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Magnetostriction and thermal expansion of high Tc magnetic superconductors REBa2Cu3O7−x (RE = Eu, Sm, Gd, Dy, Ho, Er, TmandY) Gd, Dy, Ho, Er, Tm and Y)
612
Journal of Magnetism and Magnetic Materials 76 & 77 (1988) 612-614 North-Holland. Amsterdam
MAGNETOSTRICTION
AND THERMAL
EXPANSION
OF HIGH
T,. M A G N E T I C
S U P E R C O N D U C T O R S REBazCu307_ ~ (RE = Eu, Sm, Gd, Dy, Ho, Er, Tm and Y) A. D E L M O R A L +, M . R . I B A R R A +, J.I. A R N A U D A S +, P.A. A L G A R A B E L C. M A R Q U I N A +, E. M O R A N *~ a n d M . A . A L A R I O =
÷
Depto. Fisica de la Materia Condensada and ICMA, Universidad de Zaragoza ('SIC, 50009 Zaragoza. Spain # Depto. Qu~rniea lnorggmica, Facultad de Ciencias, Universidad Cornplutense, 28040 Madrid, Spain
Thermal expansion and magnetostriction measurements for REBa2Cu30 v ~ superconductors are reported, up to 2.4 T and down to 3.8 K. Anisotropic striction is negligible, except for Dy and Ho compounds where is of single-ion origin. Volume striction displays similar order of magnitude and thermal variation, and it is weak (except for Dy compound) pointing to a "host" diamagnetic lattice origin.
1. Introduction
R E m a g n e t i c ions d o e s n o t d e s t r o y s u p e r c o n d u c tivity, T~ r e m a i n i n g at 92 93 K. T h i s is so ina s m u c h t h a t for R E = Dy, H o a n d E r the s y s t e m s s e e m to o r d e r a n t i f e r r o m a g n e t i c a l l y at T N < 1 K. It was s u g g e s t e d t h a t the d e n s i t y o f C o o p e r pairs is small at the R E sites, in a g r e e m e n t w i t h the a s s u m p t i o n t h a t s u p e r c o n d u c t i v i t y is r e s t r i c t e d to C u - O layers [2,3]. P r e v i o u s m e a s u r e m e n t s [1 3]
T h e m a g n e t i c [1-4], t h e r m a l [5,6], t r a n s p o r t [ 7 - 9 ] a n d elastic [10] p r o p e r t i e s of the H T C s u p e r conductors (HTCS) REBazCu307_,, ( R E = rare e a r t h ) h a v e b e e n t h o r o u g h l y s t u d i e d a f t e r t h e ann o u n c e m e n t o f H T C s u p e r c o n d u c t i v i t y in t h o s e m a t e r i a l s by W u et al. [11]. S u b s t i t u t i o n of Y by
3
xlO-6
x 10-3 I
Smc~ Y • Dy • H0 ° Gd • Eu o Tm •
_..J _.J
<1 E2 ._o
k
eD(K)
0.7
347
° nn
391
0.625 0.59
•
334 323 363 360 345
0.8 0.78 0.683
tt~ rI:1 ¢-~ x
o m o • • D ,~,l, • e a I~N&E) B I • • ,,',
o n •
i,".% I
c~ ~
o u • ra ~
15
•
•
-10 ~ Ill. . - , _
E
~
° • ~ ~ @
o *
¢-
8
1
.,,', -5
• 0
i,ll ! }" REao2Cu3O7-x I
I
100
200
TEMPERATURE
30 0
(K)
Fig. 1. Thermal expansion, A I / I , and th.e. coefficient, a, for REBa2CuzOv ~ superconductors, k is the quotient between the Y and RE compound thermal expansions. 0304-8853/88/$03.50
© E l s e v i e r S c i e n c e P u b l i s h e r s B.V.
