Ci a ion: Salaheldeen, M.; Ipa o , M.;
Co e-Leon, P.; Zhuko a, V.; Zhuko ,
A. E ec o Annealing on he
Magne ic P ope ies o
Co2MnSi-Based Heusle Alloy
Glass-Coa ed Mic owi es. Me als
2023,13, 412. h ps://doi.o g/
10.3390/me 13020412
Academic Edi o s: Mau o Gio annini
and Ji o Ki agawa
Recei ed: 9 Decembe 2022
Re ised: 9 Feb ua y 2023
Accep ed: 14 Feb ua y 2023
Published: 16 Feb ua y 2023
Copy igh : © 2023 by he au ho s.
Licensee MDPI, Basel, Swi ze land.
This a icle is an open access a icle
dis ibu ed unde he e ms and
condi ions o he C ea i e Commons
A ibu ion (CC BY) license (h ps://
c ea i ecommons.o g/licenses/by/
4.0/).
me als
A icle
E ec o Annealing on he Magne ic P ope ies o
Co2MnSi-Based Heusle Alloy Glass-Coa ed Mic owi es
Mohamed Salaheldeen 1,2,3,4,* , Mihail Ipa o 1,2,4 , Paula Co e-Leon 1,2,4 , Valen ina Zhuko a 1,2,4
and A cady Zhuko 1,2,4,5,*
1Depa amen o de Políme os y Ma e iales A anzados, Facul ad Química, Uni e sidad del País Vasco,
UPV/EHU, 20018 San Sebas ián, Spain
2Depa amen o de Física Aplicada, EIG, Uni e sidad del País Vasco, UPV/EHU, 20018 San Sebas ián, Spain
3Physics Depa men , Facul y o Science, Sohag Uni e si y, Sohag 82524, Egyp
4EHU Quan um Cen e , Uni e si y o he Basque Coun y, UPV/EHU, 20018 San Sebas ián, Spain
5IKERBASQUE, Basque Founda ion o Science, 48011 Bilbao, Spain
*Co espondence: [email p o ec ed] (M.S.); [email p o ec ed] (A.Z.)
Abs ac :
In he cu en s udy, we concen a ed on he in luence o annealing on he magne ic beha -
io o Co
2
MnSi-based Heusle mic owi es. We se he annealing empe a u e a 1023 K o 2 h, as
he sample did no show any signi ican changes in he magne ic p ope ies a lowe empe a u es,
while annealing a empe a u es abo e 1023 K damages he glass coa ing. S ong in-plane magne-
oc ys alline aniso opy pa allel o he mic owi e axis was e iden in he magne ic beha io a oom
empe a u e o as-p epa ed and annealed samples. The coe ci i y o he annealed sample was ou
imes highe han ha o he as-p epa ed sample ac oss a wide ange o measu ing empe a u es.
Bo h annealed and as-p epa ed samples exhibi qui e s able coe ci i y beha io wi h empe a u e,
which may ha e in e es ing applica ions. The an nealed sample did no exhibi magne ic sa u a ion
o M-H loops measu ed below 50 K. Sha p i e e sible magne ic beha io has been de ec ed o
annealed samples a a blocking empe a u e o 220 K; a he same ime, he blocking empe a u e
o he as-p epa ed sample was 150 K. The s ong in e nal mechanical s ess induced du ing he
ab ica ion o Co
2
MnSi mic owi es in addi ion o he in e nal s ess elaxa ion caused by he annealing
induced he onse o magne ic phases esul ing in unusual and i e e sible magne ic beha io .
Keywo ds:
Heusle alloys; glass-coa ed mic owi es; magne ic p ope ies; annealing; blocking empe a u e
1. In oduc ion
Amo phous and nanoc ys alline glass-coa ed mic o- and nanowi es a e pa icula ly in-
iguing ma e ials in e ms o bo h heo y and echnological applica ions. Taylo de eloped
a s aigh o wa d manu ac u ing p ocess o cas ing sho samples o glass-coa ed mic o-
and nanowi es in 1924 [
1
]. This me hod was la e (be ween 1950 and 1964) ex ensi ely
modi ied by Uli o sky, who p o ided a ecei ing bobbin, which enabled he p epa a ion o
qui e long (almos con inuous) glass-coa ed mic owi es [
2
]. La ge quan i ies o hese mi-
c owi es may be p oduced using he modi ied Taylo –Uli o sky p ocess [
3
]. Addi ionally,
he mode n ab ica ion acili y o glass-coa ed mic owi e p epa a ion is p o ided wi h a
eedback sys em ha allows o p ecise con ol o he mic owi e geome y (me allic nucleus
diame e , d, and he o al o all mic owi e diame e s, D) using a PC [
4
]. Acco dingly, s udies
o glass-coa ed mic owi es ha e a ac ed subs an ial in e es in ecen yea s, la gely due o
hei echnical uses, pa icula ly as senso componen s in a ious sys ems [
5
]. Mic owi es
play a signi ican ole in a a ie y o applica ions, he majo i y o which a e connec ed o
wi eless elecommunica ions sys ems, such as sa elli e global posi ioning, b oadcas sa el-
li e ele ision, and cellula elephones as well as a ious magne ic senso s. Rada sys ems
a e also pa icula ly help ul o a numbe o emo e sensing sys ems, including ai a ic
con ol ada , missile acking ada , and sea ada o iden i ying mo ing a ge s [
3
–
5
].
Me als 2023,13, 412. h ps://doi.o g/10.3390/me 13020412 h ps://www.mdpi.com/jou nal/me als
Me als 2023,13, 412 2 o 14
Fe omagne ic-based, glass-coa ed mic owi es a e among he mos p omising unc ional
magne ic ma e ials, because o hei unique combina ion o physical (mechanical, magne ic,
and an ico osi e) quali ies and hei as , low-cos p epa a ion me hod [3,6].
