantage of the high magnetocrystalline anisotropy of NdFeB F phase achieved when an
optimal nanocrystalline structure is formed. Recently, our experiments yielded signiﬁcant resultsin the fabrication of these magnetic thin ﬁlms by
sputtering the amorphous ﬁlms onto Mo substrates with subsequent vacuum annealing tocrystallize the ﬁlms. We were able to optimize
some important parameters like target composition which would give higher coercivity andvacuum annealing conditions such as temperatureand time for crystallization [4,5]. In anotherrelated experiment, the use of glass insulation
between the substrate and the water-cooled substrate holder made it possible to keep the surface
temperature of the substrate during deposition at a
certain range below the crystallization temperatureand far above room temperature [6]. Amorphousﬁlms deposited in HTD conditions (glass-insulated
Mo substrates) exhibited weak perpendicularanisotropy that were deemed necessary for the
self-texturing mechanism in the F phase crystallites in annealed ﬁlms. On the contrary, one
deposited in LTD conditions (no glass insulation)
exhibited typical soft magnetic properties with inplane anisotropy. Investigating further on postannealing conditions, it was found that aside fromusing the initial heating rate (hr ) of 101C/min
whichproducedanisotropic
ﬁlms
with
H
B1290
kA/m
[6],
higherhinvacuumanneali cr
ing was also effective in producing enhanced
magnetic properties.
Using a lamp heating type vacuum furnace, theexperiment was conducted based on the rapid
thermal annealing (RTA) techniques that involves
a time–temperature proﬁle characterized by quick
heating (high ramp rate) and very short annealing
time. The RTA method has been reported to be
essential in the fabrication of isotropic nanostructured NdFeB ﬁlms with high Hc and high ðMr =Ms Þratio [7]. In addition, according to experimental

407

results in nanocomposite magnets, rapid annealingenhances the homogeneity of the magnetic phases
thus increasing the exchange-coupled regions
between the interacting grains [8]. We annealed
the ﬁlms for 30 min and a maximum hr of 1001C/
min and these parameters are actually incomparable with the heating rate of 2001C/s and 10 sannealing time for RTA. However, comparing ourannealing techniques with RTA procedures, there
exist certain similar effects particularly in thedevelopment of the microstructure corresponding
to enhanced magnetic properties.
Similar phenomena in melt quench ribbons were
found wherein direct quenching led to isotropic
crystal growth [9]. Whereas, we found out that ourthermal annealing procedure in Nd–Fe–B thinﬁlms prepared in HTD conditions resulted toanisotropic crystal growth. In both cases, highcoercivity is developed by the suppression of
crystal growth into appropriate grain size as aneffect of the different heat treatment parameters.
In melt quench ribbons, high magnetization is dueto the exchange coupling in the nanocrystals withgrains size much lesser than the single domain
particle diameter of 260 nm for Nd2Fe14B [10]. It isalso characterized by the homogeneous distribution of regularly shaped grains. On the other hand,
our work on Nd–Fe–B thin ﬁlms using typicalthermal annealing with an optimum heating rateof 501C/min and annealing at 6501C for 30 min led
to the development of high coercivity ﬁlms with
out-of-plane magnetization and columnar grain
structure observed in the ﬁlm cross-section. The
anisotropic crystal growth of F phase grains
resulted to nearly single domain size particles
having a texture with the c-axis preferentiallyoriented along the ﬁlm normal. High coercivity(i Hc ) and high remanent to saturation magnetization ratio (Mr =Ms ) were also found.
Present work was aimed to examine the effect ofincreasing the initial heating rate of vacuum
thermal annealing on the microstructural andmagnetic properties in the thin ﬁlm samples. In
this paper, we will report on the development ofdesirable hard magnetic properties from ﬁlm
samples which are amorphous as deposited andwere subsequently crystallized based on optimum
parameters of a post annealing method.

