An Isothermal Calorimeter for the direct measurement of magnetocaloric · 2017-10-08 · An...
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An Isothermal Calorimeter for An Isothermal Calorimeter for the direct measurement of the direct measurement of magnetocaloric magnetocaloric properties properties L. Giudici , C.P. Sasso, V. Basso, M. Küpferling, M.Pasquale INRIM Electromagnetics Division, Torino, Italy 31/10/08 L.Giudici Delft days on Magnetocalorics
Transcript of An Isothermal Calorimeter for the direct measurement of magnetocaloric · 2017-10-08 · An...
An
Isot
herm
al C
alor
imet
er fo
r A
n Is
othe
rmal
Cal
orim
eter
for
the
dire
ct m
easu
rem
ent o
f th
e di
rect
mea
sure
men
t of
mag
neto
calo
ricm
agne
toca
loric
prop
ertie
spr
oper
ties
L. G
iudi
ci, C
.P. S
asso
, V. B
asso
, M. K
üpfe
rling
, M.P
asqu
ale
INR
IM E
lect
rom
agne
tics
Div
isio
n, T
orin
o, It
aly
31/1
0/08
L.G
iudi
ci
Del
ft da
ys o
n M
agne
toca
loric
s
31/1
0/08
L.G
iudi
ci
Del
ft da
ys o
n M
agne
toca
loric
s
sam
ple
of
mag
netic
mat
eria
l
sam
ple
of
mag
netic
mat
eria
l
ther
mal
bath
at
tem
pera
ture
Tb
adia
batic
shie
ld qT
mag
netic
field
mag
neto
calo
ricef
fect
entro
pych
ange
tem
pera
ture
cha
nge
T
S
q
Mag
neto
calo
ricE
ffect
Del
ft da
ys o
n M
agne
toca
loric
s
Rev
ersi
ble
Pro
cess
, equ
ilibriu
mco
nditi
ons
Sis
othe
rmal
entro
pych
ange
T aad
iaba
ticte
mpe
ratu
re c
hang
e
Cp
heat
capa
city
in d
iffer
ent
mag
netic
field
s
S(T
)= [S
(T) H
2 -S
(T) H
1] T,P
T ad=
[T(S
) H2-
T(S
) H1] S
,P
Whe
nth
e be
havi
orof
the
tota
l ent
ropy
ofa
mag
netic
solid
iskn
own,
th
e M
CE
isfu
llych
arac
teriz
ed
21
0
()
()
()
TH
HC
TC
TS
TdT
T
2°la
wth
erm
odyn
amic
s
All
quan
titie
sar
e re
late
d:
Pec
hars
kyet
al. P
RB
64
(200
1)
Del
ft da
ys o
n M
agne
toca
loric
s
2 1
(,
)(
)H
MH
H
MT
HS
TdH
T2 1
(,
)(
)(
,)
H
adH
H
TM
TH
TT
dHC
TH
T
Max
wel
l Rel
atio
nshi
ps
V.K
.Pec
hars
kyet
al. P
RB
57,
199
8.
V.K
.Pec
hars
kyet
al. J
AP
86,
1999
.
Tad
31/1
0/08
L.G
iudi
ci
Del
ft da
ys o
n M
agne
toca
loric
s
data
from
A. G
igue
re e
t al.
PR
L 83
, 199
9
phas
e 1
-> F
M, o
rthor
hom
bic
phas
e 0
-> P
M, m
onoc
linic
Irrev
ersi
ble
proc
ess:
firs
t ord
erph
ase
trans
ition
Ent
ropy
prod
uctio
n
Gd5S
i 2Ge 2
Wha
t is
the
entro
py g
ener
ated
al
ong
the
hyst
eres
is lo
op?
1°or
dert
rans
ition
:eq
uilib
rium
ther
mod
ynam
ics
can
beap
plie
d?