A. del Moral et al. / H T C magnetic superconductors magnetostriction
indicate that the magnetic response of such materials is independent of superconductivity for fields below = 7 T, susceptibility below T~ showing Curie-Weiss behaviour, although a diamagnetic effect is observed below -- 2 T (e.g. in RE = Er) at low temperatures [3]. Previous thermal expansion (th.e.) measurements on YBa2Cu307_ ~ [12,13] do not show any anomaly at T~ and magnetostriction measurements indicate that it is weak ( = 10 - 6 at 7 K and 0.8 T), as in non-magnetic superconductors [13,14]. We present here the first systematic th.e. and magnetostriction measurements, parallel (XlI) and perpendicular (X±) to the magnetic field (up to 2.4 T) performed on REBa2Cu3OT_~, together with a preliminary interpretation.
2. Experimental results and discussion
613
xlO
'
,~
H:245T
~20
~0~ l
2O •
l
2~0
10
~ 30
t
40
l
50
T(K)
Fig. 2. Thermal variation of anisotropic magnetostriction, ?~t, for REBazCu3OT_ x (RE = Dy and Ho).
Th.e. allows the determination of Debye temperatures, OD; it can be shown that th.e. follows (for T << OD) the Griineisen from 2Xl/l-~ k o ( T 4 / 0 3 ) . Effectively all th.e. curves (fig. 1) collapse to the Y one, indicating likely the same phonon lattice origin, the one for the YBa2Cu 3 07_ x lattice, taking into account the differences in lattice cell masses. Taking as reference O D = 391 K for YBa2Cu3OT_x, from specific heat measurements [6], we have determined O D for the series (fig. 1 insert).
The samples were prepared by the usual route of these ceramics. Analysis using powder X-ray and electron microscopy were performed, as well as resistivity and magnetic susceptibility measurements, in order to characterize them as HTCS [4].
2.1. Thermal expansion Th.e. measurements were performed using the strain gauge technique, and in fig. 1 we show the thermal variation of AI/I (and, as an example, the th.e. coefficient for RE = Dy). N o phase transition anomaly is observed in a at Tc, within the experimental accuracy.
2.2. Magnetostriction For RE = Dy and Ho compounds the anisotropic magnetostriction, X t = Xll- X±, changes as
r
~ xlO~
1.50
3 I00
~E
~50
>o
~Dy
±
-T(K]
20
50
I
6O
Fig. 3. Volume magnetostriction, ~, thermal variation for the series REBa2Cu307_ x superconductors.
614
A. del Moral el aL / H T C magnetic superconductors rnagnetostriction
H 2, indicating a p a r a m a g n e t i c striction. A striking fact is that, except for H o a n d Dy, these systems behave (above 3.8 K) very isotropically, i.e. kll--k ± a n d )~t "~ 0. Instead k t is large for Dy a n d Ho c o m p o u n d s at 2.45 T (see thermal variation in fig. 2). A plot of k t vs. reduced m a g n e t i z a t i o n rn [2,3] gives a scaling m" with a near to 3, the e x p o n e n t for single-ion behaviour. Moreover X t ( D y ) / k , ( H o ) ~- 0.66 and the expected relation at 0 K for % J ( J - 1 / 2 ) (where a j is the Stevens coefficient) is 0.75, p o i n t i n g again to single-ion origin. We believe that such b e h a v i o u r is due to be m a i n l y observing the magnetostriction within the n o r m a l material inside the vortices. In the r e m a i n i n g comp o u n d s , where X, is negligible, we are likely at fields where the systems are still fully diamagnetic a n d the striction is relatively weak [13,14]. We should notice that no m e a s u r a b l e striction has been observed a r o u n d T~. In fig. 3 we show the thermal d e p e n d e n c e of the volume magnetostriction, ~0 = ~'11q- 2k • , at 2.4 T. All the c o m p o u n d s show (except T m a n d Er) a m a x i m u m in ~0. More noticeable is that, except for Dy, all ~0 are of the same order of m a g n i t u d e and vanish at similar temperatures. This strongly calls for a volume striction produced by the diamagnetic " h o s t lattice", with no intervention of the RE ions, i n a s m u c h that Y comp o u n d shows the same behaviour, a n d the same happens for Eu with J = 0. O n the other h a n d Dy
a n d Ho c o m p o u n d s show a w which r e m a i n s substantial up to high temperatures, p o i n t i n g to a single-ion origin as well. We are i n d e b t e d to the m e m b e r s of D p t o de Q u i m i c a Inorgfinica, Universidad C o m p l u t e n s e de Madrid: U. A m a d o r , M. Barahona, F. Fernfindez, J. Gonzfilez-Calbet, C. Otero, R. Sfiez-Puche and M. Vallet, a n d to J. G a r c i a of 1CMA, Universidad de Z a r a g o z a - C S I C for the p r e p a r a t i o n of the samples used in this research. We acknowledge also the financial support of the Spanish C I C Y T through grant 7 8 9 / 8 4 a n d the EEC HTS Project.