L.K.E.B. Serrona et al. / Journal of Magnetism and Magnetic Materials 260 (2003) 406–414

408

2. Experimental procedure

Annealing Temp. (°C)

The NdFeB ﬁlms were deposited using a
conventional RF sputtering device with a
100 mm diameter cast Nd20Fe64B16 target [4]added with a (1.5 cm)2 Fe sheet. The working
distance between substrate and target is 50 mm.
The sputtering chamber was evacuated to a
background pressure of about 2.7  104 Pa andthen Ar gas was introduced into the chamber andall deposition was made at a constant totalpressure of 6.7  101 Pa. The ﬁlms were depositedon ultrasonically pre-cleaned and chemicallyetched 0.1 mm thick as-rolled Mo sheets. The Mo
substrates were thermally insulated by 1 mm glass
sheet from a water-cooled copper substrate holder.
The details about the use of glass insulation
beneath the substrates in this experiment isreported elsewhere [6]. The junction of thealumel–chromel thermocouple was inserted between the substrate and glass insulation formonitoring the temperature of the substrate in
the entire deposition process. The ﬁlms were(
deposited for 1 h at a rate of around 260 A/min
with an RF power=350 W. No in situ heating andbiasing magnetic ﬁeld were employed. After ﬁlm( wasdeposition, a thin coating of Ti around 700 A
deposited for 5 min at 350 W to protect the ﬁlm
surface from oxidation. Annealing, shown schematically in Fig. 1 was done in vacuum using an
infrared image-furnace. In previous reports, thetypical conditions for initial heating rate (hr ),maximum temperature ðTa Þ and holding time ðta Þ
Initial heating rates:
1 100°C/min
3 20°C/min
4 10°C/min
2 50°C/min
30 min, 650° C, 6.7 × 10 -4 Pa
1

2 3

4

Furnace Cooling to R.T.

Annealing Time (min)Fig. 1. Schematic representation of the annealing procedureused in the experiment.

were 101C/min, 6501C and 30 min, respectively.
The specimens were furnace-cooled to room
temperature. These were experimentally optimized
for the ﬁlms prepared using Nd20Fe64B16 target [6].
To determine the optimum initial heating rate (hr )that will supposedly correspond to high i Hc ;4pMr> and 4pMs> values, a series of annealing
experiments were performed using hr =101C, 201C,
501C and 1001C/min. DEKTAK proﬁle meter wasused to measure the thickness of the ﬁlm samples.
SQUID Measurements and X-ray diffraction
techniques were used to characterize the magnetic
and structural properties of the crystalline ﬁlms,
respectively. Cross-section morphologies and planar grain sizes were examined by high-resolution
SEM and TEM, respectively. The composition of
the ﬁlms was analyzed by inductively coupledplasma (ICP) method.

3. Results and discussion
3.1. XRD patterns
During RF sputter deposition of the ﬁlm in the
HTD conditions, the substrate temperature changed from 3501C to 3731C. The average temperature for the entire deposition is 3651C. As can beseen in Fig. 2, the as deposited ﬁlm is amorphouswith a diffraction peak identiﬁed as Ti (0 0.2) andtwo other peaks indexed as Mo(1 1 0) andMo(2 0 0). Heating rate (hr ) dependence of the Xray diffraction patterns for the annealed ﬁlms
measured with Cu Ka radiation is also presented inFig. 2. The phase identiﬁcation and determinationof crystallographic parameters were based on thetetragonal Nd2Fe14B (JCPDS 39-0473) data. It is
obvious that the c-axis is strongly oriented
perpendicular to the ﬁlm plane because the 002c
peaks such as the 004, 006 and 008 reﬂections of
the F phase have considerably high intensity. In
addition to the 110 and 200 diffraction peaks of
Mo substrates, there are two unknown small peaks
and Nd oxide diffraction peaks observed at
2y=30.41 and 53.51. Other F phase peaks like
214, 115, 225, 208 and 218 are also observed but
their intensities are very weak. The XRD patterns
show no extra phase developed during annealingL.K.E.B. Serrona et al. / Journal of Magnetism and Magnetic Materials 260 (2003) 406–414

409

Intensity Ratio (I006/I214)

18
16
14
12
10
8
6
20

60
40
80
ο
Heating Rate ( C/min)

100

Fig. 3. Relative intensity ratio of ðI006 =I214 Þ as a function of theinitial heating rates during annealing.

