Pressure effects on the transport properties of Ln2−xCexCuO4(Ln=Pr, Nd, Sm, Gd) single crystals

Physica C 185-189

(1991) 1 3 2 5 - 1 3 2 6

North-Holland

ON THE TRANSPORT P R O P E R T I E S

P R E S S U R E EFFECTS CRYSTALS

OF Lna-xCexCuO4(Ln=Pr. Nd,Sm.Gd) SINGLE

Aklyukl MATSUSHITA. Shinya UJI and Takehiko MATSUMOTO National Research I n s t i t u t e for Metals, Tokyo. JAPAN.

2-3-12 Nakameguro, Meguro-ku.

We m e a s u r e d t h e r e s i s t i v i t i e s o f L n = - x C e x C u O 4 ( L n = P r , Nd, Sm, Gd) s i n g l e c r y s t a l s under quasihydrostatic pressures up t o 1.6 (~Pa. I~educed L n 2 - x C e x e u 0 4 , Ln=Nd, Sm showed s u p e r c o n d u c t i v i t y w i t h Tc=I4K and IOK respectively, dTe/dP a t P--O was - 0 . 2 K / G P a f o r Ln=Nd a n d - O . 0 7 K / G P a f o r Ln=Sm. A s - g r o w n Gdl.g=Ceo.osCu04 showed an a n o m a l y of r e s i s t i v i t y below 13 K ~ h i c h i s i n d u c e d by m a g n e t i c transit i o n . We a l s o i n v e s t i g a t e d t h e p r e s s u r e e f f e c t s on t h e s e b e h a v i o r s in normal s t a t e ,

1.

piston-cylinder

INr~OOUCTION After

the discovery

superconductors

of

electron

Nd2-xCexCu041,

several

s u r e r e s e a r c h e s 2,3 have r e v e a l e d of h i g h - T c

superconductors

d e p e n d e n c e of d T c / d P .

pendence

was

doped h i g h - T o of

high

properties

of

because

series

of m a t e r i a l s

where

the

fected

by g r a i n

single

on

the

t h e normal

partly

report

different

on

most o f

on i n t e r e s t i n g

However.

are

in t h e n o r m a l

de-

state

for

the

Fig.

1 shows

clear, in t h i s

af-

latter at

sample

4.2ff b u t

temperature inflection

for

were grown u s i n g

sures.

obtained method

a CuO-based

semiconducting (as-grown

were a n n e a l e d

The Ce c o n c e n t r a t i o n determined

single

samples).

at 890~ of

flux

method 5-

crystals

Some s i n g l e

with

We this

crystals

in an Ar ( r e d u c e d s a m p l e s ) . the

single

crystals

were

Electrical measured with

resistivity a De f o u r - l e a d

under

pressure

was

method u s i n g a Cu-Be

0 9 2 1 4 5 3 4 / 9 1 / $ 0 3 . 5 0 © 1991 - Elsevier Science Publishers B.V.

the

N d l . 8 3 C e o . 17CuO 4. the

transition

~as n o t

observed.

TI,~ even

due

to

Pressure

The v a r i a t i o n

is determined

by t h e o n s e t

Ndl.83Ceo. 17CuO4 and by a p o i n t of

in t h e t r a n s i t i o n values

obtained

the

for

Sml. 83Ceo. 17CuO4.

using

these

criteria

In t h i s

resistivity

single

of

crystals

system a r e s i s t i v i t y

at

as-grown three

pres-

anomaly i s o b -

s e r v e d below 13K. This anomaly i s c o n s i d e r e d to be induced by a m a g n e t i c t r a n s i t i o n al. 6 have

recently

single-crystal served

temperature

between

R)

of

trapolated

is

and ~ 2 0 K .

closely

we e x t r a c t e d

resistivity

of

The ob-

proportional

to

t h e anomaly p a r t (

by s u b t r a c t i n g

log T d e p e n d e n c e .

All fights reserved.

Thompson et

d e p e n d e n c e of t h e r e s i s t i v i t y

15 and 80K

the

since

reported magnetic ordering

Gd2CuO4 at 6 . 5 [

log T. T h e r e f o r e .

u s i n g a EPMA.

on

of 7c f o r

snow z e r o r e s i s t i v i t y of

pressure

Fig. 2 shows

crystals

pressure

in t h e s e samples.

G d l . 9 2 C e . o8Cu04

single

of

f o r Tc were - 0 . 2 K / G P a and -O.07K/GPa, r e s p e c t i v e l y .

f o u n d by Uji 4

2. EXPERIMENTAL

not

pressure

The d T c / d P

samples w i t h

and f o r

did

little

on I c f o r r e d u c e d

L n 2 _ x C e x e u O 4 ( L n = P r , NdoSm,Gd)

by

t e m p e r a t u r e of Pb.

in the v i c i n i t y

broade~in~

the applied moved T c ' s of Tc w i t h

resistivity

effect

resistivity

we w i l l

paper,

as-grown

transition

the

S m l . 8 3 C e o . 17Cu04

of Ln2_xCexCu04 w i t h Ln=Nd. Sm and

Ln=Pr, Gd which were r e c e n t l y

plane(ab-plane). were c a l i b r a t e d

3. RESULTS AND DISCUSSION

the e f f e c t

is s t r o n g l y

b e h a v i o r s of e l e c t r i c a l

to the basal

low t e m p e r a t u r e s

transport not yet

In t h i s

effects

at

electrical

experiments

resistivitiy

pressure

crystals

pressure

from t h a t of h o l e

state

boundaries.

