studiul relaxarii magnetizarii ireversibile in supraconductorii puternic dezordonati
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Studiul relaxarii magnetizarii ireversibile in supraconductorii puternic dezordonati
Ion Ivan
NATIONAL INSTITUTE OF MATERIALS PHYSICS BUCHAREST-MAGURELE
Atomistilor Str. 105 bis, P.O. Box MG-7, 077125 Magurele-Ilfov, Romania
Phone: +40(0)21 3690185, Fax: +40(0)21 3690177, email: frunza@infim.ro, http://www.infim.ro
Meissner effect
cTT
0B
cTT
Perfect conductor
0ρ
Magnetic fielddestroys s/c
cHH cHH 0
Ic Bc
Electric currentdestroys s/c
-Topirea retelei de vortexuri Abrikosov intr-un lichid de
vortexuri la Tm
-Centrii de fixare a vortexurilor sunt eficienti in cazul
solidului de vortexuri si practic ineficienti pentru un lichid
de vortexuri-Pentru un solid de vortexuri eficienta centrilor
de fixare(existenta unui densitati critice de curent finite)
se termina la linia de ireversibilitate, definita ca
linia in diagrama (H, T) deasupra careia nu exista
histerezis in curbele de magnetizare
T <Tm T >Tm
The drunken walk of vortices
Phys. Rev. Lett. 80, 2693
20
22 acTu Lthm Lindemann criterion
B
J
FL
fixarec fJ 0
Forta Lorentz care actioneaza pe unitatea de Forta Lorentz care actioneaza pe unitatea de lungime a vortexuluilungime a vortexului 0Jf
Vortex captat intr-un centru pining
* V. Dolocan, Supraconductibilitatea-Principii fizice si aplicatii,Ed.Univ.Bucuresti,1997.
MMM
MJ c
Materiale feromagnetice
HHMHB m
100
m 10
Supraconductori HM
1
0
yz J
x
B0
0nB
n – numarul de vortexuripe unitatea de suprafata
12
34
56
78
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
510
1520
2530
35 40
J c*107
(A
/cm
2)
T(K)
--- YBCO PLD--- YBCO SPUTTERING
-0.4
-0.2
0
0.2
0.4
-10 -5 0 5 10
T = 5, 10, 20, 30, 40, 50, 60, 70 K
0H (T)
m (
emu)
YBCO - PLD
MMM
Ll
dLl
MJ c
31
20
2
3312
2
103
mmRAd
emuM
cm
AJ irr
c
Ybco-LiCl neutron iradiated
I=0
I >0 U = U0 JBVx
UU = = UU00 (1 – (1 – JJ//JJCC))
Modelul Kim-AndersonModelul Kim-Anderson
Lege tip ArrheniusLege tip Arrhenius
,)/ln(1)()( 00
0
tt
U
TtJtJ
.)/ln(1)()( 00
0
tt
U
TtMtM
0.75
0.80
0.85
0.90
0.95
1.00
0 500 1000 1500 2000 2500
5K10K15K20K25K30K35K45K
time(s)
m/m
0
0.85
0.95
100 200 500 1000 2000
5K10K15K20K25K30K35K45K
time(s)
m/m
0
200
300
400
500
600
700
0 10 20 30 40 50
T(K)
U* (K
)
J < Jc J = Jc J > Jc
.)/ln(1)()( 00
0
tt
U
TtMtM
p
c t
t
U
pkTMtM
/1
0
ln10
]1)/)[(/(),,( p
cc JJpUJHTU
UU = = UU00 (1 – (1 –JJ//JJCC)) Kim-Anderson modelKim-Anderson model
Colective creep modelColective creep model
M
tT
S
TU
ln
ln*
)ln(
)ln(
t
MS
0* UU
0
* lnt
tpTUU c
0.005
0.01
0.02
0.05
0.1
100 200 500 1000 2000 5000
50
40
30
20
10
T (K)
H = 40 kOe
t (sec)
M
(em
u)
0
200
400
600
800
1000
1200
0 10 20 30 40 50 60 70 80
?