Among he p omising e omagne ic alloys a e Heusle alloys, which ha e composi-
ions o X
2
YZ ( ull-Heusle ) o XYZ (hal -Heusle ), whe e X and Y a e ansi ion me als
and Z is he majo g oup elemen ; hese belong o a ca ego y o ma e ials ha ing se e al
applica ions [
7
]. Due o he p esence o a band gap a ound he Fe mi ene gy, he majo i y
o he spin bands in his class o ma e ials exhibi me allic beha io , while he mino i y o
he spin bands exhibi semiconduc ing o insula ing ea u es [
8
–
10
]. The e o e, a he Fe mi
le el, hese ma e ials exhibi nea ly 100% spin pola iza ion [11].
Due o hei high Cu ie poin (Tc > 1200 K), adjus able band s uc u e, and low
magne ic damping coe icien s, Co-based Heusle compounds a e among he mos p omis-
ing ma e ials o mul i unc ional applica ions [
12
–
14
]. Because o he signi ican Be y
cu a u e associa ed wi h hei band s uc u e, hese alloys also exhibi ema kable and
anomalous physical cha ac e is ics abo e and below oom empe a u e [
15
,
16
]. As a esul ,
Co-based Heusle compounds a e gaining he in e es o he scien i ic communi y, and
ex ensi e s udies and in es iga ions ha e been ca ied ou . Co
2
MnSi is a s ong op ion
o an ad anced spin onic de ice, because o i s high band gap o mino i y spins (0.5 o
0.8 eV), high Cu ie empe a u e (985 K), high unnel magne o esis ance, la ge magne o esis-
ance a ios, and pe pendicula magne ic aniso opy [
17
–
20
]. In he las wo decades, bo h
expe imen al and heo e ical esea ch on Co
2
MnSi ha e concen a ed on he examina ion
o i s s uc u al and magne ic cha ac e is ics and on hei ela ionship o spin pola iza-
ion [
21
–
23
]. By using ul a iole -pho oemission spec oscopy, he maximum alue o spin
pola iza ion o bulk Co
2
MnSi (93%) was ound a oom empe a u e [
24
]. The p ope ies
men ioned abo e make he Co
2
MnSi Heusle alloy one o he mos in es iga ed Co-based
Heusle compounds and a sui able ma e ial o spin onic applica ions.
A c mel ing is he mos widely used me hod o ab ica ing he magne ic Heusle
alloy, ollowed by he mal ea men o enhance i s physical s uc u e [
25
,
26
]. Using his
echnique, i was possible o c ea e la ge-scale Heusle alloys wi h adjus able chemical
composi ions. Addi ionally, acco ding o epo s elsewhe e [
26
,
27
], se e al p ocesses a e
used o p oduce Heusle alloys in a a ie y o o ms, including hin ilms, nanopa i-
cles, ibbons, and nanos uc u ed ma e ials. As p e iously men ioned, minia u iza ion
allows o he modi ica ion and enhancemen o se e al physical ea u es o bulk Heusle
alloys [26,28–31].
Howe e , he e a e a numbe o issues and di icul ies wi h he p epa a ion o any
p ospec i e “mul i unc ion and sma ” Heusle alloy. The i s in ol es la ge-scale p oduc-
ion o alloys made om Heusle compounds ha ha e he exac same chemical make-up
and physical cha ac e is ics. In addi ion, specialized p ocesses a e expensi e and demand
ex emely p ecise physical equi emen s (ul a-high acuum, p essu e, powe , high em-
pe a u e, and a speci ic subs a e). Mode n Taylo –Uli o sky ab ica ion acili ies make i
possible o ab ica e ul a- hin and uni o m glass-co e ed mic owi es, a composi e ma e ial
consis ing o a me allic nucleus (diame e 0.1–100
µ
m) co e ed by a glass coa ing ( hickness
2–30
µ
m) [
3
,
32
]. I is a e y p omising app oach o he c ea ion o mul i unc ional, sma
ma e ials o a wide a ie y o applica ions, due o he low cos o la ge-scale manu ac u -
ing (i.e., many kilome e s om a iny ingo (5 g)). Fu he mo e, he e sa ili y o c ea ing
Heusle -based, glass-coa ed mic owi es wi h a ious s uc u es, including amo phous,
nanoc ys alline, and g anula , o e s a special oppo uni y o s udy he impac o a ious
mic os uc u e ypes o he same ma e ial on i s physical p ope ies [
32
–
38
]. Addi ionally,
a lexible, insula ing, con inuous glass coa ing o e s elec ical sho -ci cui p o ec ion,
enabling he usage o Heusle -based, glass-coa ed mic owi es in en i onmen s wi h ha sh
chemicals, as well as o e ing biocompa ibili y o Heusle alloys’ o en biologically incom-
pa ible s uc u e [
39
–
41
]. Howe e , o he bes o ou knowledge, such p omising Heusle
alloys, i.e., Co
2
MnSi-based, glass-coa ed mic owi es, ha e no been in es iga ed be o e.
The e o e, we conside his s udy, along wi h ou p e ious s udy [
42
], o be pionee ing
Me als 2023,13, 412 3 o 14
in es iga ions aimed a e ealing he main magne o-s uc u al p ope ies o Co
2
MnSi glass-
coa ed mic owi es. Some magne ic and s uc u al p ope ies, such coe ci i y, empe a u e
s abili y, and i e e sibili y beha io ha e no been ound in Co
2
MnSi in o he physical
o ms, such as hin ilms [
17
–
23
]. An impo an poin o hese di e ences is he unique
in e nal mechanical s ess dis ibu ion, which is induced du ing he ab ica ion p ocess and
de e mines he magne o-s uc u al beha io . This kind o in e nal s ess dis ibu ion can be
easily con olled du ing he ab ica ion p ocess. In ou p e ious s udy, we illus a ed he
magne o-s uc u al p ope ies o as-p epa ed Co
2
MnSi glass-coa ed mic owi es [
42
]. In he
cu en s udy, we ocused on he e ec o he mal annealing on he magne ic p ope ies
o Co
2
MnSi glass-coa ed mic owi es. We ound ha annealing g ea ly e ec s magne ic
beha io . In addi ion, we ound s able magne ic and s uc u al beha io o annealing
empe a u es below T = 1023 K.