Sys
tem
sw
hith
hyst
eres
isin
Tem
pera
ture
and
/or M
agne
ticfie
ld
Not
uniq
uefu
nctio
n
31/1
0/08
L.G
iudi
ci
Irrev
ersi
ble
proc
esse
s:M
easu
rem
ents
Com
paris
onof
resu
ltsof
diff
eren
tmea
sure
men
ts
•is
othe
rmal
entro
pych
ange
•ad
iaba
ticte
mpe
ratu
re c
hang
e
•he
atca
paci
tyin
mag
netic
field
s
How
tode
term
ine
corr
ectly
the
cool
ing
pow
er o
f a M
C
mat
eria
l in
a re
frige
ratio
ncy
cle?
Cp
mea
sure
men
tsan
d m
agne
tizat
ion
mea
sure
men
ts,
usin
gM
axw
ell’s
rela
tions
, de
liver
todi
ffere
ntre
sults
!
Del
ft da
ys o
n M
agne
toca
loric
s
G.J
.Liu
etal
, AP
L 90
(200
1)
Del
ft da
ys o
n M
agne
toca
loric
s
Dire
ct m
easu
rem
ents
of i
soth
erm
al
entro
py c
hang
ePe
ltier c
ell sa
mpl
e
cera
mic
laye
rs
copp
er b
lock
s
vacu
um tu
be
T b
T s
•Pel
tierc
ells
are
used
ashe
atflu
xse
nsor
san
d ac
tuat
ors
forh
eatin
g/co
olin
gth
e sa
mpl
e si
mul
tane
ousl
y
Pel
tiera
sse
nsor
s: h
igh
sens
itivi
tylit
tleaf
fect
edby
the
mag
netic
field
smal
l tim
e co
nsta
nts
Pel
tiera
s ac
tuat
ors:
stri
ct is
othe
rmal
con
ditio
ns e
ven
in
high
er fi
eld
rate
sal
low
s to
mea
sure
S
(H) T
curv
ean
d no
t onl
y in
itial
and
fina
l sta
tes.
Seeb
eck
effe
ct
Pelti
eref
fect
31/1
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iudi
ci
Del
ft da
ys o
n M
agne
toca
loric
s
•the
tem
pera
ture
of t
he th
erm
alba
thca
n be
chan
ged
betw
een
-30°
C a
nd 1
00°C
by
usin
gliq
uid
nitro
gen
and
elec
tric
heat
ers
•set
upin
vac
uum
(0.5
Pa,
rota
rypu
mp)
in o
rder
toav
oid
heat
loss
by
conv
ectio
nof
air
and
chan
geof
te
mpe
ratu
re
•mag
netic
field
prod
uced
byel
ectro
mag
netu
p to
2T
31/1
0/08
L.G
iudi
ci
Del
ft da
ys o
n M
agne
toca
loric
s
Pel
tierc
elle
quat
ions
durin
gm
easu
rem
entt
ime
depe
nden
cepl
ays
a ro
ledu
e to
finite
hea
tcap
acity
of th
e ce
llan
d th
e sa
mpl
e
time
inde
pend
entr
elat
ions
bet
wee
ncu
rren
t, vo
ltage
and
heat
flux
ofa
ther
mo-
elec
tric
mat
eria
l:
Ass
umpt
ion:
fors
mal
lvar
iatio
nsof
the
quan
titie
sin
tim
e (s
mal
lT d
iffer
ence
, slo
wly
time
vary
ing
mag
netic
field
) , th
e eq
uatio
ns1
and
2 ca
n be
appl
ied,
intro
duci
ngce
llde
pend
ent
para
met
ers
Pel
tiere
ffect
Seeb
eck
effe
ct(1
)
(2)
= to
tal s
eebe
ckco
effic
ient
R=
tota
l ele
ctric
resi
stan
ce=T
Pel
tier
coef
ficie
ntK
=th
erm
alco
nduc
tanc
eof
the
colo
umns
T=ab
solu
tete
mpe
ratu
re
31/1
0/08
L.G
iudi
ci
Del
ft da
ys o
n M
agne
toca
loric
sP
eltie
rcel
lequ
atio
ns
Para
met
ers
incl
ude
effe
cts
of fi
nite
hea
tcon
duct
ivity
(incl
usiv
ely
ofco
ntac
t res
ista
nces
)
Equa
tions
appr
opria
te to
desc
ribe
cells
with
fast
resp
onse
: tr
ansi
ents
tate
are
not
desc
ribed
!
