In luence o mic os uc u e on he enhancemen o so magne ic cha ac e and he
induced aniso opy o ield annealed HITPERM- ype alloys
J. S. Blázquez, J. Ma cin, M. Va ga, V. F anco, A. Conde, and I. Sko anek
Ci a ion: Jou nal o Applied Physics 117, 17A301 (2015); doi: 10.1063/1.4906173
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In luence o mic os uc u e on he enhancemen o so magne ic cha ac e
and he induced aniso opy o ield annealed HITPERM- ype alloys
J. S. Bl
azquez,
1
J. Ma cin,
2
M. Va ga,
2
V. F anco,
1,a)
A. Conde,
1
and I. Sko anek
2
1
Depa amen o de F
ısica de la Ma e ia Condensada, ICM-SE CSIC, Uni e sidad de Se illa, P. O. Box 1065,
41080 Se illa, Spain
2
Ins i u e o Expe imen al Physics, Slo ak Academy o Sciences, SK-040 01 Kosice, Slo akia
(P esen ed 5 No embe 2014; ecei ed 4 Sep embe 2014; accep ed 15 Sep embe 2014; published
online 14 Janua y 2015)
Hi pe m- ype apidly quenched ibbons we e submi ed o ield annealing, bo h longi udinal ield
(LF) and ans e sal ield (TF) o he axis o he ibbon. LF annealing yields a educ ion o
he magne ic aniso opy and esul s can be explained in he ame o andom aniso opy model.
A coe ci i y o 3 A/m is ob ained o Fe
39
Co
39
Nb
6
B
15
Cu
1
alloy. The addi ion o Cu o hese
Nb-con aining Hi pe m- ype alloys is a key ac o o e ine he mic os uc u e in o de o each his
e y low coe ci i y alue. TF annealing p oduces samples wi h shea ed hys e esis loops sui able
o senso and high equency applica ions. V
C2015 AIP Publishing LLC.
[h p://dx.doi.o g/10.1063/1.4906173]
So magne ic nanoc ys alline alloys a e o med by e -
omagne ic a-Fe ype nanoc ys als embedded in a esidual
amo phous ma ix. As empe a u e inc eases abo e he Cu ie
empe a u e o he amo phous phase (T
C
Am
), he coupling
be ween nanoc ys als becomes de e io a ed and he ul aso
magne ic cha ac e o he sys em is los . In 1998, Hi pe m
alloys (Fe-Co-ETM-B-Cu being ETM ¼Z , Nb, Mo, H , e c.)
we e p oposed as so magne s o high empe a u e applica-
ions.
1
The key pa ame e o Hi pe m alloys is a high T
C
am
,
which gene ally exceeds he onse o nanoc ys alliza ion
empe a u e. The e o e, in o de o achie e he nanoc ys al-
line mic os uc u e, Hi pe m alloys ha e o be annealed
below T
C
am
implying a s abiliza ion o he magne ic domain
walls due o he pai o de ing mechanism.
2,3
In gene al, his
p ocedu e leads o a magne ic ha dening o he sys em.
4,5
Howe e , i has been shown ha ield annealing is e y
e ec i e o a oid his ha dening in Hi pe m alloys.
6–11
In
ac , as he sample is magne ically sa u a ed du ing he
annealing p ocess, s abiliza ion o domain walls is a oided
and coe ci i ies below 10 A/m a e ob ained o longi udinal
ield (LF) annealed Hi pe m alloys.
Amo phous ibbons (15 lm hick) o Fe
78x
Co
x
Nb
6
B
16y
Cu
y
(x ¼39, 60; y ¼0, 1) we e p oduced by mel -
spinning. Pieces 60 mm long, 5 mm wide, and 20 lm hick
we e annealed du ing 1 h a he peak empe a u e o he nano-
c ys alliza ion p ocess de ec ed by di e en ial scanning calo-
ime y (DSC) unde h ee di e en condi ions: (a) ze o
magne ic ield (ZF), (b) applying 20 kA/m LF, and (c) apply-
ing 640 kA/m ans e sal ield (TF) in he plane o he ibbon.
Hys e esis loops we e acqui ed using a Fo s e ype B-H loop
ace based on lux-ga e magne ome e .
In he Nb-con aining Hi pe m alloys wi h 39 a . % Co
con en , addi ion o 1 a . % Cu leads o a e inemen o he
mic os uc u e and he a e age c ys al size educes om
D¼7.5 nm o 5 nm a e Cu addi ion, whe eas c ys alline
ac ion a e he nanoc ys alliza ion emains una ec ed (X
C
55%). Howe e , o alloys wi h 60 a . % Co, c ys alline
ac ion dec eases (X
C
45%) due o exhaus ion o Fe in he
emaining amo phous ma ix and D¼5 nm.
