Anisotropy of the monodomain TmBa2Cu3O7−x single-crystal magnetic properties

PhysicaC 162-164(1989) 1633-1634 Nonh-HoDand

ANISOTROPY

OF THE

V.V.MOSHCHALKOV,

MONODOMAIN

TmBazCu3OT-x

SINGLE-CRYSTAL

V.S.BELOV,

V.I.VORONKOVA.

O.V.PETRENKO,

L a b o r a t o r y of H i g h - T o S u p e r c o n d u c t i v i t y , University, Moscow 117234, USSR.

Physics

MAGNETIC

Department,

PROPERTIES.

Moscow

State

The m a g n e t i z a t i o n M(H) of the m o n o d o m a i n T m B a 2 C u 3 O T - x s i n g l e c r y s t a l w a s m e a s u r e d at T = 4 . 2 K in o r i e n t a t i o n s of m a g n e t i c f i e l d H a l o n g a, b a n d c - c r y s t a l ' s axes. T h e l o w e r c r i t i c a l f i e l d s He, a n d c r i t i c a l c u r r e n t d e n s i t i e s Jc w e r e found.

The

anisotropy

conductor's perties 1,z .

electric

were

But

tropy

in the

density

of

kOe

twin

due

the

of a n i s o -

field

for all

orientations

with

tallographic

axes.

in

single -16)0 k

the m a g n e t i z a t i o n

monodomain

crystal

up

TmBazCu30~-x

to

mmw'""

ed

in t h e s e

technology samples

studies published

(Tml)

the c r y s -

: d

single

crystals

The

parallel

to the

the

la

low

tization

One

e

e •

•

was

(curve

N i),

b-axis

(N 3),

with

the

domain of b o t h

a flake-like

facet

of

1.4

the

disk mm

disk

in is

(ab)-plane. the

field

temperature of H

Tml I

dependence

(T=4.2K)

for

a-axis

respectively.

H

I

2

•

:.: .i.:.'..'.'2":

40,

10

~

~

~) U,'k0e

FIGURE 1 a) Hysteresis loops M vs H of the TmBa2Cu307-x re•nod•main s i n g l e crystal for the field's orientations with respect to a, b, c crystal axes at T = 4.2 K: I- H | c; 2- H I b, 3- H I

a.

b) The M(H) anisotropy in the (ab)plane for the Tml sample in an a p p r o p r i a t e scale.

magnec-axis

(N 2) a n d H The

21"

twin

shape

and

3

the

single

The

•

0

(Tc,89K)

(Tm2)

of

~m.

shows

M(H)

of

crystal

•

us-

by the

without

in t h i c k n e s s

diameter.

of

in 3 .

sample

= i00

0.i m m

Fig.

grown

second

dimensions

areas

of

the

a polydomain

average

were

region

boundaries;

crystals

Tc " 83 K h a d a 75~

with

monodomain

was

single

•°

M9

10-

TmBa2Cu3OT-x

m •

emu. T

field's

•

The

2

i• w • •l Il I l

to 50

magnetic

respect

00 0 mmO0 0 0 0

~'~t

pro-

A

to the h i g h

boundaries

studied

" ° °

intensively

no s t u d i e s

on magnetic

for

single

are

en•jM'-•

super-

magnetic

(ab)-plane

We

dependence

and

investigated

there

crystals.

of the h i g h - T o

I

M(H)

0921--4534/89/$03.50 © Elsevier Science Publishers B.V. (North-Holland)

anisotropy appropriate The

in the scale

anisotropy

(ab)-plane is g i v e n

in an

in Fig.

of the m a g n e t i z a t i o n

lb. in

1634

V.V. Moshchalkov et al. / Monodomain T m B a 2Cu j O z_ ~ single-crystal

the

field

applied

parallel

to

the

16:1

the

field

in

Nearly was

the

same

found

Tm2

for

single

current

AM

by

is

anisotropy

oxygen

Cu(1)

atoms.

observable

field ates

lower

at

slope Tml

M

the

perfect at

component} estimated

field's crystal

values

at

are

much Hcl's

crystal,

c,

where

we

D is

the : 1

)

~ 50

caused of to

the

Hot

monodomain current

from

the

= AM

/ d

tal

at

± c-axis) the

=

same

crystal. density

jc

was

relation:

no

were a

deviinitial

sample

thickness

in the

(ab)-plane

~ c-axis,

is

same

and

twin

such

to

as

be than

there oxygen more

twin

jc{Hl(ab)-

polydomain jc's (i)

Tm2

values

have

the

These

data

boundaries

pinning

crystals

crys-

jc(H|c-axis)

magnitude.

the

effective

seem

the

formula

of

single

kOe,

corresponding

that

centers

Tml

H=25

For

from

order

defects

a disk.

l*104A/cm 2 and

the

single

of

monodOmain

5*104A/cm 2 .

assume

respectively 4 . Here

are't

centers. exist

In the

some

vacancies,

effective

point which

pinning

boundaries.

the

T=4.2K, Nc{

Nab{(ab)-

the

fields

Hcl

260

and

Oe

disk

diameter

sample

(I),

* D for H

T=4.2K

plane} is

the

the

estimated

as

For

the For

the

Oe,

H |

the

is

the

same

factors and

d

for H

be

the

T=4.2K

the

jc

and

curves

Although the

corresponding single

1700

/ {HcI(H

is p r a c t i c a l l y

critical

the

H

fields

= 0.07,

for

d = 1/3

~

temperature

H U

that

the

= 0.87

Oe}

: 6.5

and

magnetization

as:

for

M of

there's

in

with

650

M vs H

of

respect

demagnetizing

respectively.

an

diamagnetism.

component}

270 Oe

the

to

vs H

linearity

the

plane

was

from

jc

critical the

crystal

c-axis

T=4.2K

range.

which

of

using

were

from

from

for

as

=

Oe}

The

( 1.4

anisotropy

i00

calculated

kOe

with

axis)

anisotropy

distributions

But

kOe.

(ab)-plane

I0

-

polydomain

value

seems

atoms

fields

The

In t h e

fields

anisotropic

20

model,

anisotropy

chain

defined

Bean

5:1.

large

magnetization

smaller

magnetic

magnetic

at

and

critical

traversed

the

much

This

the

The

jc

it

using

magnetizaton

kOe.

of

ordinary

in the

as

anisotropy

in

value

is

above

inductively

sample

found

plane

range

an

density

hysteresis

loop,

(ab)-

crystal.

determined

the

perpendicular

REFERENCES I. Y. I s i k a w a , A p p l . Phys.

K. M o r i e t . a l . , 27 (1988) 403.

Jap.

2.

W.J. al.,

Gallagher, T.K. W o r t h i n g t o n P h y s i c a 1 4 8 B (1987) 228.

3.

V.I. V o r o n k o v a , I.V. V o d o l a z s k a y a , V.K. J a n o v s k i y , Sverkhprovodimost. Fhisica, Khimiya, Tekhnologiya 2 (1989) 41.

4.

C.P. 250.

J.

at.

a and H J b, low c r i t i c a l f o r the

smaller

than

values

for

the

ratio

{Hcl(H

Tm2 the Tml ! c-

Bean,

Phys.

Rev.

Lett.

8 (1962)