Fig. 2. X-ray diffraction patterns of as-deposited ﬁlm andannealed ﬁlms plotted in increasing order of the initial heating
rates (hr ).

and represents diffraction planes that tend toorient the crystals away from the normal to theﬁlm plane direction. For the isotropic NdFeB
powder material, I006 =I214 ratio is around 0.28 [12].
Fig. 3 depicts the proﬁle of the intensity ratios andinitial heating rates having a maximum value at
hr =501C/min and a minimum value at hr =101C/
min. Higher values for the I006 =I214 intensity ratio
indicate that the ﬁlm samples possess considerable
degree of orientation perpendicular to the ﬁlm
plane. The identical proﬁles of the hr andmagnetization curves in Figs. 3 and 5, respectively,
proves existence of the inﬂuence of hr on the
texturing of the ﬁlms. The close relationshipbetween texture and 4pM> can therefore be
established.
3.2. Magnetic hysteresis loops

using hr up to 1001C/min. This kind of texturing
has been consistently considered in previous
experiments to be an indication of remarkableorientation of c-axis perpendicular to the ﬁlm
plane [11].
A plot of the intensity ratio between the strong
diffraction line 006 and 214 ðI006 =I214 Þ and hr ismade to compare the perpendicular orientation of
the crystalline phases. The 214 diffraction index
was chosen because it has the strongest intensity
among the powder diffraction peaks from F phase

Shown in Fig. 4(a) and (b) are the hysteresis
loops measured with ﬁeld applied up to 5600 kA/min the directions perpendicular (H>) and parallel(H8) to the ﬁlm plane using SQUID magnetometer. For the ﬁlms measured with H>, higher caxis texturing are indicated by higher 4pMr> and4pMs> values. The hysteresis loops of the ﬁlms
reveal a common single magnetic phase characteristics although there are secondary phases present.
According to the results summarized in Fig. 5, theL.K.E.B. Serrona et al. / Journal of Magnetism and Magnetic Materials 260 (2003) 406–414

410

H ⊥ plane

0

Heating rate
( ° C/min)
10
20
50
100

-0.5
-1.0

(a)

-1.6
0
1.6 3.2
Applied Field (MA/m)

Magnetization (T)Magnetization (T)0.5-4.8 -3.2

H // plane

1.0

1.0

0.5
0

Heating rate
( ° C/min)
10
20
50
100

-0.5
-1.0
-4.8

4.8
(b)

-3.2

-1.6
0 1.6 3.2
Applied Field (MA/m)

4.8

Fig. 4. Hysteresis loops of ﬁlms annealed using different initial heating rates. (a) Applied ﬁeld is normal to the ﬁlm surface. Correction
for demagnetization was made. (b) Applied ﬁeld is along the ﬁlm plane.

H ⊥ planeΟ

Coercivity (iHc) kA/m

1360

1.2
i Hc

4πMs ⊥
4πMr ⊥

1344

1.1
1.0

1328
0.9
1312
0.8

1296
1280

4πMr⊥ and 4πMs⊥ (T)

1376

0.7
0

20

40
60
80
Heating Rate (°C/min)

100

Fig. 5. Dependence of the intrinsic coercivity (i Hc ), remanent(4pMr> ) and saturation magnetization (4pMs> ) on the initialheating rates (hr ).

optimum initial heating rate is around 501C/min
higher than the usual 101C/min used in previous
experiments [6,11]. The 4pMr> and 4pMs> of the
ﬁlm annealed using hr =501C/min is higher thanthose ﬁlms annealed using hr =101C, 201C and1001C/min. Samples annealed using either lower hr(10oC/min and 201C/min) or higher hr (1001C/min) than the optimum is characterized by low
coercivity and low magnetization. The small but
noticeable changes in i Hc values are indications of

the existence of minor changes in size and shape ofF phase crystallites. Although there is no important change in the coercivity mechanism, it isobvious that c-axis texturing of the ﬁlms affected
the i Hc values. Signiﬁcant results can also be foundin the high squareness of the loops, which is nearly
unity (B1).
Magnetic properties measured with H8, out-ofplane magnetization behavior is observed. Smallbends near H=0 kA/m are present except for thecondition where hr =501C/min. These are causedby the presence of small quantities of soft magnetic
phases with in-plane anisotropy and these wereactually undetectable by conventional X-ray measurements. It can also be observed that hysteresis
loops appear long and narrow with an obvious
change in its inclinations towards saturation as hr
is varied. The changes in the slopes can be
regarded as an effect of the different texture in
the ﬁlms.
The hysteresis loops measured with H> and H8
illustrate that the F phase crystallites formed in theannealed ﬁlms indicate that the c-axis is parallel tothe ﬁlm normal and randomly oriented along theﬁlm plane after a magnetic ﬁeld was applied
perpendicular and parallel to the ﬁlm surface,respectively. The combined high magnetocrystalline anisotropy and high saturation magnetization

