- Email: [email protected]
A new magnetic superconductor Er2Fe3Si5
PflYSICA
Physica B 194-196 (1994) 1975-1976 North-Holland
A new
magnetic
superconductor
Er2FeaSi5
S. Noguchi and K. Okuda D e p a r t m e n t of Physics ~nd Electronics, University of Osaka Prefecture, Sakai, Osaka 593, J a p a n A new magnetic superconductor Er2Fe3Sis was found by electrical resistivity measurements down to 0.1 K. The zero resistivity was attained at T¢0 = 0.47 K below incommensurate and commensurate amtiferromagnetic transition at 2.8 and 2.4 K, respectively. The upper critica2 field H¢2 is determined from a midpoint of the resistive transition. The initiM slope of Hc2(T) at T¢ is obtained to be -1.9 kOe/K. Hc2(0) is estimated to be 1.3 kOe from the W H H curve fitting. The coherence length is estimated to be ~0 = 500 A.
The tetragonal ReFe3Sis compounds form an interesting isostructure of space group P 4 / m n c , with superconducting members ( R = Sc, Y, Lu ), antiferroma.gnetic members ( R = Gd, Tb, Dy, Ho, Er ), and a reentrant superconductor ( R = T m ) which shows the quenching of superconductivity on the antiferromagnetic ordering [1-5]. In the antiferrornagnetic members there has been no evidence of coexistence between magnetic order and superconductivity so far [3]. Recently, on the course to search for new ternary rare-earth compounds we observed an abrupt drop of resistance near 1 K in Er-Fe-Si multiphase sample including Er2Fe3Sis phase. So as to identify the superconducting phase, the resistivity measurement down to 0.1 K was ,:lone first in Er~Fe3Sis single phase in the present study. Sample of Er2Fe3Si5 was prepared by arc- melting the constituent metallic elements in a Ti- gettered high-purity argon atmosphere. The ingot was wrapped in a Ta foil, sealed under vacuum in a quartz tube, and then annealed successively at i000 °C for 4 days, 900 °C for 2 days, and
800 °C for 2 days. X - r a y powder diffraction pattern indicates the sample is almost a single phase with lattice parameters a = 10.39 + 0.01 ]~ and c = 5.429 4- 0.005 I which are in good agreement with the previous results [4]. The electriced resistivity was measured by a standard four terminal method in a temperature range from 0.t to 300 K using the 3He cryostat combined witk an adiabatic demagnetization cell. The t e m p e r a t u r e dependence of the resistivity nor-
e..l e., 0.5 e,,
[
I
i
i
I
t
i
i
r
200
300
TEMPERATURE(K/
Figure 1. Temperature dependence of the resistivity in Er2 Fea Sis. 0.08
J
2.aK
0.06
j2.8K
O~
OQ$Ot O
S
0.04 e,,
• 002
Er2Fe3Si s
* -#.
"
?~l/0.47K 2
4
15
8
l0
TEMPERATURE(K)
Figure 2. Details of R(T) at low temperatures in Er2FeaSis. A clear superconducting transition is observed below 1.3 K. Anomalies at 2.8 and 2.4 K are due to the incommensurate and commensurate antiferromagnetic transitions, respectively [4].
0921-4526/94/$07.00 © 1994 - Elsevier Science B.V. All rights reserved
SSDI 0921-4526(93)1620-2
i
10o
1976
[
,
;
r
T
~
1-
•
!
'
1.5
)
j
]
i
"~0kOe
i dHcs/dT=- 1.90kOe/K G=Tc)
O
i
"4
E "~
]
kd 0 (]2
O 5
m;
Er:Fe:,Sh
L/,/
4
t,
s
ill
0.93K !
