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magnetic stannides
Mat. Res. Bull., Vol. 15, pp. 1635-1641, 1980. Printed in the USA. 0025-5408/80/111635-07502.00/0 Copyright (c) 1980 Pergamon Press Ltd.
C R Y S T A L CHEMISTRY, GROWTH AND R E E N T R A N T B E H A V I O R OF A D D I T I O N A L S U P E R C O N D U C T I N G / M A G N E T I C STANNIDES
G. P. Espinosa, A. S. Cooper, H. Barz and J. P. Remeika Bell Laboratories, Murray Hill, NJ 07974
(Received September 8, 1980; Commumcated by N. B. Hannay)
ABSTRACT Single crystals of c o m p o u n d s in the systems (M)-Os-Sn, (M)-Os-Pt-Sn, (M)-Pt-Sn; (M)-Ru-Sn, (M)-Ru-Pd-Sn and (M)-Pd-Sn, with M = Er, Y, La, Ca or Yb, have been grown from a tin solvent in vacuo. The c o m p o u n d E r O s x S n v has been found to be a r e e n t r a n t s u p e r c o n d u c t o r with T c = 1.25 K and T m = 0.45 K. Lattice parameters, superc o n d u c t i n g and m a g n e t i c t r a n s i t i o n temperatures, and chemical analyses are given.
Introduction R e c e n t l y a n e w family of s u p e r c o n d u c t i n g and/or m a g n e t i c single crystal t e r n a r y stannides was d e s c r i b e d (i). Because our interests are in c o e x i s t e n c e or p r o x i m i t y effects of m a g n e t i s m and s u p e r c o n d u c t i v i t y , the p r e s e n t w o r k is part of an o n g o i n g p r o g r a m of a search for new compounds w i t h those properties. In this paper we d e s c r i b e m o r e compounds that are i s o s t r u c t u r a l or s t r u c t u r a l l y r e l a t e d to those a l r e a d y reported (2-4). We are here c o n c e r n e d w i t h the systems (M)-Os-Sn, (M)-Os-Pt-Sn, (M)-PtSn; (M)-Ru-Sn, (M)-Ru-Pd-Sn, and (M)-Pd-Sn w h e r e M = Er, Y, La, Ca or Yb. C r y s t a l growth, c r y s t a l l o g r a p h i c , a n a l y t i c a l and s u p e r c o n d u c t i n g or m a g n e t i c t r a n s i t i o n data are presented. Experimental The r e q u i r e d q u a n t i t i e s of the starting elements, (minim u m p u r i t y 99.9% except for Sn w h i c h was 99.999%), were sealed into e v a c u a t e d fused silica tubes (ii m m O.D., 1 m m wall thickness, 8 cm long). The tubes w e r e held v e r t i c a l l y in a l u m i n u m oxide c r u c i b l e s and p l a c e d in a r e s i s t i v e l y heated furnace programmed for a soak time of 2 hours at 1050°C and a cooling rate of 3 to 10°C/hr. Growth e x p e r i m e n t s w e r e t e r m i n a t e d at approxim a t e l y 550°C when the tubes were r e m o v e d from the furnace and 1635
1636
G.P.
ESPINOSA, et al.
