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