2. Ma e ials and Me hods
The acile e apo a ion o Mn, which would a ec he ac ual nominal composi ion a io,
made i di icul o ab ica e Co
2
MnSi glass-coa ed mic owi es wi h a a io o (2:1:1), i.e.,
Co
50
Mn
25
Si
25
. As a esul , we began by employing a adi ional a c u nace and addi ional
Mn mass o make he Co
2
MnSi alloy. To p e en he Co
2
MnSi alloy om oxidizing du ing
he mel ing p ocess, we mel ed high-pu i y me als Co (99.99%), Si (99.99%), and Mn
(99.99%) supplied by Technoamo S.R.L. Co. (Tu ku, Finland) unde acuum and in
an a gon en i onmen . Fi e mel ing cycles we e equi ed o p oduce a uni o m, highly
homogenous Co
2
MnSi alloy. A e wa ds, we used Scanning Elec on Mic oscopy (SEM)
and Ene gy Dispe si e X- ay (EDX) (JEOL-6610LV, JEOL L d., Tokyo, Japan) o de e mine
he nominal chemical composi ion o he Co
2
MnSi alloy. Once we had he co ec alloy
composi ion, we began he manu ac u e o Co
2
MnSi glass-coa ed mic owi es using he
Taylo –Uli o sky app oach a e con i ming he nominal a io o (2(Co):1(Mn):1(Si)), which
en ailed d awing and cas ing s aigh om he mel ed Co
50
Mn
25
Si
25
alloy as de ailed
elsewhe e [
42
–
44
]. A glass capilla y was o med a e a high equency induc o hea ed an
ingo o e i s mel ing poin . This glass capilla y was hen illed wi h he mol en Co2MnSi
alloy, pulled ou , and w apped on o a e ol ing pick-up bobbin [
3
,
43
,
45
]. The diame e
o he me allic nuclei, d, was go e ned by he speed o wi e d awing and he speed o he
pick-up bobbin o a ion. Addi ionally, passing he p oduced mic owi e h ough a coolan
s eam esul ed in apid mel quenching [
43
,
46
]. We e alua ed he geome ic cha ac e is ics
o Co
2
MnSi glass-coa ed mic owi es using SEM, whe e he me allic nucleus diame e o
he Co
2
MnSi p oduced mic owi e was d
nuclei
= 10.2
±
0.1
µ
m and he o e all diame e
D
o al
= 22.2
±
0.1
µ
m. The mos in iguing aspec o he manu ac u ing me hod is ha ,
du ing he apid solidi ica ion p ocess, he me allic nuclei we e su ounded by a glass
laye , p o ec ing hem om oxida ion and making his he pe ec p ocedu e o Mn-based
alloys. Addi ionally, such a p ocess is linked o ele a ed in e nal s esses b ough on by
apid quenching i sel , by d awing s esses, and by he in e nal s ess o igina ing om he
di e en he mal expansion coe icien s o he glass and he me allic nuclei [
5
,
44
,
47
–
50
].
A e p epa a ion o he Co
2
MnSi glass-coa ed mic owi es, annealing was pe o med a
1023 K o wo hou s in a con en ional u nace in an ai a mosphe e (insula ing glass-
coa ing o e s excellen oxida ion p o ec ion). A an annealing empe a u e, T
ann
, abo e
1023 K and an annealing ime abo e 2 h a T
ann
= 1023 K, he glass-coa ing o Co
2
MnSi glass-
coa ed mic owi e begins o be damaged and, a a highe T
ann
, can comple ely disappea .
Thus, we only ocused on he annealing condi ions whe e glass-coa ed mic owi es we e
no ye damaged. As p e iously epo ed, annealing condi ions (T
ann
, and ime annealing,
ann
) and e en cooling condi ions a e annealing a e impo an . The e o e, in his case, o
educe diso de and in e nal s esses, we applied slow (wi h a u nace) cooling [
43
]. Nex ,
he chemical composi ions o he samples we e de e mined by EDX. The a e age chemical
composi ion o a ound Co
51
Mn
23.9
Si
25.1
p o ed he alidi y o he nominal a io (2:1:1),
and he eal chemical composi ion was de e mined by analyzing he di e en 10 poin s as
de ailed in ou ea lie s udy [
42
]. Recen ly, X- ay Di ac ion (XRD) BRUKER (D8 Ad ance,
Me als 2023,13, 412 4 o 14
B uke AXS GmbH, Ka ls uhe, Ge many) was used o in es iga e he mic os uc u e o
as-p epa ed Co
2
MnSi glass-coa ed mic owi es and analyze he phase con en (no shown in
cu en wo k) [
42
]. The annealed sample showed almos he same XRD p o ile and appa en
s uc u e as epo ed in ou p e ious wo k o as-p epa ed samples [
42
]. The ield cooling
and ze o- ield cooling magne iza ion cu es o empe a u es anging om 5 K o 350 K
wi h an applied ex e nal magne ic ield o 100 Oe, as well as he oom empe a u e and
he mal magne ic beha io o Co2MnSi glass-coa ed mic owi e samples we e de e mined
using he Physical P ope y Magne ic Sys em, PPMS (Quan um Design Inc., San Diego,
CA, USA).