Vol. 15, No. 11
a l l o w e d to c o o l to r o o m t e m p e r a t u r e . The crystals were separated f r o m t h e s o l i d i f i e d m e l t by s o a k i n g in c o n c e n t r a t e d hydrochloric acid and were removed from the acid immediately upon separation f r o m t h e i n g o t to a v o i d a c i d a t t a c k . It s h o u l d be m e n t i o n e d h e r e t h a t t h e u s e o f t h i s t e c h n i q u e to p r o d u c e s i n g l e c r y s t a l s o f n e w c o m p o u n d s h a s w i t h i n it t h e i n h e r e n t d i s a d v a n t a g e of possible phase loss during acid extraction. If t h e d e s i r e d p h a s e is a t t a c k e d b y t h e e x t r a c t i n g a c i d at t h e s a m e r a t e as t h e s o l i d i f i e d s o l v e n t , it w i l l n o t be r e c o v e r e d ; t h e r e f o r e , o t h e r p r e p a r a t i v e techniques, s u c h as s o l i d - s o l i d r e a c t i o n , m u s t be e m p l o y e d to determine boundaries. Melt compositions a r e g i v e n in t h e t a b l e . E l e m e n t a l s u b s c r i p t s in c o l u m n I o f t h e t a b l e a r e e m p l o y e d o n l y to define the starting composition of the melt. The crystals were characterized with X-ray powder diffraction photographs t a k e n in a 1 1 4 . 6 m m D e b y e - S c h e r r e r camera with filtered CrK u radiation. L a t t i c e p a r a m e t e r s a r e g i v e n in t h e table along with superconducting transition temperatures (T c) g r e a t e r t h a n 1.1 K w h i c h w e r e m e a s u r e d i n d u c t i v e l y a t a f r e q u e n c y o f 13 c y c l e s . TABLE I Formulations, Phases, Transition Temperatures and Lattice Parameters Weight of Melt (gm)
Melt Composition (mole %) (M)
(M)
x
y
Major Phase (s) a
Trans. T c (K)
Lattice Parameter (~)
z
~Tc=1.25 e
ErOs Sn x z
3.08
6.16
--
90.76
6.0715
III
ErOs Pt Sn x y z ErPt Sn • y z" ErRu Sn x z ErRu Pd Sn x y z ErPd Sn y z YOs Sn
3.08
3.08
3.08
90.76
12.1577
III
not to i.i
3.84
--
3.66
92.50
2.2472
hex b
not to 1.1
3.84
3.66
--
92.50
2.1845
III*
not to 1.1
13.734
3.08
3.08
3.08
90.77
11.6242
III*
not to i.i
13.735
3.84
--
3.66
92.50
2.1881
?c
not to 1.1
6.67
3.34
--
90.00
5.9591
III
2.5-2.3
13.801
YOs Pt Sn x y z YOs Pt Sn x y z YOs Pt Sn x y z YPt Sn y z YRu Sn x z
6.67
1.67
1.67
90.00
5.9632
III
not to i.i
13.806
3.45
1.72
1.72
93.10
5.8149
III
not to i.i
13.807
2.30
2.30
2.30
93.10
8.8089
III
not to 1.1
13.809
6.67
--
3.34
89.99
5.9673
hex b
not to 1.1
3.34
6.68
--
89.99
5.8308
III*,V
1.3-1.2
13.772
YRUxPdySnz
3.34
3.34
3.34
89.99
5.8397
III*
not to I.i
13.777
YPd Sn y z LaOs Sn x z LaOs Pt Sn x y z
3.34
--
6.67
89.99
5.8486
no y i e l d f
6.74
2.25
--
91.01
9.0298
Os+? c
not to i.i
6.74
1.12
1.12
91.02
9.0339
I
2.4-?
x
lTm=0.45
13.760 13.769
z
9.799
Vol. 15, No. 11
STANNIDES
TABLE
I
LaPt Sn y z L a R u Sn x z L a R u Pd Sn x y z L a R u P d Sn x y z LaPd Sn y z CaOs Sn x z CaOs P t S n x y z
(Continued) Weight of M e l t (gin)
Melt Composition (mole %)
(M)
1637
Major P h a s e (s) a
Trans. Tc(K)
Lattice Parameter (~)
(M)
x
y
z
6.74
--
2.25
91.01
9.0380
cubic d
not to 1.1
6.74
2.25
--
91.01
8.8812
I
3.9-3.2
9.772
6.74
1.12
1.12
91.02
8.8857
I
4.6-4.0
9.776
6.74
0.57
1.68
91.01
8.8880
I
4.8-4.5
9.780
6.74
--
2.25
91.01
8.8902
?c
not to 1.1
6.45
6.45
--
87.09
6.1135
Os
6.46
3.23
3.23
87.07
6.1217
I*
1.9-1.5
15.63
9.761 9.776
9.76
C a P t Sn y z
6.45
--
6.45
87.09
6.1299
I*
n o t to i.i
C a R u Sn x z C a R u P d Sn x y z C a R u P d Sn x y z C a P d Sn y z YbOs Sn x z YbOs P t Sn x y z Y b O s Pt Sn x y z
6.16
3.08
--
90.76
5.5218
V
not to 1.1
9.353
6.73
1.13
1.13
91.02
7.3260
V
n o t to I.I
9.35
3.34
3.34
3.34
89.99
5.7583
V
not to i.i
9.35
6.45
--
6.45
87.09
5.8340
?c
not to. 1.1
3.33
6.66
--
90.01
6.2683
Os
3.33
3.33
3.33
90.1
6.2765
I
not to i.i
6.74
1.12
1.12
91.02
9.2043
I*
not to 1.1
3.33
--
6.66
90.01
6.2847
?c
not to i.i
3.18
3.18
--
93.65
11.3223
V
n o t to 1.1
9.35
6.16
3.08
--
90.76
5.9207
V
not to 1.1
9.35
6.73
1.12
1.12
91.02
7.9064
V
not to i.I
9.35
3.18
--
3.18
93.64
5.6692
no y i e l d f
Y b P t Sn y z YbRUxS~z Y b R u Sn x z Y b R u Pd Sn x y z Y b P d Sn y z aRecovered
after
acid extraction.