References [1] R.J. Cava et al., Phys. Rev. Len. 16 (1987) 1676. [2] J.R. Thompson et al., Phys. Rev. 11 36 (1987) 836. [3] P.A.J. de Groot et al., J. Phys. F 17 (1987) L185. [4] C. Rillo and F. Lera, private communication. [5] B.D. Dunlap et al., J. Magn. Magn. Mat. 68 (1987) L139. [6] H.P. van der Meulen et al., Physica C 152 (1988) 65. [7] F. Garcia Alvarado et al., Solid State Commun. [8] J.A. Veira et al., J. Phys. D 21 (1988) 378. [9] J. Garcla et al., J. Magn. Magn. Mat. 69 (1987) L225. [10] D.P. Almond et al., J. Phys. F 17 (1987) L221. [11] K.M. Wu et al., Phys. Rev. Lett. 58 (1987} 908. [12] V. Bayot et al., Solid State Commun 64 (1987) 327. [13] E. du Tremolet de Lacheisserie et al., J. Magn. Magn. Mat. 71 (1988) L125. [14] A. Br~indli,Phys. kondens. Mat. 11 (1970) 111.
Journal of Magnetism and Magnetic Materials 76 & 77 (1988) 612-614 North-Holland. Amsterdam
MAGNETOSTRICTION
AND THERMAL
EXPANSION
OF HIGH
T,. M A G N E T I C
S U P E R C O N D U C T O R S REBazCu307_ ~ (RE = Eu, Sm, Gd, Dy, Ho, Er, Tm and Y) A. D E L M O R A L +, M . R . I B A R R A +, J.I. A R N A U D A S +, P.A. A L G A R A B E L C. M A R Q U I N A +, E. M O R A N *~ a n d M . A . A L A R I O =
÷
Depto. Fisica de la Materia Condensada and ICMA, Universidad de Zaragoza ('SIC, 50009 Zaragoza. Spain # Depto. Qu~rniea lnorggmica, Facultad de Ciencias, Universidad Cornplutense, 28040 Madrid, Spain
Thermal expansion and magnetostriction measurements for REBa2Cu30 v ~ superconductors are reported, up to 2.4 T and down to 3.8 K. Anisotropic striction is negligible, except for Dy and Ho compounds where is of single-ion origin. Volume striction displays similar order of magnitude and thermal variation, and it is weak (except for Dy compound) pointing to a "host" diamagnetic lattice origin.