L.K.E.B. Serrona et al. / Journal of Magnetism and Magnetic Materials 260 (2003) 406–414

411

in the Nd2Fe14B phase contributed to the development of the anisotropic behavior in the ﬁlms.
Enhanced magnetic properties resulted from themicrostructural transformations during annealingthat were affected by the changes in the initialheating rates directly related to the extent of thenucleation and crystallization process.
3.3. SEM micrographs
Fig. 6 shows the SEM micrographs of the crosssection of amorphous and annealed Nd–Fe–B thinﬁlms using two different hr of 101C and 501C/min.
Amorphous ﬁlms surface are mirror-like and thecross-section surface are dense and continuous andno voids are found as shown in Fig. 6(a).
Subsequent annealing transforms the ﬁlms into astack of microcrystalline grains with diameterso500 nm in a columnar structure together withsome voids considered to be a source of theanisotropic character which in turn inﬂuences themagnetic anisotropy in this ﬁlms [13]. The crystallites are arranged along a direction perpendicular
to the ﬁlm surface closely associated with thedirection of the growth of the ﬁlm during
sputtering deposition. Micrographs in Fig. 6(b)and (c) correspond to an assembly of small
crystallites less than a micron size comprising the
microscopic texture of the permanent magnet
material. However, intrinsic magnetic properties
are actually dependent on size of the individual
grains and the presence of appropriate grainboundary phases [14].
The micrograph for hr =101C/min reveals that
this ﬁlm consists of Nd2Fe14B nanocrystallites lessthan 0.5 mm in diameter. The cross-section ischaracterized by some regularly spaced blocks aswell as voids formed in a columnar-like structure.
At this heating rate, ﬁlms produced have lesser
coercivity and remanent magnetization comparedto the ﬁlms annealed at hr =201C and 501C/min.
At an optimum hr =501C/min, the ﬁlm crosssection is characterized by the presence of more
ﬁner crystals with diameters less than 0.3 mm.
These ﬁne crystals together with some small voids
surround the large and elongated 0.5 mm crystallites. Enhanced magnetic properties were found in
this sample with i Hc =1357 kA/m, 4pMr> = 1.06 T

Fig. 6. Cross-sectional SEM micrographs showing the morphology of NdFeB ﬁlms at (a) as-deposited state, (b) hr =101C/
min and (c) hr =501C/min.

412

L.K.E.B. Serrona et al. / Journal of Magnetism and Magnetic Materials 260 (2003) 406–414

Fig. 7. Planar TEM images of annealed ﬁlms (6501C, 30 min) with hr 101C/min and; (b) 501C/min. Small arrow points to the location
and Nd rich particles (white and dark spots).

and 4pMs> =1.07 T. Distinct cross-sectional microstructure can be observed from the two
micrographs with hr of 101C and 501C/min. Thiscan be due to the effect of different crystallization
behavior brought about by the use of different hr :It can also be seen that the columnar alignmentand homogeneous distribution of the crystallites
can be understood to be a source of the highcoercivity and anisotropic behavior inherent in theﬁlms.
3.4. TEM micrographs
The microstructure of this off-stoichiometricNd16.7Fe65.5B17.8 thin ﬁlm consists of large andequiaxed grains having the hard magnetic phasesurrounded by minor Nd rich particles. Fig. 7(a)and (b) show the bright ﬁeld TEM images of theﬁlms annealed at 6501C for 30 min using hr =101C
and 501C/min, respectively. From the micrographs, Nd rich particles and other small precipitates (indicated by small arrows) are present in
the grain boundaries and there are few particles
found inside the grains. The grain size for thishighly anisotropic Nd–Fe–B thin ﬁlm material
estimated from the micrographs is around 400 nm.