3. Resul s
3.1. Mic os uc u e Analysis
Mic os uc u e analysis was pe o med using EDX/SEM and XRD o check he chemi-
cal composi ion and s uc u e o he as-p epa ed and annealed samples. Fo he chemical
composi ion, he s udy o he a ious 10 poin s yielded he ue chemical composi ion,
and he nominal a io (2:1:1) s accep ed since he a e age chemical composi ion was abou
Co
51
Mn
23.9
Si
25.1
o he annealed and as-p epa ed sample as desc ibed in [
43
]. F om he
XRD analysis we e alua ed he a e age g ain size, D
g
, using he Debye–Sche e equa ion
o sample annealed a 1023 K o 2h and compa ed he esul s wi h he D
g
alue o he
as-p epa ed sample epo ed in [43]. The esul s a e p o ided in Table 1.
Table 1. A e age g ain size (nm) o annealed and as-p epa ed Co2MnSi glass-coa ed mic owi e.
Sample Dg(nm)
As-p epa ed 46.2
Annealed a 923 K 50.3
Annealed a 1023 K 64.2
As illus a ed in Table 1, he D
g
o he samples annealed o 2 h a 923 K and 1023 K
was highe han ha o he as-p epa ed sample. Fo he sample annealed a 923 K (2 h),
D
g
inc eased om 46.1 nm o 50.3 nm, i.e., became only 4.2 nm highe han ha o he
as-p epa ed sample. Fo he sample annealed a 1023 K (2 h), a no able inc ease in D
g
o
abou 18.1 nm was obse ed, i.e., mo e han ou imes highe han he inc emen obse ed
o he sample annealed a 923 K (2 h) (see Table 1).
As discussed elsewhe e, usually he de i i ica ion o amo phous Fe- ich ma e ials
by annealing abo e he c ys alliza ion empe a u e ( ypically abo e 823 K) is associa ed
wi h bo h inc easing g ain size and c ys alline olume ac ion [
50
]. This kind o endency
in a e age g ain size has also been p e iously obse ed in Fe- ich (Fineme - ype) glass-
coa ed mic owi es [
51
]. Howe e , in mic owi es wi h a nanoc ys alline s uc u e ob ained
di ec ly in as-p epa ed samples, he e olu ion o he a e age g ain size upon annealing
does no always ollow his endency: in some cases (nanoc ys alline Fe–P mic owi es),
he a e age g ain size did no change conside ably upon annealing [
52
], while e en a
subs an ial a e age g ain size e inemen has been epo ed in he case o nanoc ys alline
Hi pe m-like mic owi es [
53
]. In discussions o his kind o D
g
e inemen , p oposed
mechanisms ha e included ei he massi e nuclea ion o small g ains upon annealing o
e en dissolu ion o he uns able c ys alline phases and he nuclea ion and g ow h o mo e
s able nanoc ys als [
53
,
54
]. Addi ionally, as discussed elsewhe e [
52
], he ele a ed in e nal
s esses induced du ing he ab ica ion p ocess can a ec he ec ys alliza ion p ocess
o ma e ials p epa ed using apid mel -quenching me hods, due o he nonequilib ium
he modynamics con ibu ion. Indeed, he ec ys alliza ion p ocess is subs an ially a ec ed
by a omic di usion unde s ess [
55
]. As men ioned abo e, he unique ea u e o he glass-
coa ed mic owi es is hei ele a ed in e nal s esses, which can a ec he c ys alliza ion
p ocess o such mic owi es [
43
,
52
,
54
]. In he p esen case, he beha io o D
g
looks simila
o he case o Fe
64.7
P
33.3
B
2
glass-coa ed mic owi es, whe e only a sligh annealing e ec
Me als 2023,13, 412 5 o 14
on he Dg alue was obse ed o ce ain annealing empe a u e anges. A sligh inc ease
obse ed in D
g
is esponsible o a mino change in he magne ic p ope ies o he sample
annealed a 923 K (2 h) and o a signi ican change a 1023 K (2 h) as compa ed o he
as-p epa ed sample, as will be illus a ed in he magne ic cha ac e iza ion sec ion.
3.2. Room Tempe a u e Magne ic P ope ies
To es he magne ic aniso opy a oom empe a u e, he magne ic hys e esis (M-H)
loops o Co
2
MnSi glass-coa ed mic owi e (as-p epa ed and annealed) we e measu ed
a oom empe a u e o wo dis inc applied ex e nal magne ic ield di ec ions. Fi s ,
we measu ed M-H loops when H was pa allel o he axis o he Co
2
MnSi glass-coa ed
mic owi e (i.e., in-plane, IP) and pe pendicula o i in he second case (i.e., a an angle o
90 deg ees, o ou -o -plane, OOP). As can be app ecia ed om Figu e 1a,b, bo h samples
show M-H cu es wi h sa u a ion ypical o e omagne ic beha io and consis en wi h
a Cu ie poin p e iously epo ed o hese alloys o be well abo e oom empe a u e
(
Tc= 985 K) [17]
. All hys e esis loops we e no malized o he maximum magne ic momen
o con enience in compa ison. Acco ding o Figu e 1a,b, bo h as-p epa ed and annealed
Co
2
MnSi glass-coa ed mic owi es exhibi s ong uniaxial magne ic aniso opy, as e idenced
by he conside able di e ence be ween he axial and ou -o -axis hys e esis loops. Bo h
samples ha e conside able emanen magne iza ion in axial hys e esis loops, compa ed o
he ou -o -axis hys e esis loop, which exhibi s a linea magne ic beha io and a emanence
magne iza ion ha is close o ze o. As a esul , he ha d di ec ion o magne iza ion is
pe pendicula o he mic owi e axis, while he easy di ec ion is pa allel o i . Magne ic
aniso opy is e idenced by he beha io o he axial and ou -o -axis hys e esis loops. The
annealed sample shows highe alues o all magne ic pa ame e s ha can be ex ac ed
om he M-H loops. The coe ci i y, H
c
, educed emanence, M
, and he aniso opy ield,
H
k
, o bo h di ec ions (IP and he OOP) a e summa ized in he Table 2. The main poin
is ha he annealed sample p esen s di e en magne ic pe o mance compa ed o he
as-p epa ed sample and ha annealing a ec s he magne ic mic os uc u e o Co
2
MnSi
mic owi es and he in e nal s esses induced du ing he ab ica ion p ocess. Howe e , i
seems ha he annealing condi ions do no ha e a s ong impac on he magne ic beha io
o he as-p epa ed sample, since o e all magne ic beha io has a simila ea u e.