1. Introduction
R E m a g n e t i c ions d o e s n o t d e s t r o y s u p e r c o n d u c tivity, T~ r e m a i n i n g at 92 93 K. T h i s is so ina s m u c h t h a t for R E = Dy, H o a n d E r the s y s t e m s s e e m to o r d e r a n t i f e r r o m a g n e t i c a l l y at T N < 1 K. It was s u g g e s t e d t h a t the d e n s i t y o f C o o p e r pairs is small at the R E sites, in a g r e e m e n t w i t h the a s s u m p t i o n t h a t s u p e r c o n d u c t i v i t y is r e s t r i c t e d to C u - O layers [2,3]. P r e v i o u s m e a s u r e m e n t s [1 3]
T h e m a g n e t i c [1-4], t h e r m a l [5,6], t r a n s p o r t [ 7 - 9 ] a n d elastic [10] p r o p e r t i e s of the H T C s u p e r conductors (HTCS) REBazCu307_,, ( R E = rare e a r t h ) h a v e b e e n t h o r o u g h l y s t u d i e d a f t e r t h e ann o u n c e m e n t o f H T C s u p e r c o n d u c t i v i t y in t h o s e m a t e r i a l s by W u et al. [11]. S u b s t i t u t i o n of Y by
3
xlO-6
x 10-3 I
Smc~ Y • Dy • H0 ° Gd • Eu o Tm •
_..J _.J
<1 E2 ._o
k
eD(K)
0.7
347
° nn
391
0.625 0.59
•
334 323 363 360 345
0.8 0.78 0.683
tt~ rI:1 ¢-~ x
o m o • • D ,~,l, • e a I~N&E) B I • • ,,',
o n •
i,".% I
c~ ~
o u • ra ~
15
•
•
-10 ~ Ill. . - , _
E
~
° • ~ ~ @
o *
¢-
8
1
.,,', -5
• 0
i,ll ! }" REao2Cu3O7-x I
I
100
200
TEMPERATURE
30 0
(K)
Fig. 1. Thermal expansion, A I / I , and th.e. coefficient, a, for REBa2CuzOv ~ superconductors, k is the quotient between the Y and RE compound thermal expansions. 0304-8853/88/$03.50
© E l s e v i e r S c i e n c e P u b l i s h e r s B.V.
A. del Moral et al. / H T C magnetic superconductors magnetostriction
indicate that the magnetic response of such materials is independent of superconductivity for fields below = 7 T, susceptibility below T~ showing Curie-Weiss behaviour, although a diamagnetic effect is observed below -- 2 T (e.g. in RE = Er) at low temperatures [3]. Previous thermal expansion (th.e.) measurements on YBa2Cu307_ ~ [12,13] do not show any anomaly at T~ and magnetostriction measurements indicate that it is weak ( = 10 - 6 at 7 K and 0.8 T), as in non-magnetic superconductors [13,14]. We present here the first systematic th.e. and magnetostriction measurements, parallel (XlI) and perpendicular (X±) to the magnetic field (up to 2.4 T) performed on REBa2Cu3OT_~, together with a preliminary interpretation.
2. Experimental results and discussion
613
xlO
'
,~
H:245T
~20
~0~ l
2O •
l
2~0
10
~ 30
t
40
l
50
T(K)
Fig. 2. Thermal variation of anisotropic magnetostriction, ?~t, for REBazCu3OT_ x (RE = Dy and Ho).
Th.e. allows the determination of Debye temperatures, OD; it can be shown that th.e. follows (for T << OD) the Griineisen from 2Xl/l-~ k o ( T 4 / 0 3 ) . Effectively all th.e. curves (fig. 1) collapse to the Y one, indicating likely the same phonon lattice origin, the one for the YBa2Cu 3 07_ x lattice, taking into account the differences in lattice cell masses. Taking as reference O D = 391 K for YBa2Cu3OT_x, from specific heat measurements [6], we have determined O D for the series (fig. 1 insert).
The samples were prepared by the usual route of these ceramics. Analysis using powder X-ray and electron microscopy were performed, as well as resistivity and magnetic susceptibility measurements, in order to characterize them as HTCS [4].
2.1. Thermal expansion Th.e. measurements were performed using the strain gauge technique, and in fig. 1 we show the thermal variation of AI/I (and, as an example, the th.e. coefficient for RE = Dy). N o phase transition anomaly is observed in a at Tc, within the experimental accuracy.