This grain size is much greater than the single
domain size of B160 nm of melt spun ribbons [15]with nearly the same coercive force and Curie
temperature. Critical single domain particle diameters for Nd2Fe14B of 300 and 400 nm wereactually reported earlier by Herbst et.al. [16] andLivingston, [17] respectively. However, recent
studies reported grain sizes around 50 nm or lesscorresponding to enhanced magnetic properties
for both isotropic and anisotropic Nd–Fe–B
nanocrystalline materials [14]. In the case of highly
coercive and anisotropic sputtered ﬁlms, Kapitanov et.al. [18] reported grain sizes o600 nm. Theyobserved Nd–Fe–B grain structures with small
inclusions in and out of the individual grains. The
initial magnetization curve of the ﬁlm annealed
using hr =101C/min behaved like typical nucleation type permanent magnet [11]. Therefore, it isreasonable to consider that the grains observed in
our annealed ﬁlm can be regarded as single
domain particles.
Slow initial heating rate at 101C/min favors
growth of other minority phases including
some voids that would lead to the formationof inhomogeneous microstructure. It can beobserved from Fig. 7(a) that the irregular form

L.K.E.B. Serrona et al. / Journal of Magnetism and Magnetic Materials 260 (2003) 406–414

and distribution of the grains maybe a consequenceof prolonged initial heating. Corresponding i Hc and4pMr> for this sample is 1309 kA/m and 0.78 T,
respectively. On the other hand, for hr =501C/min,well-deﬁned grain patterns are observable inFig. 7(b) with few smaller particles inside andaround the Nd2Fe14B grains. The quick increasein heating suppressed the growth of various
intergranular phases giving way to the Nd2Fe14B
phase to form a ﬁne-grained microstructure. Forintermediate and higher hr at 201C and 1001C/min,
respectively, the effects were not remarkable to gain
consideration because experimental results showed
inadequate description for the comparison of themagnetic and structural properties.
Even though it is shown in Fig. 4(a) that thesquareness ratio of all the loops is nearly unity(B1) after correction of the demagnetizing ﬁeld,
there exist some remarkable changes in 4pMr>
and 4pMs> values as shown in Fig. 5. Identicalﬁlm samples were previously reported to containsingle magnetic phase [6] and in this recent
investigation, magnetic property changes were
found to be associated with the formation anddistribution of Nd2Fe14B grains as shown in
Fig. 7(a) and (b). From Fig. 7(a), non-uniform
grains structure formed using hr =101C/min resulted to an entirely weaker exchange interaction
between neighboring Nd2Fe14B nanocrystallites
suggesting lower magnetization. Examining theresults for hr =501C/min shown in Fig. 7(b), a
stronger exchange coupling among the nanocrystallites are to be expected because of the formationof a ﬁne-grained structure. In that case, increased
exchange interaction between the magnetic grains
resulted to higher magnetization [19].

413

vacuum at 6501C for 30 min. All the ﬁlm samples
show remarkable structural and magnetic properties in its crystalline form after annealing using
different hr of 101C, 201C, 501C and 1001C/min.
Two distinct results between using 10 and 501C/
min heating rates showed formation of Nd2Fe14B
nanocrystals in the columnar cross-section of the
ﬁlm with diameters o0.5 mm and o0.3 mm,
respectively. The increase of i Hc and 4pMr> to1357 kA/m and 1.06 T, respectively, made it
possible for the thin ﬁlm sample to attainremarkable magnetic properties at an hr of 501C/
min. The Nd2Fe14B grain size after subsequentannealing is estimated to be about 400 nm from
TEM observations. Crystallization at higher initialheating rates produced higher density of nucleithat resulted to ﬁner microstructure and suppressed formation of possible low temperaturephases. The resulting nanocrystalline structure
showed some indication in the magnetic propertiesof exchange interaction between the magnetic
moments of the Nd2Fe14B individual grains. These
are believed to have contributed to the high i Hc ;4pMr> and 4pMs> values. It can be summarized
therefore, that the enhancement of remanence
accompanied by the increase in coercivity is
obtained from crystallizing amorphous ﬁlms
into nearly single domain Nd2Fe14B nanocrystallites characterized by a c-axis oriented textured
structure developed normal to the ﬁlm plane.
These results are very important for the understanding of high coercivity mechanism and thenfor the selection of the best possible microstructural characteristic to be controlled in order tofurther improve the magnetic properties of the
ﬁlms.