H = 40 kOe
T (K)
U0 (
K)
0
2
4
6
8
10
0 0.2 0.4 0.6 0.8 1.0
U = 1/J - 1
U0
J
U
)/ln(),,( JJUJHTU cc
- la tempratura de crossover M(t)=M(0)(t/t0)-s, S=KT/Uc
td
d
t
tTJJU cc ln
ln)/ln(0
Ttd
dJJJU
dJ
dcc
ln)]/ln([
Md
tdTUMJ c ln
ln
*U
*UU c
0,)(*
p
J
JUJU
p
ccppl
0,)(*
J
JUJU c
ceel
U * arata eficienta piningului la T=Tcr
-creep elastic
-creep plastic
)/ln(),,( JJUJHTU cc
M
tT
S
TU
ln
ln*
)ln(
)ln(
t
MS
rata de relaxare normalizata
15
25
35
45
0 5 10 15
T(K)
U* (
K)
0
* lnt
tTUU w
ceel
0
* lnt
tTpUU w
cppl
0
lntt
Tp
UUT
w
cecpcr
click
]1)/)[(/(),,( pcc JJpUJHTU
0,)(*
J
JJU c
0,)(*
p
J
JJU
p
c
-Creep elastic
-Creep plastic
Md
tdTU
ln
ln*
0
500
1000
1500
0 5 10 15
40 30 20
H = 10 kOe
T = 10 K
15
20
25
30
M (104 emu/cm
3)
U(J
) =
–T
[ln(
dM/d
t) –
C]
(K)
0
0.2
0.4
0.6
0.8
1.0
10 20 30 40
Uc
H (kOe)
, U
c (10
3 K)
dM/dt exp[U(J)/T], U(J) = – T[ln(dM/dt) C]
Maley technique
H = aT2,
a 1.2 104 kOe K2Strat Y-123 depus pe SrTiO3
0,)(*
p
J
JUJU
p
ccppl
0,)(*
J
JUJU c
ceel
0
400
800
1200
1600
0 20 40 60 80
T
cr
49
40
30
20
H = 10 kOe
T (K)
U*
(K)
0.005
0.01
0.02
0.05
0.1
100 200 500 1000 2000 5000
50
40
30
20
10
T (K)
H = 40 kOe
t (sec)
M
(em
u)
0
* lnt
tTUU w
ceel
0
* lnt
tTpUU w
cppl
0
0.1
0.2
0.3
0.4
0.5
0 10 20 30 40 50 60 70 80
49
4030
20
H = 10 kOe
T (K)
S
1D-APCs
c ax
is
Substrat MgO Buffer SrTiO3
Strat
YBCO
•Filmele au fost depuse prin PLD, pe un substrat MgO orientat (100) cu buffer SrTiO3 (STO) folosind un laser cu excimer Lambda Physik KrF (λ = 248 nm), avand o energie de 340 mJ/puls si o presiune partiala de oxigen de 200 mTorr.
nmd 5
nma 30
-diametru nano-rod BaZO3
-distanta medie intre doua nanorod-uri
ZrO2 – stabilizat cu Y2O3
5x106
107
2x107
5x107
108
0 10 20 30 40 50
T = 20 KYBCO
YBCO BZO
H (kOe)
J c (A
/cm
2 )
-3
-2
-1
0
80 82 84 86 88 90 92
YBCO BZOH = 10 Oe
Tc
T (K)
m (
10–3
em
u)
Pentru straturile cu centrii de fixare columnari se observa o cresterecu 100% a densitatii critice de curent, fata de straturile YBCO simple.Temperatura critica a fost obtinuta masurand m(T). Se observa o scadere nesemnificativa cu 4 0C pentru YBCO-BZO.
0
0.5
1.0
1.5
2.0
0 10 20 30 40 50 60 70 80 90
4030
20
10
H (kOe) = 49
T
cr
YBCO BZO
T (K)U
* =
T/S
(10
3 K)
0
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0 10 20 30 40 50 60 70 80 90
YBCO BZO
49
4030
2010
H (kOe)
T (K)
S =
–l
nM
/l
n(t)
0.1
1
10
2030
100 200 500 1000 2000 5000
75
70
605040302010
T (K)H = 10 kOe
t (s)
M
(104 e
mu/
cm3 )
Ep = Eel la T = Tcr
Eel H1/2
Tcr H1/2
5
10
20
50
30
40
60
40 50 60 70 80 90
YBCO BZO
H 1/T2
Tcr
(K)
H (
kOe)
100
200
500
1000
2000
2x10-8 5x10-8 10-7 2x10-7 5x10-7 10-6
YBCO BZO
~ 0.5
~ 1
H = 40 kOe
H = 10 kOe
1/J (cm2/A)
U*
(K)
0,)(*
p
J
JUJU
p
ccppl
0,)(*
J
JUJU c
ceel
Ep U(J) ~ Tln(tw/t0)
0
* lnt
tTUU w
ceel
20
30
40
50
60
0.6 0.8 1.0 1.2 1.4
YBCO YO
H = 49 kOe
YBCO
YBCO BZO
U*(Tcr
) (103 K)
Tcr (K
)
0
400
800
1200
1600
2000
0 0.2 0.4 0.6 0.8 1.0
Y4/Pr4
YBCO sputtered
YBCO
YBCO + BZOH = 20 kOe
T/Tc
U*
(K)
Pentru toate straturile YBCO, probele cu centrii de fixare columnari BZO, prezinta cel mare pinning
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