fora
sim
plifi
edca
se th
e ce
llpa
ram
eter
sca
n be
dete
rmin
ed:
Cer
amic
laye
rs:
negl
igib
leth
erm
alca
paci
ty, f
inite
ther
mal
cond
uctiv
ityte
mpe
ratu
res
ofba
than
d sa
mpl
e: h
omog
eneo
us(c
heck
sam
ple
case
by
case
)
Pelti
eref
fect
Seeb
eck
effe
ctJo
ule
heat
(neg
ligib
le!)
In o
rder
topa
ss fr
omv
and
ito
Tan
d q s
, th
e ef
fect
ive
para
met
ers
mus
tbe
calib
rate
d!
Effe
ctiv
ece
llco
efic
ient
:
Cal
ibra
tion
Bas
edon
the
equa
tions
3 an
d 4,
a c
alib
ratio
nat
con
stan
ttem
pera
ture
of t
he
ther
mal
bath
ispe
rfor
med
in th
ree
indi
pend
ente
xper
imen
ts:
•cal
ibra
tion
of
•cal
ibra
tion
of
•cal
ibra
tion
of
both
side
sof
cel
lin
cont
act w
ithth
erm
alba
th
pass
ive
conf
igur
atio
n=
Pel
tier
cell
used
ashe
atse
nsor
with
sam
ple
in m
easu
rem
entc
onfig
urat
ion
31/1
0/08
Giu
dici
Del
ft da
ys o
n M
agne
toca
loric
s
(4)
(3)
31/0
10/0
8L.
Giu
dici
Del
ft da
ys o
n M
agne
toca
loric
s
V.B
asso
etal
. Rev
.Sci
.Inst
rum
. 79,
063
907,
(200
8)
Coe
ffici
ents
asa
func
tion
ofth
e te
mpe
ratu
re
Sen
sitiv
ityas
heat
flux
sens
or:
Roo
mTe
mpe
ratu
re:
Sp=
0,10
3 V
/W
Res
olut
ion
on q
=1W
(Usi
nga
nano
voltm
eter
)
Dig
italc
ontro
l for
isot
herm
alco
nditi
ons
The
PI c
ontro
l cha
nges
the
Pel
tierc
ellc
urre
ntin
ord
erto
min
imiz
eth
e te
mpe
ratu
re
diffe
renc
ebe
twee
nsa
mpl
e an
d ba
th:
isot
herm
alw
ithin
5mK
limit:
noi
se
inpu
tP
Iou
tput
IP
TK
,
syst
em
ou
ti
R
0v
futu
re: n
anov
oltm
eter
peak
sat
fiel
dch
ange
poin
ts
31/1
0/08
L.G
iudi
ci
020
4060
8010
012
014
016
018
020
022
024
0-1
0-8-6-4-20246810
T (mK)
time
(s)
activ
e m
easu
rem
ent (
isot
herm
al) o
f G
d 5Si 2.
09G
e 1.91
at 3
05 K
Del
ft da
ys o
n M
agne
toca
loric
s
31/0
10/0
8L.
Giu
dici
Del
ft da
ys o
n M
agne
toca
loric
s
Com
paris
onof
pass
ive
and
activ
em
easu
rem
ents
Gd
T=29
6 K
(T
C=
293
K)
Act
ive:
T
clos
eto
zero
(pea
ksw
hen
q in
cha
ngin
gin
tim
e)
Pas
sive
: T
prop
ortio
nalt
ohe
atflu
x
0
1(
')'
t
es
sq
tdt
mT
Neg
ligib
leen
tropy
prod
uctio
n is
expe
cted
s=es
Sin
gle
valu
edcu
rve
with
no h
yste
resi
s
Hys
etre
sis
effe
ctdu
e to
time
dela
yIn
trodu
ced
byth
e fa
ctth
atsa
mpl
e is
chan
ging
T
Sing
le v
alue
curv
e w
ithno
hys
tere
sis
Test
mea
sure
men
tG
dsa
mpl
e (s
heet
of 5
x5x1
mm
):m
axim
umfie
ld1.