2.2. Magnetostriction For RE = Dy and Ho compounds the anisotropic magnetostriction, X t = Xll- X±, changes as
r
~ xlO~
1.50
3 I00
~E
~50
>o
~Dy
±
-T(K]
20
50
I
6O
Fig. 3. Volume magnetostriction, ~, thermal variation for the series REBa2Cu307_ x superconductors.
614
A. del Moral el aL / H T C magnetic superconductors rnagnetostriction
H 2, indicating a p a r a m a g n e t i c striction. A striking fact is that, except for H o a n d Dy, these systems behave (above 3.8 K) very isotropically, i.e. kll--k ± a n d )~t "~ 0. Instead k t is large for Dy a n d Ho c o m p o u n d s at 2.45 T (see thermal variation in fig. 2). A plot of k t vs. reduced m a g n e t i z a t i o n rn [2,3] gives a scaling m" with a near to 3, the e x p o n e n t for single-ion behaviour. Moreover X t ( D y ) / k , ( H o ) ~- 0.66 and the expected relation at 0 K for % J ( J - 1 / 2 ) (where a j is the Stevens coefficient) is 0.75, p o i n t i n g again to single-ion origin. We believe that such b e h a v i o u r is due to be m a i n l y observing the magnetostriction within the n o r m a l material inside the vortices. In the r e m a i n i n g comp o u n d s , where X, is negligible, we are likely at fields where the systems are still fully diamagnetic a n d the striction is relatively weak [13,14]. We should notice that no m e a s u r a b l e striction has been observed a r o u n d T~. In fig. 3 we show the thermal d e p e n d e n c e of the volume magnetostriction, ~0 = ~'11q- 2k • , at 2.4 T. All the c o m p o u n d s show (except T m a n d Er) a m a x i m u m in ~0. More noticeable is that, except for Dy, all ~0 are of the same order of m a g n i t u d e and vanish at similar temperatures. This strongly calls for a volume striction produced by the diamagnetic " h o s t lattice", with no intervention of the RE ions, i n a s m u c h that Y comp o u n d shows the same behaviour, a n d the same happens for Eu with J = 0. O n the other h a n d Dy
a n d Ho c o m p o u n d s show a w which r e m a i n s substantial up to high temperatures, p o i n t i n g to a single-ion origin as well. We are i n d e b t e d to the m e m b e r s of D p t o de Q u i m i c a Inorgfinica, Universidad C o m p l u t e n s e de Madrid: U. A m a d o r , M. Barahona, F. Fernfindez, J. Gonzfilez-Calbet, C. Otero, R. Sfiez-Puche and M. Vallet, a n d to J. G a r c i a of 1CMA, Universidad de Z a r a g o z a - C S I C for the p r e p a r a t i o n of the samples used in this research. We acknowledge also the financial support of the Spanish C I C Y T through grant 7 8 9 / 8 4 a n d the EEC HTS Project.
References [1] R.J. Cava et al., Phys. Rev. Len. 16 (1987) 1676. [2] J.R. Thompson et al., Phys. Rev. 11 36 (1987) 836. [3] P.A.J. de Groot et al., J. Phys. F 17 (1987) L185. [4] C. Rillo and F. Lera, private communication. [5] B.D. Dunlap et al., J. Magn. Magn. Mat. 68 (1987) L139. [6] H.P. van der Meulen et al., Physica C 152 (1988) 65. [7] F. Garcia Alvarado et al., Solid State Commun. [8] J.A. Veira et al., J. Phys. D 21 (1988) 378. [9] J. Garcla et al., J. Magn. Magn. Mat. 69 (1987) L225. [10] D.P. Almond et al., J. Phys. F 17 (1987) L221. [11] K.M. Wu et al., Phys. Rev. Lett. 58 (1987} 908. [12] V. Bayot et al., Solid State Commun 64 (1987) 327. [13] E. du Tremolet de Lacheisserie et al., J. Magn. Magn. Mat. 71 (1988) L125. [14] A. Br~indli,Phys. kondens. Mat. 11 (1970) 111.