bHexagonal
(M)PtSn(8).
Cunidentified phase. d e f
Composition
unknown.
ac s u s c e p t i b i l i t y i.e.
after
measurements
transition).
acid e x t r a c t i o n .
Phase
I
- Primitive
Ph a s e
I*
- See text.
Ph a s e
III
- Face
Ph a s e
III*-
Ph a s e V
(Tm = m a g n e t i c
cubic.
centered
Slightly
cubic.
distorted
- I r 3 S n 7 structure,
phase body
III.
centered
cubic
(6).
9.78
9.750 9.755 9.744
1638
G.P.
ESPINOSA,
et al.
Vol. 15, No. II
Discussion In keeping with the phase designations employed in earlier publications (i-4), phase I will refer to a primitive cubic structure, space group Pm3m. C r y s t a l l o g r a p h i c and analytical d a t a have indicated an ideal phase I composition of (M) 6(Rh)sSn26 (4,5) where (M) is a rare earth larger than Gd or the elemen£s Ca, Sr or Th. The compounds designated phase I* have X-ray powder patterns similar to YbRh I 4Sn~ 6 which showed line doubling in the back reflection region anu'was called phase I in (i), and referred to as phase IV in (2,3). This effect has been shown (5), for the Yb compound, to be due to the presence of two cubic lattices of slightly varying size in one crystal. In this paper we refer to these compounds as a special case of phase I and report the lattice constants for the two cubic lattices. Phase III is face centered cubic, space group Fm3m. Several compounds have been designated as phase III* to indicate a very slight distortion from phase III. X-ray patterns of phase III* contain the fcc reflections of phase III plus one additional reflection at d = 2.71. This reflection is the most intense of those which differentiate phase III from phase II. Phase II now appears to be a tetra@onal superstructure of phase III with a o = 13.7 A and c o = 27.4 A (5). Lattice constants are reported in the table based on fcc indexing for phases III and III*. From previous work (i) phases II and III compositions have fallen in the range (M)(Rh)l.1_l.3Sn3.6_4. 0 depending on the element (M). Phase V possesses the Ir3Sn 7 structure (6). The present choice of (M) was based on the results of previous work (i). La and Y were chosen as large and small substituents, Yb and Ca for forming compounds w i t h the highest Tc'S in the system (M)-Rh-Sn and Er for exhibiting reentrant superconductivity for ErRhl.iSn3. 6. (M)-Os-Sn,
(M)-Os-Pt-Sn,
(M)-Pt-Sn
(M) = Er or Y. Phase III was found for both the (M)-Os-Sn and (M)-Os-Pt~Sn systems. Crystals of ErOs..Sn., proved to be reentrant superconductors with T c = 1.25 K and T m = 0.45 K (7). These transitions are remarkably close to those for ErRhl.iSn3. 6 (T c = 0.97 K and T m = 0.57 K), the only other reentrant superconductor found thus far in our investigation of the stannides. The YOsxSn Y compound showed an onset of superconductivity at % 2.5 K. Partial substitution of Pt for Os rendered the resultant phase III compounds n o n s u p e r c o n d u c t i n g to i.i K. For the Pt end member formulations a hexagonal phase of the reported composition (M)PtSn (8) was obtained, which was not superconducting to i.I K. ~ ) = La. Phase I was obtained from the system La-Os-Pt-Sn w i t h the onset of s u p e r c o n d u c t i v i t y at 2.4 K and extending to below i.I K. The system La-Os-Sn yielded only Os
Vol. 15, No. I I
STANNIDES
1639