5T, r
ate
20m
T/s
293K
V. B
asso
eta
l., R
ev.S
ci.In
stru
m, 7
9, 0
6390
7, (2
008)
0
1(0
)(
)'
t t
SS
SH
qdt
Tq s
mai
nly
due
toP
eltie
reffe
ct
q s>
0 he
atab
sorb
ed(d
ecre
asin
gfie
ld)
q s<
0 he
atre
leas
ed(in
crea
sing
field
)
-s(
T)
Ope
n po
ints
: mea
sure
men
tspe
rform
edat
Uni
verit
yof
Zara
goza
Del
ft da
ys o
n M
agne
toca
loric
s
31/1
0/08
L.G
iudi
ci
Del
ft da
ys o
n M
agne
toca
loric
sA
ctiv
em
easu
rem
ents
Bar
ium
ferr
ite B
aFe 1
2O19
Ent
ropy
Pro
duct
ion:
Upp
er s
hift
ofth
e cu
rve:
di
ssip
atio
nof
ener
gy
Rev
ersi
ble
MC
E
= 0.
205
MJ
m-3
ii
eT
sTd
sTd
s
Dis
sipa
ted
ener
gyin
a c
lose
dhy
ster
esis
loop
:
Are
a of
mag
netic
satu
ratio
nhy
ster
esis
loop
:
0H
dM=
0.20
9 M
J m
-3
31/0
10/0
8L.
Giu
dici
Del
ft da
ys o
n M
agne
toca
loric
sA
ctiv
em
easu
rem
ents
Gd 5
Si 2.
09G
e 1.9
1T=
288K
Cou
pled
mag
neto
stru
ctur
altra
nsiti
on:
FM o
rthor
ombi
cto
PM
mon
oclin
icst
ruct
ure
-s e
asfu
nctio
nof
mag
netic
field
0Hm
ax=2
T
Ent
ropy
chan
geas
soci
ated
tola
tent
heat
ofth
e fir
st o
rder
phas
etra
nsiti
on:
hyst
eres
is
Smal
lent
ropy
prod
uctio
n
Sm
allp
ositi
ve s
hift
ofes
curv
e
Onl
y1%
ofth
e m
axim
umen
tropy
chan
ge
31/0
10/0
8L.
Giu
dici
Del
ft da
ys o
n M
agne
toca
loric
s
Effe
cts
ofhy
ster
esis
in N
iMnG
aan
d N
iMnS
n
GM
CE
: firs
t ord
er a
nd s
econ
d or
der t
rans
ition
sup
erim
pose
d
Hig
h en
thal
py o
f tra
nsfo
rmat
ion:
pro
mis
ing
mat
eria
ls
His
tory
dep
ende
nce
of
S(
H;T
): di
rect
mea
sure
men
ts
31/0
10/0
8L.
Giu
dici
Del
ft da
ys o
n M
agne
toca
loric
s
Exp
erim
enta
lmea
sure
men
tsN
i 55M
n 20G
a 25
sing
le c
ryst
al
T c=
312.