12
FIG. 1. Hys e esis loops o AQ amo phous and annealed nanoc ys alline
samples o Fe
78x
Co
x
Nb
6
B
16y
Cu
y
alloys ((a) x ¼39 and y ¼1; (b) x ¼39
and y ¼0; (c) x ¼18 and y ¼1). Symbols a e plo ed each 25 da a poin s o
iden i y he cu es. A magni ied iew is shown in he inse s o app ecia e
he coe ci i y. Symbols in he inse co espond o indi idual (H) da a.
a)
Au ho o whom co espondence should be add essed. Elec onic mail:
[email p o ec ed].
0021-8979/2015/117(17)/17A301/3/$30.00 V
C2015 AIP Publishing LLC117, 17A301-1
JOURNAL OF APPLIED PHYSICS 117, 17A301 (2015)
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Figu e 1shows he hys e esis loops o nanoc ys alline
samples o he h ee s udied composi ions o ZF and LF
annealing along wi h he co esponding hys e esis loops o
he as-quenched (AQ) amo phous alloy. I can be obse ed
ha LF samples exhibi a squa e hys e esis loop and show a
clea so ening o he magne ic cha ac e wi h espec o ZF
annealed samples. A clea inc ease o sa u a ion magne iza-
ion (M
S
) is obse ed a e nanoc ys alliza ion due o he o -
ma ion o he a-FeCo phase. Howe e , ZF annealed samples
show a clea de e io a ion o he coe ci i y (H
C
) wi h espec
o AQ alloys due o he mechanism o pai o de ing. Low
coe ci i ies o AQ samples a e p ese ed o e en imp o ed
a e LF annealing (e.g., o x ¼39, y ¼1 alloy, H
C
¼3.1 A/
m compa ed o 9.8 A/m and 45 A/m o AQ and ZF
samples).
The mic os uc u al dependence o he obse ed mag-
ne ic da a can be analyzed in he amewo k o he andom
aniso opy model conside ing i s ex ension o wo-phase sys-
ems.
13,14
In his con ex , he magne oc ys alline aniso opy
a e ages ou due o he small size o he c ys alli es (smalle
han he exchange leng h) and i can be w i en as a unc ion
o he magne oc ys alline aniso opy, K
1
, he exchange s i -
ness, A, and he mic os uc u al pa ame e s Dand X
C
13
hKi¼ 3
4

3K4
1D6
A3XC2:(1)
This exp ession p edic s a dec ease o he a e age mag-
ne ic aniso opy, hKi, and hus o H
C
,asDdec eases, which
is in ag eemen wi h he obse ed di e ence be ween H
C
alues o 39 a . % Co alloys wi h and wi hou Cu. These
wo sys ems ha e he same olume ac ion and composi ion
o he c ys alline phase bu a la ge Dis obse ed o he Cu-
ee alloy. The change in he e ec i e magne ic aniso opy,
K
e
l
0
M
S
H
C
, can be compa ed o he expec ed change o
his a e aged aniso opy hKi. A simple calcula ion imposing
K
1
10 kJ/m
3
(Re . 15) o a Fe
0.61
Co
0.39
composi ion and
he mic os uc u al pa ame e s collec ed in Table Ileads o a
alue o A0.5 10
11
J/m, which is in good ag eemen
wi h he expec ed alue.
The wo s udied Cu-con aining alloys show D¼5nm. In
he case o he alloy wi h 60 a . % Co, a dec ease in X
C
wi h
espec o he alloy wi h 39 a . % Co alloys should imply a
dec ease in hKi o a cons an alue o D¼5 nm, in disag ee-
men wi h he obse ed end. The explana ion o his appa-
en con adic ion is he di e en composi ion o he
c ys alline phases, which yields di e en alues o K
1
.In ac ,
exp ession (1) shows a s onge dependence on K
1
han on X
C
.
The alue o K
1
depends on he composi ion o he a-FeCo
phase, being 50 kJ/m
3
o pu e a-Fe and dec easing as Co
con en inc eases down o 40 kJ/m
3
o 70 a . % Co.
15
The e o e, assuming ha he composi ions o nanoc ys als a e
Fe
0.61
Co
0.39
and Fe
0.4
Co
0.6
o he alloys wi h 39 and 60 a . %
Co, espec i ely,
16
K
1
can be es ima ed as þ10 kJ/m
3
and
20 kJ/m
3
o x ¼39 and 60 alloys, espec i ely,
15
which
explains he obse ed di e ence.
Figu e 2shows he hys e esis loops o TF annealed sam-
ples, which show shea ed loops, almos linea up o he ani-
so opy ield, H
k
, whe e M
S
is eached. This indica es ha
o a ion o magne ic momen s is he dominan mechanism
o magne iza ion in hese samples. Such ype o hys e esis
loops is especially in e es ing o senso applica ions,
TABLE I. Pa ame e s o nanoc ys alline samples ob ained a e annealing a T
a
.