upon acid e x t r a c t i o n and L a - P t - S n r e s u l t e d in a phase indexed as cubic, a o = 15.63 ~, w h i c h was not s u p e r c o n d u c t i n g above i.i K. M = Ca. F r o m the systems C a - O s - P t - S n and C a - P t - S n phase I* was obtained• In the former system a T c of 1.9-1.5 K was measured w h i l e the Pt end member, a n a l y z e d to give the c o m p o s i t i o n CaPt 1.4 Sn4 •3, was not s u p e r c o n d u c t i n g above I.i K. Only Os was r e c o v e r e d after acid e x t r a c t i o n of the C a - O s - S n s o l i d i f i e d melt. S o l i d i f i e d melts of systems such as La-Os-Sn and C a - O s - S n which do not survive acid e x t r a c t i o n will have to be tried by other reaction techniques. M = Yb. Phases I and I* c r y s t a l l i z e d from the mixed system, Yb-Os-Pt-Sn, d e p e n d i n g on the ratios of the starting elements (see table)• N e i t h e r c o m p o u n d was s u p e r c o n d u c t i n g to i.i K. It is i n t e r e s t i n g to note that the a v e r a g e of the lattice p a r a m e t e r s of the two cubic s t r u c t u r e s o b s e r v e d for phase I* is equal to the lattice p a r a m e t e r of phase I. The Y b - O s - S n solidified m e l t y i e l d e d only Os after acid extraction. An u n i d e n t i f i e d n o n s u p e r c o n d u c t i n g (to i.I K) phase was r e c o v e r e d from the Yb-PtSn system. It should be p o i n t e d out that the r e s u l t a n t crystals from the systems w h i c h contain Os, d e s c r i b e d above, are o f t e n contaminated w i t h Os. X-ray p o w d e r p h o t o g r a p h s indicate that this i m p u r i t y is only minor. An a t t e m p t was made to prepare Y b 6 O s s S n 2 6 and C a 6 0 s s S n 2 6 from the s t o i c h i o m e t r i c melt. The starting elements were pelletized and h e a t e d in an e v a c u a t e d fused silica tube for 15 min. at i1500C, then c o o l e d in air. While this t e c h n i q u e had p r o v e d s u c c e s s f u l for the p r e p a r a t i o n of La6Rh8Sn26, it was u n s u c c e s s f u l for the a f o r e m e n t i o n e d two formulations. (M)-Ru-Sn,
(M)-Ru-Pd-Sn,
(M)-Pd-Sn
M = Er or Y. Phase III* was o b t a i n e d from both the systems (M)-Ru-Sn and (M)-Ru-Pd-Sn. The results of chemical a n a l y s e s for M = Y gave the c o m p o s i t i o n s YRu I lSn3 1 and YRUl • 08 Pd 0. 0 4 Sn3 .2" The former c o m p o u n d e x h i b i t e d ' t h e onset of s u p e r o o n d u c t l v i t y at 1.3 K while the Pd s u b s t i t u t e d c o m p o u n d was not s u p e r c o n d u c t i n g to I.i K. The s u b s t i t u t i o n of Pd was accomp a n i e d by a small increase in lattice c o n s t a n t (see table). The c o r r e s p o n d i n g Er c o m p o u n d s were not s u p e r c o n d u c t i n g to I.i K. The end m e m b e r formulation, (M)-Pd-Sn, y i e l d e d an u n i d e n t i f i e d n o n s u p e r c o n d u c t i n g , (to i.i K), phase w h e n M = Er and for M = Y did not survive acid extraction. M = La. Crystals of phase I w e r e r e c o v e r e d for all f o r m u l a t i o n s e x c e p t in the L a - P d - S n s y s t e m w h i c h y i e l d e d an u n i d e n t i f i e d phase. W i t h i n c r e a s i n g Pd substitution, T c increases f r o m ~ 3.9 K for the Ru end member, a n a l y z e d as LaRUl.5Sn4. 5, to ~ 4.8 K for the m i x e d c o m p o u n d a n a l y z e d as
1640
G.P.