10
H(kOe)
(THFVeS
Er-,Fe:,Si~
t 2
Figure 3.
o
(~5L
o
I 0
]
Typical examples of magneIoresis~ance Er2FesS s at, several lcmpera.tures.
realized by t h e value at r o o m t e m p e r a t u r e , pzvu = 254 # f b c m , is shown in Fig. 1. T h e resistivity decreases with decreasing t e m p , : r a t u r e , showing a positive c u r v a t u r e arou]ld 100-200 K, and therl reveeded art a b r u p t decrease: at 1 K. Det~dls at b w t e m p e r a t u r e s are shown in Fig. 2. T h e resistivity shows a s m ~ t p e a k at 2.8 K, a sharp d r o p at 2.4 K, ~nd then a b r u p t l y decreases agmn from 1.3 K down to 0.47 K where the resistivity b e c o m e s zero. A n o m a l i e s at 2.8 a~Ld 2.4 K c o r r e s p o n d to the i n c o m m e n s u r a t e and commc~s u r a t e a n t i f e r r o m a g n e t i c t r a n s i t i o n s , respectively, r e p o r t e d by M o o d e n b a u g h ef el ht the neutrcm diffraction meatsurements [4]. T h e s u p e r c o n d u c t ing t r a n s i t i o n is r a t h e r b r o a d as t}te width betw,;en 10 % and 90 % of the resistive t r a n s i t i o n is e s t i m a t e d to be AT~ = 0.67 K. T h e m i d p o i n t of resistive t r a n s i t i o n is 0.93 K. No evidence of r e e n t r a n t b e h a v i o r was observed down to 0.1 K. To d e t e r m i n e the t e m p e r a t u r e dependenc~ of the u p p e r critical field, He2, the rnagnetoresist a n c e m e a s u r e m e n t s of Er~FesSis were done at several t e m p e r a t u r e s . T h e m a g n e t i c field is applied up to 30 kOe parallel to curreitt dir~ctic,n. T r a n s i t i o n s to the n o r m a l s t a t e were. observed u nder fields up to 3 kOe ~s shown in Fig.3. Th~ He2 defined as a rcddpoint of resistive t r a n s i t i o n is obtained as ~ function of t e m p e r a t u r e ms shown lit Fig.4. The initial slope of Ho(T) at T~, (dH,~/dT)T,, is o b t a i n e d to b e - 1 . 9 k O e / K . T h e W H H t h e o r y [6] for the calculation of H~2(T) provides a good fit to the e x p e r i m e n t a l d a t a as drawr~ by a dotted line in Fig.4. T h e z e r o - t e m p e r a t u r e critical
{~1 0
I
I
!
0.5
t
t
I ~___
]
TEMPERATURE(K) Figure 4 Lg~(T) curve of Er~F{~3Sis The ff~ is determined from a midpoint of the resistive t r a n s i t i o n l)otted line is obtained from the WHIt fitting wi~h A. . . . ~ [q.
field He2(0) is e s t i m a t e d to be 1.3 kOe. Since tl~<~ value is considered as orbitaJ, critical field, the G L coherence length ~c0 is e s t i m a t e d to be (u = 500 k. []~ s u m m a r y , a new m a g n e t i c s u p e r c o n d u c t o r gr2FegSis was found. T h e zero resistive transition t e m p e r a t u r e is c,t,tained to be T~(, = 0.47 K below the i n c o m m e n s u r a t e anti c o m m e n s u r a t e a n t l f e r r o m a g n e t i c t r a n s i t i o n at 2.8 and 2.4 K, respectively. Dora the H~2(T) curve, (dHo/dT)>: and He2(0 ) are e s t i m a t e d to be -1.q k O e / K ~nd 1.3 kOe, respectively. T h e coherence length is ~.st i m a t e d to be ~0 = 500 It.