Me als 2023, 13, x FOR PEER REVIEW 6 o 14
Figu e 1. Co2MnSi glass-coa ed mic owi es, bo h as-p epa ed samples (a) and samples annealed a
1023 K o (2 h) (b) ;in-plane (pa allel o he wi e axis, black loop) and ou -o -plane (pe pendicula
o he wi e axis, ed loop) hys e esis loops we e measu ed a oom empe a u e.
Table 2. The magne ic pa ame e s o Co2MnSi glass-coa ed mic owi es o as-p epa ed and annealed
samples in IP and OOP di ec ions.
Samples Hc (Oe) M Hk (Oe)
IP OOP IP OOP IP OOP
As-p epa ed 9 ± 2 43 ± 2 0.27 ±
0.01
0.02 ±
0.01 440 ± 5 7655 ± 4
Annealed 24 ± 2 56 ± 3 0.15 ±
0.01
0.08 ±
0.01 3200 ± 3 9 720 ± 3
3.3. Tempe a u e Dependence o Magne ic Beha io
3.3.1. Ze o Field Cooling, Field Cooling, and Field Hea ing Magne ic P ope ies
I is c i ical o examine he en i e magne ic beha io o he Co2MnSi glass-coa ed mi-
c owi e a a ious empe a u es in o de o assess i s he mal s abili y, a c ucial physical
cha ac e is ic ha will help o e alua e i s po en ial in e es o spin onics applica ions.
Tempe a u e dependence can also be a aluable indica o o whe he a magne ic phase
ansi ion is e en a possibili y. Using a low magne ic ield (H = 100 Oe) and a empe a u e,
T, ange o 5 o 350 K, we in es iga ed he magne iza ion dependence on empe a u e (M
s. T), i.e., ze o ield cooling (ZFC), ield cooling (FC), and ield hea ing (FH) p o ocols o
he as-p epa ed and annealed Co2MnSi glass-coa ed mic owi es, as shown in Figu e 2.
The as-p epa ed and annealed Co2MnSi glass-coa ed mic owi e samples we e cooled
o 5 K unde an applied magne ic ield (H = 100 Oe), causing he andom magne ic mo-
men ec o s o eeze pa allel o he applied ield a low empe a u es. Fo he as-p e-
pa ed sample, almos pe ec ma ching be ween he ZFC, FC, and FH was obse ed (see
Figu e 2a). The in e es ing poin is ha all magne iza ion cu es o he as-p epa ed sample
exhibi la ge, i e e sible magne ic beha io whe e he change in he magne ic endency
occu s a he blocking empe a u e (200 K). The same magne iza ion beha io o ZFC, FC,
and FH ha e been obse ed o annealed samples a 923 K (2h) (see Figu e 2b). The e is
only a sligh misma ch be ween he ZFC, FC, and FH magne iza ion cu es abo e and
below he blocking empe a u e. In addi ion, he ZFC and FH magne iza ion cu es o e -
lap he FC cu e a a empe a u e ange 50 K–350 K. This di e ence mus be a ibu ed o
he changing mic os uc u e o he Co2MnSi glass-coa ed mic owi e du ing annealing. Fo
he annealed sample a 1023 K (2 h), he ZFC, FC, and FH magne iza ion cu es exhibi
complex magne ic beha io compa ed o he as-p epa ed sample. As shown in Figu e 2c
ZFC, FC, and FH magne iza ion cu es exhibi a misma ch. Fo he ZFC magne iza ion
cu e, no malized magne iza ion s a s o dec ease wi h dec easing empe a u e T wi hin
a ange o 350 K o 280 K; i hen s a s inc easing wi h dec easing empe a u e, eaching
Figu e 1.
Co
2
MnSi glass-coa ed mic owi es, bo h as-p epa ed samples (
a
) and samples annealed a
1023 K o (2 h) (
b
); in-plane (pa allel o he wi e axis, black loop) and ou -o -plane (pe pendicula o
he wi e axis, ed loop) hys e esis loops we e measu ed a oom empe a u e.
Due o he p esence o c ys alline phases and he o me magne ic aniso opy o
he mic owi e, he e a e wo p ima y sou ces o his high magne ic aniso opy: cubic
magne oc ys alline aniso opy and uniaxial magne ic aniso opy, espec i ely [
47
,
49
,
56
].
The axial hys e esis loop does no ha e a p ecise squa ed o m, as s a ed o he aniso opic
ma e ials, as illus a ed in Figu e 1. The p esence o he amo phous and c ys alline phases
(see [
43
]) in ou si ua ion is wha causes he impe ec squa ed hys e esis loop. No ably, he
Me als 2023,13, 412 6 o 14
same inding was ecen ly no ed in ou ea lie wo k using glass-coa ed mic owi es wi h a
Co
2
-based Heusle alloy [
32
]. Addi ionally, ou indings coincide wi h indings o hin
ilms made o Co2-based Heusle alloys ound elsewhe e [38].