ESPINOSA, et al.
LaRUl 1 Pdn lSn4 3" The lattice p@rameter subst~tut[6n from 9.772 to 9.780 X.
Vol. 15, No. 11
also increased
with Pd
Because the crystal yield diminished greatly when increasing the Pd concentration of the melt, an attempt was m a d e to produce a compound with higher Pd substitution from the direct melt, i.e. no excess Sn. A near stoichiometric formulation was prepared and melted at i175°C for 15 min. in an evacuated fused silica tube which was then air cooled. The resultant product was not quite single phase but still ~howed a T c of ~ 5.6 K and a phase I lattice parameter of 9.776 A. Further e x p e r i m e n t a t i o n would be required to determine if the higher T c results from a compositional change or ordering of the structure because of a different thermal history. M = Ca or Yb. Crystals of phase V were o b t a i n e d for all formulations except for the Pd-Sn combinations. Ca-Pd-Sn yielded an unidentified phase and Yb-Pd-Sn did not survive acid extraction. o The phase V lattice parameters are all about equal to 9.35 A, the Ru3Sn 7 lattice parameter. This suggests that little or no (M) component entered the product where crystals or phase V resulted. Summary We have synthesized crystals of the new reentrant phase III superconductor, ErOsxSnv, which, in addition to ErRhl.iSn3.6, is the second reentrant superconductor found in our ongolng investigation of the stannides. The compound, CaPt I 4Sn4 ~ (phase I*), represents the first Pt end member isostructura['to other stannides which we have prepared in our recent work (1,2). The partial substitution of Pd for Ru in the (M)-Ru-Sn system compounds has been shown to either increase or decrease depending on the M element and resultant structure.
Tc
In general the crystal size and yield from the systems studied here were smaller than in our previous work (1,2). Further investigation of component solubility and crystal growth conditions is in progress to obtain larger crystals of the reentrant ErOsxSny compound. References i.
J. P. Remeika, G. P. Espinosa, A. S. Cooper, H. Barz, J. M. Rowell, D. B. McWhan, J. M. Vandenberg, D. E. Moncton, Z. Fisk, L. D.- Woolf, H. C. Hamaker, M. B. Maple, G. Shirane, and W. Thomlinson, Solid State Comm. 34, 923 (1980).
2.
G. P. Espinosa,
Mat.
Res.
Bull.
15,
791
(1980).
Vol. 15, No. 11
STANNIDES
3.
A. S. Cooper, Mat.
4.
J. M. Vandenberg,
5.
J. L. Hodeau, J. Chenavas, M. Marezio, Solid State Comm. (to be published).
6.
O. Nial,
7.
Z. Fisk, U n i v e r s i t y of California, (.private communication).
8.
A. E. Dwight, W. C. Harper and C. W. Kimball, Met. 30, 1 (1973).
Svensk.
Res. Bull. 15,
1641
Mat.
799
Res. Bull. 15,
Kem. Tidskr.
59, 433
(1980). 835
(1980).
and J. P. Remeika, (1947).