References 1. O1. Bodak, B.Ya. Kotur, V I . Yarovets and E.1. Gradyshevskii, Soy. Phys. Crystallogr. 22 (1977) 217. 2 H.F. Braun, Phys. L e t t 75A (1980) 38(;. 3. C.B. Vining and R N . Shetton, Phys. R e v B28 (198a) 2rv_3. 4 A.K. Moodenbaugh, D.E. Cox, C.B. Vinmg anti C.U. Segre, Phys. Rev. B29 (1984) 271 5. J. A. Gotaas, J. W. Lynn, R N. Shelton, P Klavins and H.F. Braun, P h y s Rev. BS6 (1987) 7277. 6 N. R. Werthamer, E. Helfand and P . C . Hohenberg, Phys. Rev. Lett. 52 (1966) 295
Physica B 194-196 (1994) 1975-1976 North-Holland
A new
magnetic
superconductor
Er2FeaSi5
S. Noguchi and K. Okuda D e p a r t m e n t of Physics ~nd Electronics, University of Osaka Prefecture, Sakai, Osaka 593, J a p a n A new magnetic superconductor Er2Fe3Sis was found by electrical resistivity measurements down to 0.1 K. The zero resistivity was attained at T¢0 = 0.47 K below incommensurate and commensurate amtiferromagnetic transition at 2.8 and 2.4 K, respectively. The upper critica2 field H¢2 is determined from a midpoint of the resistive transition. The initiM slope of Hc2(T) at T¢ is obtained to be -1.9 kOe/K. Hc2(0) is estimated to be 1.3 kOe from the W H H curve fitting. The coherence length is estimated to be ~0 = 500 A.
The tetragonal ReFe3Sis compounds form an interesting isostructure of space group P 4 / m n c , with superconducting members ( R = Sc, Y, Lu ), antiferroma.gnetic members ( R = Gd, Tb, Dy, Ho, Er ), and a reentrant superconductor ( R = T m ) which shows the quenching of superconductivity on the antiferromagnetic ordering [1-5]. In the antiferrornagnetic members there has been no evidence of coexistence between magnetic order and superconductivity so far [3]. Recently, on the course to search for new ternary rare-earth compounds we observed an abrupt drop of resistance near 1 K in Er-Fe-Si multiphase sample including Er2Fe3Sis phase. So as to identify the superconducting phase, the resistivity measurement down to 0.1 K was ,:lone first in Er~Fe3Sis single phase in the present study. Sample of Er2Fe3Si5 was prepared by arc- melting the constituent metallic elements in a Ti- gettered high-purity argon atmosphere. The ingot was wrapped in a Ta foil, sealed under vacuum in a quartz tube, and then annealed successively at i000 °C for 4 days, 900 °C for 2 days, and
800 °C for 2 days. X - r a y powder diffraction pattern indicates the sample is almost a single phase with lattice parameters a = 10.39 + 0.01 ]~ and c = 5.429 4- 0.005 I which are in good agreement with the previous results [4]. The electriced resistivity was measured by a standard four terminal method in a temperature range from 0.t to 300 K using the 3He cryostat combined witk an adiabatic demagnetization cell. The t e m p e r a t u r e dependence of the resistivity nor-
e..l e., 0.5 e,,
[
I
i
i
I
t
i
i
r
200
300
TEMPERATURE(K/
Figure 1. Temperature dependence of the resistivity in Er2 Fea Sis. 0.08
J
2.aK
0.06
j2.8K
O~
OQ$Ot O
S
0.04 e,,
• 002
Er2Fe3Si s
* -#.
"
?~l/0.47K 2
4
15
8
l0
TEMPERATURE(K)
Figure 2. Details of R(T) at low temperatures in Er2FeaSis. A clear superconducting transition is observed below 1.3 K. Anomalies at 2.8 and 2.4 K are due to the incommensurate and commensurate antiferromagnetic transitions, respectively [4].
0921-4526/94/$07.00 © 1994 - Elsevier Science B.V. All rights reserved
SSDI 0921-4526(93)1620-2
i
10o
1976
[
,
;
r
T
~
1-
•
!
'
1.5
)
j
]
i
"~0kOe
i dHcs/dT=- 1.90kOe/K G=Tc)
O
i
"4
E "~
]
kd 0 (]2
O 5
m;
Er:Fe:,Sh
L/,/
4
t,
s
ill
0.93K !