Table 2.
The magne ic pa ame e s o Co
2
MnSi glass-coa ed mic owi es o as-p epa ed and annealed
samples in IP and OOP di ec ions.
Samples Hc(Oe) M Hk(Oe)
IP OOP IP OOP IP OOP
As-p epa ed 9 ±2 43 ±2 0.27 ±0.01 0.02 ±0.01 440 ±5 7655 ±4
Annealed 24 ±2 56 ±3 0.15 ±0.01 0.08 ±0.01 3200 ±3 9720 ±3
3.3. Tempe a u e Dependence o Magne ic Beha io
3.3.1. Ze o Field Cooling, Field Cooling, and Field Hea ing Magne ic P ope ies
I is c i ical o examine he en i e magne ic beha io o he Co
2
MnSi glass-coa ed
mic owi e a a ious empe a u es in o de o assess i s he mal s abili y, a c ucial physical
cha ac e is ic ha will help o e alua e i s po en ial in e es o spin onics applica ions.
Tempe a u e dependence can also be a aluable indica o o whe he a magne ic phase
ansi ion is e en a possibili y. Using a low magne ic ield (H = 100 Oe) and a empe a u e,
T, ange o 5 o 350 K, we in es iga ed he magne iza ion dependence on empe a u e (M
s. T), i.e., ze o ield cooling (ZFC), ield cooling (FC), and ield hea ing (FH) p o ocols o
he as-p epa ed and annealed Co2MnSi glass-coa ed mic owi es, as shown in Figu e 2.
The as-p epa ed and annealed Co
2
MnSi glass-coa ed mic owi e samples we e cooled
o 5 K unde an applied magne ic ield (H = 100 Oe), causing he andom magne ic momen
ec o s o eeze pa allel o he applied ield a low empe a u es. Fo he as-p epa ed
sample, almos pe ec ma ching be ween he ZFC, FC, and FH was obse ed (see Figu e 2a).
The in e es ing poin is ha all magne iza ion cu es o he as-p epa ed sample exhibi
la ge, i e e sible magne ic beha io whe e he change in he magne ic endency occu s
a he blocking empe a u e (200 K). The same magne iza ion beha io o ZFC, FC, and
FH ha e been obse ed o annealed samples a 923 K (2h) (see Figu e 2b). The e is only
a sligh misma ch be ween he ZFC, FC, and FH magne iza ion cu es abo e and below
he blocking empe a u e. In addi ion, he ZFC and FH magne iza ion cu es o e lap he
FC cu e a a empe a u e ange 50 K–350 K. This di e ence mus be a ibu ed o he
changing mic os uc u e o he Co
2
MnSi glass-coa ed mic owi e du ing annealing. Fo
he annealed sample a 1023 K (2 h), he ZFC, FC, and FH magne iza ion cu es exhibi
complex magne ic beha io compa ed o he as-p epa ed sample. As shown in Figu e 2c
ZFC, FC, and FH magne iza ion cu es exhibi a misma ch. Fo he ZFC magne iza ion
cu e, no malized magne iza ion s a s o dec ease wi h dec easing empe a u e T wi hin
a ange o 350 K o 280 K; i hen s a s inc easing wi h dec easing empe a u e, eaching
a maximum alue a T = 210 K. A sha p dec ease in no malized magne iza ion has been
obse ed wi h dec easing empe a u e, whe eby a minimum alue was de ec ed a
T=5K
.
This sha p dec ease in no malized magne iza ion indica es la ge, i e e sible magne ic
beha io a a blocking empe a u e o a ound 210 K. Abo e his blocking empe a u e, he
FC and FH cu es show a di e en magne ic endency when he empe a u e lies wi hin
a ange o 350 K o 250 K. A his poin , he FC and FH ha e he same endency when T
dec eases below 250 K. These di e ences in he magne ic beha io o he ZFC, FC, and
FH a e s ongly ela ed o he change in he mic os uc u e o he samples wi h changing
he empe a u e. Such magne ic i e e sibili y has been shown in Co
2
-based Heusle
alloy glass-coa ed mic owi es [
32
,
36
–
38
]. This i e e sibili y is highly in luenced by he
mic omagne ic s uc u e o he magne ic ma e ials. Addi ionally, i appea s o be he esul
o he coexis ence o con en ional e-en an e omagne ism and spin glass- ype ac i i y, as
p e iously obse ed [
38
,
56
]. Fu he mo e, he diso de ed s uc u e (B2 phase) and chemical
makeup o Co
2
MnSi glass-coa ed mic owi es a ec he i e e sibili y beha io , causing he
magne ic g ound s a e o ha e a s ong an i e omagne ic con ibu ion, pa icula ly a low
Me als 2023,13, 412 7 o 14
empe a u es o Mn–Mn in e ac ion and andom spin diso de (B2 phase), which is also
ound wi h he e omagne ic o de (L21phase) [17,56].