6 K
A
p=31
4 K
M
p=3
02 K
Firs
t ord
eren
doth
erm
ictra
nsiti
onpe
aksu
perim
pose
dto
Tcdu
ring
heat
ing
Hys
tere
sis
in fi
rst o
rder
trans
ition
T
290
295
300
305
310
315
320
325
330
0
500
1000
1500
2000
2500
3000
3500
Ap
cp (J/kgK)
T(K
)M
pT c
Aus
teni
teM
arte
nsite A
p-M
p12
K
Mag
netiz
atio
nm
easu
rem
ents
DSC
mea
sure
men
ts
Ferr
o-
Ap
Para
-
C.P
.Sas
soet
al.,
JAP
103
(200
8)
31/1
0/08
L.G
iudi
ci
Del
ft da
ys o
n M
agne
toca
loric
s
Af
time
time
T b
Mf
Ms
As
H
Pro
cess
A -
Fiel
d ap
plic
atio
nP
roce
ss B
-Fi
eld
rem
oval
050
100
150
200
250
300
-2-1012345
0H (T)
q (mW)
time
(s)
hea
t flu
x m
easu
red
at 3
09.9
K
0.0
0.5
1.0
1.5
2.0
mag
netic
fiel
d
His
tory
dep
ende
nce
of
S(
H;T
)
31/1
0/08
L.G
iudi
ci
Del
ft da
ys o
n M
agne
toca
loric
s
AU
STE
NIT
EM
AR
TEN
SIT
E
DO
UB
LE-W
ELL
E
NE
RG
Y P
OTE
NTI
AL
OR
DE
R P
AR
AM
ETE
R
Hea
ting
with
fiel
d
+
Fiel
d re
leas
ed
Hea
ting
with
out
field +
Fiel
d ap
plic
atio
n
Pro
cess
AP
roce
ss B
Qua
litat
ive
expl
anat
ion
ofhy
ster
esis
effe
cts
Ene
rgy
pote
ntia
lcan
be
dist
orte
dby
tem
perta
ure
and
mag
netic
field
Whe
non
em
inim
um b
ecom
esun
stab
leth
e tra
nsiti
onoc
curs
Dire
ctM
CE
: A) H
sta
biliz
esm
arte
nsite
, M-A
tran
sitio
nun
favo
rabl
eB
) H re
mov
ed: M
-A tr
ansi
tion
favo
rabl
e
31/1
0/08
L.G
iudi
ci
Del
ft da
ys o
n M
agne
toca
loric
s
Dire
ct m
easu
rem
ents
of e
xcha
nged
Ent
ropy
Diff
eren
tpre
para
tion
hist
orie
s
A: S
tarti
ngfro
mT<
Mf
T is
incr
ease
dw
ithH
=0 u
p to
T1Th
en0H
=2T
isap
plie
dan
d S
(H1T
1) is
mea
sure
d
B: S
tarti
ngfro
mT<
Mf
T is
incr
ease
dw
ith0H
=2T
up to
T 1 th
enfie
ldis
decr
ease
dto
0an
d S
(H1T
1) is
mea
sure
d
A) H
yste
resi
s of
Pha
seTr
ansi
tion
H p
rom
otes
mar
tens
ite
S is
decr
easi
ngS
Am
ax=
-4.4
J k
g-1K
-1
B):
H s
tabi
lizes
mar
tens
iteR
emov
ing
H a
nd ic
reas
ing
T
Tota
l ent
ropy
chan
geas
soci
ated
tom
agne
tost
ruct
ural
trans
ition
SB
max
=24
J kg
-1K
-1
300
305
310
315
320
325
330
335
-50510152025
s (J/kgK)
T (
K)
B:
Fie
ld R
emov
al -
0H
: 2T
-0T
24 J
kg-1
K-1
Diff
eren
tres
ults
!C
.P.S
asso