Composi ion T
a
(K) D(nm) X
C
(%) C ys al phase composi ion K
1
(kJ/m
3
)q(g/cm
3
)
Fe
39
Co
39
Nb
6
B
15
Cu
1
739 5 55 Fe
0.61
Co
0.39
10 8.1
Fe
39
Co
39
Nb
6
B
16
766 7.5 55 Fe
0.61
Co
0.39
10 8.1
Fe
18
Co
60
Nb
6
B
15
Cu
1
736 5 45 Fe
0.4
Co
0.6
20 8.3
FIG. 2. Hys e esis loops o ans e sal ield annealed samples o he h ee
s udied composi ions.
FIG. 3. Sucksmi h-Thompson plo o he h ee s udied composi ions submi -
ed o ans e sal ield annealing. Lines co espond o linea i ings.
17A301-2 Bl
azquez e al. J. Appl. Phys. 117, 17A301 (2015)
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whe eas he educed suscep ibili y makes hese samples
in e es ing o high equency ans o me applica ions.
17
In o de o cha ac e ize he sensi i eness o TF anneal-
ing p ocess, he induced magne ic aniso opy, K
u
, has been
cha ac e ized using se e al p ocedu es. On he one hand, K
u
can be di ec ly es ima ed om he alue o he aniso opy
ield, H
k
, as: Ku¼l0MSHk=2, whe e H
k
has been es ima ed
as he linea ex apola ion o each M
S
.K
u
¼860, 1170, and
1090 J/m
3
o x ¼39, y ¼1; x ¼39, y ¼0, and x ¼18, y ¼1
alloys, espec i ely.
On he o he hand, he me hod o Sucksmi h and
Thompson
18
allows us o ob ain he wo i s coe icien s o
he magne ic aniso opy K
1u
and K
2u
based on he ela ion
2K1u
l0MS
ðÞ
2þ4K2u
l0MS
ðÞ
4l0MH
ðÞ

2¼H
l0MH
ðÞ
;(2)
whe e M(H) ep esen s he magne iza ion a a gi en ield H.
The e o e, ollowing exp ession (3), Figu e 3shows he plo
o H/(l
0
M) s(l
0
M)
2
om which K
1u
can be ob ained om
he alue o he in e cep wi h he y axis and K
2u
om
he slope o he cu e. The ob ained alues a e in ag eemen
wi h he p e ious ones. K
1u
¼849.0(5), 1182.5(6), and
1108.7(8) J/m
3
o x ¼39, y ¼1; x ¼39, y ¼0, and x ¼18,
y¼1 alloys, espec i ely.
Finally, a s udy on he dis ibu ion o aniso opy ields,
P(H
k
), can be done om he second de i a i e o he mag-
ne iza ion cu e using he wo b anches om sa u a ion o
emanence, as i has been desc ibed o amo phous
19
and
nanoc ys alline sys ems
20
PH
k
ðÞ¼
H
MS
d2MH
ðÞ
dH2:(3)
The co esponding plo s a e shown in Figu e 4. The e a e
no signi ican di e ences in he wid h o he dis ibu ion,
al hough i is smalle in he alloy wi h he highes Co con en .
I can be obse ed ha K
u
ollows he same end han he
esidual K
e
obse ed in LF annealed samples and desc ibed
abo e. The smalles alue o K
u
(o K
u1
) is ound o he alloy
wi h 39 a . % Co and 1 a . % Cu, whe eas he la ges alue o
induced aniso opy is ound o he Cu- ee alloy.
In conclusion, he magne ic ha dening obse ed in ZF
nanoc ys alline samples is p e en ed a e ield annealing
in he sa u a ion s a e and a minimum H
C
¼3A/mhas
been ob ained o LF which equal he bes H
C
alues
epo edup oda e o Fe
38
Co
38
Mo
8
B
15
Cu
1
Hi pe m
alloys.
8
Mic os uc u al and composi ional di e ences
be ween he s udied alloys can explain he di e ences
obse ed in hei magne ic p ope ies. On he o he hand,
whe eas LF yields a minimiza ion o hKiand squa e hys-
e esis loops, TF annealing p oduces samples wi h shea ed
hys e esis loops, which would be in e es ing o senso and
high equency applica ions.
Wo k suppo ed by NANOKOP N . ITMS 26110230061
NanoCEXma N . ITMS 26220120019 p ojec s, he Slo ak
Agency o he Resea ch and De elopmen (P ojec Nos.
APVV-0266-10 and APVV-0492-11), MNT ERA NET II
STREAM, he Spanish MINECO and EU FEDER (P ojec
No. MAT 2013-45165-P), and he PAI o he Regional
Go e nmen o Andaluc
ıa (P ojec No. P10-FQM-6462).
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FIG. 4. P obabili y dis ibu ion o aniso opy ields om he second de i a-
i e o he magne iza ion cu e om sa u a ion o emanence (da a shown
co espond o a smoo hing using en neighbo ing poin s).
17A301-3 Bl
azquez e al. J. Appl. Phys. 117, 17A301 (2015)
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