Me als 2023, 13, x FOR PEER REVIEW 7 o 14
a maximum alue a T = 210 K. A sha p dec ease in no malized magne iza ion has been
obse ed wi h dec easing empe a u e, whe eby a minimum alue was de ec ed a T = 5
K. This sha p dec ease in no malized magne iza ion indica es la ge, i e e sible magne ic
beha io a a blocking empe a u e o a ound 210 K. Abo e his blocking empe a u e, he
FC and FH cu es show a di e en magne ic endency when he empe a u e lies wi hin
a ange o 350 K o 250 K. A his poin , he FC and FH ha e he same endency when T
dec eases below 250 K. These di e ences in he magne ic beha io o he ZFC, FC, and
FH a e s ongly ela ed o he change in he mic os uc u e o he samples wi h changing
he empe a u e. Such magne ic i e e sibili y has been shown in Co2-based Heusle alloy
glass-coa ed mic owi es [32,36–38]. This i e e sibili y is highly in luenced by he mic o-
magne ic s uc u e o he magne ic ma e ials. Addi ionally, i appea s o be he esul o
he coexis ence o con en ional e-en an e omagne ism and spin glass- ype ac i i y, as
p e iously obse ed [38,56]. Fu he mo e, he diso de ed s uc u e (B2 phase) and chem-
ical makeup o Co2MnSi glass-coa ed mic owi es a ec he i e e sibili y beha io , caus-
ing he magne ic g ound s a e o ha e a s ong an i e omagne ic con ibu ion, pa icu-
la ly a low empe a u es o Mn–Mn in e ac ion and andom spin diso de (B2 phase),
which is also ound wi h he e omagne ic o de (L21 phase) [17,56].
Figu e 2. Ze o ield cooling (ZFC), ield cooling (FC) and ield hea ing (FH) o Co2MnSi glass-coa ed
mic owi es, bo h as-p epa ed samples (a) and samples annealed a 923 K (2 h) and 1023 K (2 h) (b)
and (c), espec i ely.
0 50 100 150 200 250 300 350
0.0
0.2
0.4
0.6
0.8
1.0
ZFC
FC
FH
H = 100 Oe
No malized magne iza ion
T (K)
As-p epa ed
(a)
0 50 100 150 200 250 300 350
0.0
0.2
0.4
0.6
0.8
1.0
1023 K H = 100 Oe
(c)
No malized magne iza ion
T (K)
ZFC
FC
FH
0 50 100 150 200 250 300 350
0.0
0.2
0.4
0.6
0.8
1.0
ZFC
FC
FH
H = 100 Oe
No malized magne iza ion
T (K)
(b)
923 K
Figu e 2.
Ze o ield cooling (ZFC), ield cooling (FC) and ield hea ing (FH) o Co
2
MnSi glass-coa ed
mic owi es, bo h as-p epa ed samples (
a
) and samples annealed a 923 K (2 h) and 1023 K (2 h) (
b
)
and (c), espec i ely.
3.3.2. M-H Loops
A his sec ion we ocused on he M-H beha io o he as-p epa ed sample and
sample annealed a 1023 K (2 h), whe e a no able di e ence in he magne iza ion cu es has
been obse ed as illus a ed a Figu e 2. The magne ic hys e esis beha io o as-p epa ed
and annealed Co
2
MnSi glass-coa ed mic owi es ac oss a wide ange o empe a u es
(400 K o 5 K) is summa ized in Figu es 3and 4. All he M-H loops a e ep esen ed as
M/M
5K
o a be e compa ison o he magne ic beha io o he samples, whe e M
5K
is he
maximum magne ic momen ob ained a 5K. The no malized M/M
5K
– alues a e ob ained
by no malizing he maximum magne ic momen a di e en T alues o he M
5K
alue. As
shown in Figu es 3and 4, all samples, i.e., annealed and as-p epa ed, exhibi e omagne ic
beha io due o he ac ha he Cu ie poin is much highe han oom empe a u e.
In addi ion, he annealed samples exhibi lowe no malized sa u a ion magne iza ion
as compa ed o as-p epa ed samples. This change mus be a ibu ed o a change in he
mic omagne ic s uc u e as well as o he mechanical s ess modi ica ion ha can be induced
by annealing. Mo eo e , as-p epa ed Co
2
MnSi glass-coa ed mic owi es yield egula M-H
cu es wi h sa u a ion o empe a u es anging be ween 400 K and 5 K as illus a ed in
Figu es 3and 4. Meanwhile, he annealed sample does no show a sa u a ion s a e e en o
Me als 2023,13, 412 8 o 14
an applied magne ic ield o 30 kOe a empe a u es below 50 K. As shown in Figu e 4, he
slope o he M-H cu es inc eases wi h dec easing empe a u e, eaching a maximum a
5 K (see Figu e 4d). The unusual magne ic beha io o he annealed sample below 50 K
mus be a ibu ed o he e ec o annealing on he changing mic os uc u e o he Co
2
MnSi
glass-coa ed mic owi e. One o he easons o he di e en M-H cha ac e o he annealed
sample can be enhancemen o he an i e omagne ic coupling o Mn-Mn in e ac ion a
low empe a u es.
Me als 2023, 13, x FOR PEER REVIEW 9 o 14
Figu e 3. Co2MnSi glass-coa ed mic owi e magne iza ion cu es (M/M5K) o as-p epa ed samples
(black loops) and samples annealed a 1023 K o 2 h ( ed loops) we e measu ed unde a maximum
ield o 30 kOe and a di e en empe a u es ( om 400 K o 100 K). The inse indica es he loops
wi h low scale o he applied magne ic ield.
-30 -15 0 15 30
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Magne ic Field (kOe)
As-p epa ed
Annealed
400 K
(a)
-30 -15 0 15 30
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Magne ic Field (kOe)
As-p epa ed
Annealed
100 K
( )
-30 -15 0 15 30
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Magne ic Field (kOe)
As-p epa ed
Annealed
150 K
(e)
-30 -15 0 15 30
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Magne ic Field (kOe)
As-p epa ed
Annealed
200 K
(d)
-30 -15 0 15 30
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Magne ic Field (kOe)
As-p epa ed
Annealed
300 K
(c)
-30 -15 0 15 30
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Magne ic Field (kOe)
As-p epa ed
Annealed
350 K
(b)
-0.2 -0.1 0.0 0.1 0.2
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Magne ic Field (kOe)
400 K
-0.2 -0.1 0.0 0.1 0.2
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Magne ic Field (kOe)
350 K
-0.2 -0.1 0.0 0.1 0.2
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Magne ic Field (kOe)
400 K
-0.2 -0.1 0.0 0.1 0.2
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Magne ic Field (kOe)
200 K
-0.2 -0.1 0.0 0.1 0.2
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Magne ic Field (kOe)
150 K
-0.2 -0.1 0.0 0.1 0.2
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Magne ic Field (kOe)
100 K
Figu e 3.