etal
., JA
P 1
03 (2
008)
L.G
iudi
ci
Dire
ct m
easu
rem
ents
of e
xcha
nged
Ent
ropy
Max
wel
l R
elat
ions
: S=
40 J
/kg
K
0H=2
T
310
311
312
313
314
315
316
02040
Ni 55
.4M
n 20.0G
a 24.6
2T
-S J/kgK
T (K
)
Isot
herm
alS
: 24
J /k
g K
S e
valu
ated
byM
axw
ell r
elat
ions
290
295
300
305
310
315
320
325
330
0
500
1000
1500
2000
2500
3000
3500
As
Ms
Mf
Ap
Af
cp (J/kgK)
T(K
)
Mp
S e
valu
ated
byD
SC m
easu
rem
ents
0H=0
T: 2
6 J/
Kg
K0H
=2T
: 24
J/K
g K
M.P
asqu
ale
etal
., P
RB
72
(200
5)
Am
esLa
bora
tory
(T.L
ogra
sso,
D.S
chla
gel)
Ann
eale
dat
900
°C fo
r72
hour
s
Ni 50
Mn 3
7Sn 1
3po
lycr
ysta
lline
sam
ple
225
250
275
300
325
350
375
400
-2-10123Power (mW)
T (
K)Ni 2M
nS
n10
K/m
inE
nd
oth
erm
ic d
ow
n
Co
olin
g
He
atin
g
TC
DSC
cur
ve
T cA=
315
K
Hys
tere
sis
of15
Kin
1st
orde
rtra
nsiti
onT
Hea
tCap
acity
CP=
430
J/ k
g K
|S|
= |-
H/T
|= 3
5 J/
Kg
K
T MA
s=
307
K
T MA
p=31
4 K
T MA
f=31
7 K
T AM
s=
301
K
T AM
p=2
98 K
T MA
f=29
3 K
010
020
030
040
050
00.
00
0.01
0.02
0.03
0.04
M (emu/mg)
T (K
)
0H=0
.9 T
TcM
Ferro
mag
netic
Aus
teni
te
Par
amag
netic
mar
tens
ite
Para
mag
netic
aust
enite
Ferro
mag
netic
mar
tens
ite
Mag
netiz
atio
nm
easu
rem
ents
(hea
ting)
Mag
neto
-Stru
ctur
al p
hase
tran
sitio
n at
room
tem
pera
ture
:
From
a m
arte
nsite
(M) p
hase
with
low
er m
agne
tizat
ion
to a
n au
sten
ite (A
) pha
se w
ithhi
gher
mag
netiz
atio
n.0
HT
TMHS
Inve
rse
MC
E:M
.Pas
qual
eet
al. A
PL
91 (2
007)
Del
ft da
ys o
n M
agne
toca
loric
s
Dire
ctm
easu
rem
ents
ofex
chan
ged
Ent
ropy
, 0H
=2T
A) b
oth
posi
tive
and
nega
tive
SA(H
)Tar
e m
easu
red
asso
ciat
edto
the
mag
netic
and
stru
ctur
altra
nsiti
onB
) onl
yne
gativ
e S
B(H
)T is
mea
sure
d,c
lose
toT c
, as
soci
ated
toth
e m
agne
tictra
nsiti
on
SA(H
) T:s
ampl
eT
was
incr
ease
d up
to a
targ
et v
alue
, the
n H
was
app
lied;
ea
ch
SA(
H) T
poin
t mea
sure
d af
ter
zero
fiel
d co
olin
g in
ord
er to
hav
e th
e sa
me
initi
al c
ondi
tions
.
SB(H
) T: H
was
app
lied
at lo
w T
,th
e sa
mpl
e w
as h
eate
d,
once
the
targ
et T
was
reac
hed
H w
as re
mov
ed.