4. Conclusions
Acknowledgements
The synthesis of anisotropic and high coercivity
NdFeB thin ﬁlms by post annealing of as RFsputter-deposited ﬁlms has been discussed withemphasis on the enhancement of magnetic properties due to the optimized initial heating rate in thethermal annealing experiment. The ﬁlms depositedat an average substrate temperature of 3651C were
amorphous and were subsequently annealed in

The authors are thankful to Dr. T. Hihara of the
Nagoya Institute of Technology (NIT) and Mr. M.
Sakai of the Okazaki National Research Institutefor the SQUID measurements and to Prof. T.
Kasuga (NIT) for the Scanning Electron
Microscopy observations. L.K.E.B. Serrona
gratefully acknowledges of the support of414

L.K.E.B. Serrona et al. / Journal of Magnetism and Magnetic Materials 260 (2003) 406–414

the Japanese Government Monbu-kagakusho
scholarship.

References[1] S. Yamashita, J. Yamasaki, M. Ikeda, N. Iwabuchi, J.
Appl. Phys. 70 (1991) 6627;.
H. Lemke, T. Lang, T. Goddenhenrich,
C. Heiden, J.
Magn. Magn. Mater. 148 (1995) 426.
[2] T.S. Chin, J. Magn. Magn. Mater. 209 (2000) 75.
[3] R.A. McCurrie, Ferromagnetic Materials: Structure andProperties, Academic Press Ltd., London, 1994.
[4] A. Nakanishi, M. Ueda, T. Okuda, N. Mizutani, J.
Nishiyama, M. Motokawa, Z. Wang, N. Adachi, H.
Ohsato, J. Magn. Magn. Mater. 196–197 (1999) 295.
[5] N. Mizutani, T. Okuda, A. Nakanishi, J. Nishiyama, M.
Motokawa, Z. Wang, N. Adachi, H. Ohsato, J. Magn.
Soc. Japan 297 (1999) 23.
[6] L.K.E.B. Serrona, A. Sugimura, R. Fujisaki, T. Okuda, N.
Adachi, H. Ohsato, I. Sakamoto, A. Nakanishi, M.
Motokawa, Trans. Magn. Soc. Japan 2 (2002) 93.
[7] M. Yu, Y. Liu, S.H. Liou, D.J. Sellmyer, J. Appl. Phys. 83(1998) 6611.
[8] A. Kojima, A. Makino, A. Inoue, J. Appl. Phys. 87 (2000) 6576.

[9] L. Withanawasam, G.C. Hadjipanayis, R.F. Krause, J.
Appl. Phys. 75 (1994) 6646.
[10] D. Jiles, Introduction to Magnetism and Magnetic
Materials, Chapman and Hall, New York, 1991.
[11] K. Terazawa, L. Serrona, T. Okuda, N. Adachi, I.
Sakamoto, A. Nakanishi, in: H. Kaneko, M. Homma,
M. Okada (Eds.), Proceedings of the 16th International
Workshop on Rare Earth Magnets and Their Applications, Sendai, 2000, pp. 393-402 (The Japan Institute of
Metals, Japan, 2000).
[12] Powder Diffraction File, JCPDS ICDD, PA, USA,1989.
[13] J.A. Thornton, J. Vac. Sci. Technol. A 4 (1986) 63059.
[14] G.C. Hadjipanayis, J. Magn. Magn. Mater. 200 (1999)
373.
[15] J.J. Croat, J.F. Herbst, R.W. Lee, F.E. Pinkerton, J. Appl.
Phys. 55 (1984) 2078.
[16] J.F. Herbst, Rev. Mod. Phys. 63 (1991) 819.
[17] J.D. Livingston, Proceedings of the 8th International
Workshop on Rare-Earth Magnets and their Applications,
Dayton, OH, 1985.
[18] B.A. Kapitanov, N.V. Kornilov, Ya.L. Linetsky, V.Yu.
Tsvetkov, J. Magn. Magn. Mater. 127 (1993) 289.
.
[19] M. Dahlgren, R. Grosingger,
in: F.P. Missel (Ed.),
Materials Science Forum, Vols. 302–303, Trans Tech
Publications, Switzerland, 1999, p. 263.