10
H(kOe)
(THFVeS
Er-,Fe:,Si~
t 2
Figure 3.
o
(~5L
o
I 0
]
Typical examples of magneIoresis~ance Er2FesS s at, several lcmpera.tures.
realized by t h e value at r o o m t e m p e r a t u r e , pzvu = 254 # f b c m , is shown in Fig. 1. T h e resistivity decreases with decreasing t e m p , : r a t u r e , showing a positive c u r v a t u r e arou]ld 100-200 K, and therl reveeded art a b r u p t decrease: at 1 K. Det~dls at b w t e m p e r a t u r e s are shown in Fig. 2. T h e resistivity shows a s m ~ t p e a k at 2.8 K, a sharp d r o p at 2.4 K, ~nd then a b r u p t l y decreases agmn from 1.3 K down to 0.47 K where the resistivity b e c o m e s zero. A n o m a l i e s at 2.8 a~Ld 2.4 K c o r r e s p o n d to the i n c o m m e n s u r a t e and commc~s u r a t e a n t i f e r r o m a g n e t i c t r a n s i t i o n s , respectively, r e p o r t e d by M o o d e n b a u g h ef el ht the neutrcm diffraction meatsurements [4]. T h e s u p e r c o n d u c t ing t r a n s i t i o n is r a t h e r b r o a d as t}te width betw,;en 10 % and 90 % of the resistive t r a n s i t i o n is e s t i m a t e d to be AT~ = 0.67 K. T h e m i d p o i n t of resistive t r a n s i t i o n is 0.93 K. No evidence of r e e n t r a n t b e h a v i o r was observed down to 0.1 K. To d e t e r m i n e the t e m p e r a t u r e dependenc~ of the u p p e r critical field, He2, the rnagnetoresist a n c e m e a s u r e m e n t s of Er~FesSis were done at several t e m p e r a t u r e s . T h e m a g n e t i c field is applied up to 30 kOe parallel to curreitt dir~ctic,n. T r a n s i t i o n s to the n o r m a l s t a t e were. observed u nder fields up to 3 kOe ~s shown in Fig.3. Th~ He2 defined as a rcddpoint of resistive t r a n s i t i o n is obtained as ~ function of t e m p e r a t u r e ms shown lit Fig.4. The initial slope of Ho(T) at T~, (dH,~/dT)T,, is o b t a i n e d to b e - 1 . 9 k O e / K . T h e W H H t h e o r y [6] for the calculation of H~2(T) provides a good fit to the e x p e r i m e n t a l d a t a as drawr~ by a dotted line in Fig.4. T h e z e r o - t e m p e r a t u r e critical
{~1 0
I
I
!
0.5
t
t
I ~___
]
TEMPERATURE(K) Figure 4 Lg~(T) curve of Er~F{~3Sis The ff~ is determined from a midpoint of the resistive t r a n s i t i o n l)otted line is obtained from the WHIt fitting wi~h A. . . . ~ [q.
field He2(0) is e s t i m a t e d to be 1.3 kOe. Since tl~<~ value is considered as orbitaJ, critical field, the G L coherence length ~c0 is e s t i m a t e d to be (u = 500 k. []~ s u m m a r y , a new m a g n e t i c s u p e r c o n d u c t o r gr2FegSis was found. T h e zero resistive transition t e m p e r a t u r e is c,t,tained to be T~(, = 0.47 K below the i n c o m m e n s u r a t e anti c o m m e n s u r a t e a n t l f e r r o m a g n e t i c t r a n s i t i o n at 2.8 and 2.4 K, respectively. Dora the H~2(T) curve, (dHo/dT)>: and He2(0 ) are e s t i m a t e d to be -1.q k O e / K ~nd 1.3 kOe, respectively. T h e coherence length is ~.st i m a t e d to be ~0 = 500 It.
References 1. O1. Bodak, B.Ya. Kotur, V I . Yarovets and E.1. Gradyshevskii, Soy. Phys. Crystallogr. 22 (1977) 217. 2 H.F. Braun, Phys. L e t t 75A (1980) 38(;. 3. C.B. Vining and R N . Shetton, Phys. R e v B28 (198a) 2rv_3. 4 A.K. Moodenbaugh, D.E. Cox, C.B. Vinmg anti C.U. Segre, Phys. Rev. B29 (1984) 271 5. J. A. Gotaas, J. W. Lynn, R N. Shelton, P Klavins and H.F. Braun, P h y s Rev. BS6 (1987) 7277. 6 N. R. Werthamer, E. Helfand and P . C . Hohenberg, Phys. Rev. Lett. 52 (1966) 295