Del
ft da
ys o
n M
agne
toca
loric
s
A)
Hea
ting
with
outf
ield
M-A
tran
sitio
nis
occu
ring
Fiel
dap
plic
atio
npr
omot
esth
e gr
owth
offe
rrom
agne
ticau
sten
iteph
ase,
(M
-A tr
ansi
tion)
SA(
H)T
> 0
IN
VE
RS
E M
agne
toca
loric
Effe
ct
B)
Hea
ting
with
field
M-A
tran
sitio
nis
occu
ring
Fiel
dre
mov
alsh
ould
prom
ote
the
para
mag
netic
mar
tens
ite p
hase
,w
ithlo
wer
entro
py, (
A-M
tran
sitio
n),
lead
ing
toS B
(H)T
> 0
bu
tthe
ther
mal
hyst
eres
is in
the
phas
etra
nsiti
onhi
nder
sth
e re
vers
e au
sten
iteto
mar
tens
ite p
hase
trans
ition
.N
O In
vers
e M
agne
toca
loric
effe
ctis
mea
sure
d
AU
STE
NIT
EM
AR
TEN
SIT
E
DO
UB
LE-W
ELL
E
NE
RG
Y P
OTE
NTI
AL
OR
DE
R P
AR
AM
ETE
R
Hea
ting
with
fiel
d
+
Fiel
d re
leas
ed
Hea
ting
with
out
field +
Fiel
d ap
plic
atio
n
Pro
cess
AP
roce
ss B
Qua
litat
ive
expl
anat
ion
ofhy
ster
esis
effe
cts
31/1
0/08
L.G
iudi
ci
Adi
abat
icTe
mpe
ratu
re C
hang
e:
T ad
= -0
.9 K
0H
=7T
T =
305
K
T ad
= -0
.3 K
0H
=2T
T =
305
K
Isot
herm
al e
ntro
py c
hang
e:
SA=
1.5
J kg
-1K
-10H
=2T
T=3
06 K
|S
|= |-
H/T
|= 3
5 J/
Kg
K
0H=0
T
DS
C m
easu
rem
ents
:
0
0.14
/p
AK
TH
T. K
renk
eet
al. N
atur
e M
at.
4,45
0, (2
005)
S=7
J/kg
K
0H=2
T
Unk
now
nhe
attre
atm
ent
Dire
ctS
and
T a
dm
easu
rem
ents
Max
wel
lR
elat
ions
:
Con
clus
ion
Peltie
r cel
l sam
ple
cera
mic
laye
rs
copp
er b
lock
s
vacu
um tu
be
T b
T s
sim
ple
setu
pP
eltie
rcel
ls
actu
ator
and
sens
orFu
rther
deve
lopm
ents
field
sup
to7T
, cry
osta
t
dire
ct m
easu
rem
ento
f en
tropy
chan
gem
easu
rem
ents
of m
agne
toca
loric
mat
eria
lsan
d m
agne
ticm
ater
ials
with
hyst
eres
is
test
mea
sure
men
tof G
dsh
owed
good
resu
lts
Hys
tere
sis
is im
porta
nt fo
r the
co
olin
g pe
rform
ance
s of
gia
nt
mag
neto
calo
ricm
ater
ials
.
Tim
e hi
stor
y of
H a
nd T
mus
t be
care
fully
con
trolle
d in
ord
er to
co
mpa
re m
agne
toca
loric
prop
ertie
s of
the
mat
eria
ls.
Pel
tierC
ells
Cal
orim
eter
NiM
nGa
NiM
nSn
31/1
0/08
L.G
iudi
ci
Del
ft da
ys o
n M
agne
toca
loric
s
31/1
0/08
L.G
iudi
ci
Del
ft da
ys o
n M
agne
toca
loric
s
31/1
0/08
L.G
iudi
ci
Del
ft da
ys o
n M
agne
toca
loric
s
Pel
tier
Effe
ctiv
eco
effic
ient
s
(4)
(3)
= to
tal s
eebe
ckco
effic
ient
R=
tota
l ele
ctric
resi
stan
ce=T
Pel
tier
coef
ficie
ntK
=th
erm
alco
nduc
tanc
eof
the
colu
mns
T=ab
solu
tete
mpe
ratu
re
Kp=
tota
l the
rmal
cond
ucta
nce
K=t
herm
alco
nduc
tanc
eof
the
colu
mns
Kl=
ther
mal
cond
ucta
nce
ofth
e 2
laye
rsR
p=ef
fect
ive
resi
stan
cep=
effe
ctiv
eP
eltie
rcoe
ffici
ent
Ep=
effe
ctiv
ese
ebec
kco
effic
ient
V.B
asso
etal
. Rev
.Sci
.Inst
rum
. 79,
063
907,
(200
8)