Co
2
MnSi glass-coa ed mic owi e magne iza ion cu es (M/M
5K
) o as-p epa ed samples
(black loops) and samples annealed a 1023 K o 2 h ( ed loops) we e measu ed unde a maximum
ield o 30 kOe and a di e en empe a u es ( om 400 K o 100 K). The inse indica es he loops wi h
low scale o he applied magne ic ield.
Me als 2023,13, 412 9 o 14
Me als 2023, 13, x FOR PEER REVIEW 10 o 14
Figu e 4. Co2MnSi glass-coa ed mic owi e magne iza ion cu es (M/M5K) o as-p epa ed samples
(black loops) and samples annealed a 1023 K o 2 h ( ed loops) measu ed unde a maximum ield
o 30 kOe and a di e en empe a u es ( om 50 K o 5 K). The inse indica es he loops wi h low
scale o he applied magne ic ield.
As desc ibed abo e, he main peculia beha io o glass-coa ed mic owi es in he
p esence o he in e nal s esses is ela ed o he peculia i ies o he ab ica ion p ocess
[43,46,57,58]. The main o igin o such in e nal s esses is ela ed o he di e en he mal
expansion coe icien s o he me allic nuclei and glass-coa ing [3,43,46,57,58]. Howe e ,
he magne oelas ic aniso opy ela ed o hese in e nal s esses can be pa ially eleased
by annealing, while u he c ys alliza ion o he amo phous phase (ei he a e age g ow h
in g ain size o c ys alline phase con en ) o phase ans o ma ion induced by annealing
can also a ec he magne ic beha io o glass-coa ed mic owi es. In he p esen s udy we
ocus only on he e ec o annealing on he magne ic p ope ies. Fu he s udies can help
o unde s and highe coe ci i y o he annealed sample.
-30 -15 0 15 30
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Magne ic Field (kOe)
As-p epa ed
Annealed
20 K
(b)
-30 -15 0 15 30
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Magne ic Field (kOe)
As-p epa ed
Annealed
10 K
(c)
-30 -15 0 15 30
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Magne ic Field (kOe)
As-p epa ed
Annealed
50 K
(a)
-0.2 -0.1 0.0 0.1 0.2
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Ma
g
ne ic Field (kOe)
50 K
-0.2 -0.1 0.0 0.1 0.2
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Ma
g
ne ic Field (kOe)
20 K
-0.2 -0.1 0.0 0.1 0.2
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Ma
g
ne ic Field (kOe)
10 K
-0.2 -0.1 0.0 0.1 0.2
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Ma
g
ne ic Field (kOe)
5 K
-30 -15 0 15 30
-1.0
-0.5
0.0
0.5
1.0
M/M5K
Magne ic Field (kOe)
As-p epa ed
Annealed
5 K
(d)
Figu e 4.
Co
2
MnSi glass-coa ed mic owi e magne iza ion cu es (M/M
5K
) o as-p epa ed samples
(black loops) and samples annealed a 1023 K o 2 h ( ed loops) measu ed unde a maximum ield o
30 kOe and a di e en empe a u es ( om 50 K o 5 K). The inse indica es he loops wi h low scale
o he applied magne ic ield.
F om he M-H cu es measu ed a a ious empe a u es in he 5–400 K ange, bo h o
as-p epa ed and annealed Co
2
MnSi glass-coa ed mic owi es, we can deduce ha empe a-
u e dependence o H
c
and he no malized alues o emanence, M
,
, exhibi ema kable
magne ic beha io . As seen in Figu e 5a, coe ci i y o he annealed sample a 1023 K o
2 h is ou imes highe han ha o he as-p epa ed sample a all measu ing empe a u e
anges. The in e es ing aspec o H
c
beha io is he small change in H
c
wi h changing
T, whe eby a di e ence o a ound 4 Oe and 6 Oe o he as-p epa ed and annealed sam-
ples, espec i ely, is obse ed. Highe coe ci i y alues o he annealed sample can be
ela ed o a ious easons, such as he di e en mic os uc u e o he annealed sample,
he a o emen ioned coexis ence o e omagne ic and an i e omagne ic in e ac ions, o
e en inhomogeneous s ess dis ibu ion ela ed o he ec ys alliza ion p ocess o annealed
samples, which can a ec he magne ic esponse o empe a u e and magne ic ield as
well. The small a ia ion in coe ci i y wi h empe a u e may mani es he unique he mal
s abili y o coe ci i y wi h empe a u e. This ype o H
c
s abili y wi h empe a u e can
be sui able o a ious applica ions. Conce ning he M
empe a u e dependence, bo h
Co
2
MnSi glass-coa ed mic owi e samples yield low alues, whe eby a maximum alue o
a ound 0.24 was de ec ed o he sample annealed a 5 K. The low M
alues indica e ha
he axial magne iza ion is no dominan , and addi ional p e e ed magne iza ion di ec ion
is assumed. Un o una ely, we a e no p esen ly able o de ine he easy magne iza ion
axis o ou samples. As illus a ed in Figu e 5b, M
beha io as a unc ion o T o he
annealed and as-p epa ed samples is qui e unexpec ed compa ed o he beha io o H
c
.
Fo he empe a u e ange o 400–150 K, he as-p epa ed and annealed samples exhibi he
opposi e endency in M
(T) dependencies. The beha io hen comple ely changes when T