Pressures

The measurement c u r -

negative

intrinsic

the

r e n t was p a r a l l e l

the superconducting

series

were p e r f o r m e d on p o l y c r y s t a l s

electrical

the

this

This

superconductors.

pressure

that

high-To

high pres-

h a s a z e r o or

pressure

greatly

doped

clamp cell.

The

inset

this

ex-

sho~s t h e

A. Matsushita et aL / Transportproperties of Lnz.~Ce~CuO4 (Ln =Pr,Nd,$m,Gd)

1326

10

30

Temperature (K) 20 30 ~

r,,,dtgzCe.oaCuO4

50

Prt~iCe.~Cu04

25 . . . . . . . . . 5

e,~TCuo4

0,8

k ~3

-,i

2O

~0.~

:

aKc

,.

i

l~c_'.

_ .~'X" x

""

/Ndts3Ce.~./Cu~

nr •

~

o

J

io

z'o

Temperature (K)

~o

of

Each of

two main peaks. is below that.

these has small

over which A R is

lb

One

In the

can be ob-

temperature range

independent of temperature.

pressure

'

o b t a i n e d in t h i s

peak above 61( two components

of

t

02

GPa

ts

GP%..............

16O

26o

~05

~o"~6o

-j~

'3oo

on th e p a r t

of

The

the anomaly

Fig. 3, Pressure dependence of e l e c t r i c a l r e s i s t i v i t y and the magnitude of resistivity r e d u c t i o n n o r m a l i z e d by t h e resistivity at 0 GPa in asgrown P r l . 91Ce.09CuO4 s i n g l e crystal.

2501( in a d d i t i o n

to

the minimum.

The maximum is

not observed in the o t h e r m a t e r i a l s , the maximum variation

of

is not ex p l ai n ed yet. the r e s i s t i v i t y

large(more than 10~ at (R(P)-R(O))/R(O)

The o r i g i n of The f r a c t i o n a l

with

pressure

The v a r i a t i o n

below 1001( is p o s s i b l y caused

above 6K is to i n c r e a s e the width of each of i t s

by a change in the thermal a c t i v a t i o n

components and to d e c r e a s e

pressure

each component.

th e m a g n i t u d e of the

The m a g n e t i c

transition

tempera-

ture at 13K i n c r e a s e s with i n c r e a s i n g pressue. F i g . 3 shows resistivity crystal

the

pressure

d e p e n d e n c e of the

of an as-grown Prl. 85Ce0.15CuO 4 s i n g l e

(top)

at higher t e m p e r a t u r e s

the

energy with

in the s e m i c o n d u c t o r - l i k e s t a t e

to the r e s i s t i v i t y

is

1.6 GPa) and shows a r e l a -

t i v e l y week t e m p e r a t u r e dependence. of

see

Temperature(K)

Fig. 2. P r e s s u r e dependence of electrical resistivity of asgrown Gdl. 92Ceo. o8CuO 4 s i n g l e crystal. The i n s e t shows the t e m p e r a t u r e v a r i a t i o n of the anomalus p a r t o f t h e r e s i s tivity with i n c r e a s i n g p r e s sure.

the r e s i s t i v i t y

is above 61( and the o t h e r

effect

!

oi

Temperature (K)

way. The anomaly c o n s i s t s o f

served,

Temperature~K)

/\ \ 3 < o ,

"Z

Fig. 1. P r e s s u r e dependence of resistivities in the v i c i n i t y of s u p e r c o n d u c t i n g t r a n s i t i o n in r e d u c e d Sml. 83Ce0.17CuO 4 single crystal and r e d u c e d Ndl. 83Ceo. 17CuO 4 s y n g l e c r y s tal.

larger

Tmax I

g, - . 1 0

,b

anomaly p a r t

~

,x,

....

--,'N\ \ / ° 1o

0.2

~n.. zo

"~

c ~.-,~ ~.~ "~

\ i ~i

a: 0.4

n.-

0 GPa

0.7

-

is considered to be r e l a t e d

maximum. However.

large decrease

of

and that

the cause of

the r e s i s t i v i t y

with

i n-

c r e a s i n g p r e s s u r e is not yet now.

and the magnitude of the r e s i s t i v i t y

reduction with p r e s s u r e n o r m a l i z e d by the r e s i s -

REFERENCE

tivity

1. Y. Tokura et al,, ~ature (London)337(1989)345. 2. C. Yurayama e t a ] . , Nature 339(1989)293. 3. J. Beil]e e t a ] , , Solid State Commun.

at

P=0

(bottom).

semiconductor-like metallic-like

below

~80K.

but

at higher temperatures.

minimum of r e s i s t i v i t y two r e g i o n s . resistivity

The r e s i s t i v i t y

This in

is

to

Therefore a

a common f e a t u r e

t h e as-grown

at

turns

appears at Tmi n between the

crystals.

Ln2-xCexCuO,t(Ln=Pr, Gd) c r y s t a l s the r e s i s t i v i t y

is

a higher

of the However,

show a maximum of

temporature

Tma x

77(1991)141. 4. S. Uji. p r i v a t e communication. 5. S. g j i and H. Aoki, 6. D.J.Thompson et a l . ,

Physica B 165&166(1990)1537. Phys. Rev. B39(1989).6660.