San Diego,
La Jolla,
CA
J. Less Common
C R Y S T A L CHEMISTRY, GROWTH AND R E E N T R A N T B E H A V I O R OF A D D I T I O N A L S U P E R C O N D U C T I N G / M A G N E T I C STANNIDES
G. P. Espinosa, A. S. Cooper, H. Barz and J. P. Remeika Bell Laboratories, Murray Hill, NJ 07974
(Received September 8, 1980; Commumcated by N. B. Hannay)
ABSTRACT Single crystals of c o m p o u n d s in the systems (M)-Os-Sn, (M)-Os-Pt-Sn, (M)-Pt-Sn; (M)-Ru-Sn, (M)-Ru-Pd-Sn and (M)-Pd-Sn, with M = Er, Y, La, Ca or Yb, have been grown from a tin solvent in vacuo. The c o m p o u n d E r O s x S n v has been found to be a r e e n t r a n t s u p e r c o n d u c t o r with T c = 1.25 K and T m = 0.45 K. Lattice parameters, superc o n d u c t i n g and m a g n e t i c t r a n s i t i o n temperatures, and chemical analyses are given.
Introduction R e c e n t l y a n e w family of s u p e r c o n d u c t i n g and/or m a g n e t i c single crystal t e r n a r y stannides was d e s c r i b e d (i). Because our interests are in c o e x i s t e n c e or p r o x i m i t y effects of m a g n e t i s m and s u p e r c o n d u c t i v i t y , the p r e s e n t w o r k is part of an o n g o i n g p r o g r a m of a search for new compounds w i t h those properties. In this paper we d e s c r i b e m o r e compounds that are i s o s t r u c t u r a l or s t r u c t u r a l l y r e l a t e d to those a l r e a d y reported (2-4). We are here c o n c e r n e d w i t h the systems (M)-Os-Sn, (M)-Os-Pt-Sn, (M)-PtSn; (M)-Ru-Sn, (M)-Ru-Pd-Sn, and (M)-Pd-Sn w h e r e M = Er, Y, La, Ca or Yb. C r y s t a l growth, c r y s t a l l o g r a p h i c , a n a l y t i c a l and s u p e r c o n d u c t i n g or m a g n e t i c t r a n s i t i o n data are presented. Experimental The r e q u i r e d q u a n t i t i e s of the starting elements, (minim u m p u r i t y 99.9% except for Sn w h i c h was 99.999%), were sealed into e v a c u a t e d fused silica tubes (ii m m O.D., 1 m m wall thickness, 8 cm long). The tubes w e r e held v e r t i c a l l y in a l u m i n u m oxide c r u c i b l e s and p l a c e d in a r e s i s t i v e l y heated furnace programmed for a soak time of 2 hours at 1050°C and a cooling rate of 3 to 10°C/hr. Growth e x p e r i m e n t s w e r e t e r m i n a t e d at approxim a t e l y 550°C when the tubes were r e m o v e d from the furnace and 1635
1636
G.P.
ESPINOSA, et al.
Vol. 15, No. 11
a l l o w e d to c o o l to r o o m t e m p e r a t u r e . The crystals were separated f r o m t h e s o l i d i f i e d m e l t by s o a k i n g in c o n c e n t r a t e d hydrochloric acid and were removed from the acid immediately upon separation f r o m t h e i n g o t to a v o i d a c i d a t t a c k . It s h o u l d be m e n t i o n e d h e r e t h a t t h e u s e o f t h i s t e c h n i q u e to p r o d u c e s i n g l e c r y s t a l s o f n e w c o m p o u n d s h a s w i t h i n it t h e i n h e r e n t d i s a d v a n t a g e of possible phase loss during acid extraction. If t h e d e s i r e d p h a s e is a t t a c k e d b y t h e e x t r a c t i n g a c i d at t h e s a m e r a t e as t h e s o l i d i f i e d s o l v e n t , it w i l l n o t be r e c o v e r e d ; t h e r e f o r e , o t h e r p r e p a r a t i v e techniques, s u c h as s o l i d - s o l i d r e a c t i o n , m u s t be e m p l o y e d to determine boundaries. Melt compositions a r e g i v e n in t h e t a b l e . E l e m e n t a l s u b s c r i p t s in c o l u m n I o f t h e t a b l e a r e e m p l o y e d o n l y to define the starting composition of the melt. The crystals were characterized with X-ray powder diffraction photographs t a k e n in a 1 1 4 . 6 m m D e b y e - S c h e r r e r camera with filtered CrK u radiation. L a t t i c e p a r a m e t e r s a r e g i v e n in t h e table along with superconducting transition temperatures (T c) g r e a t e r t h a n 1.1 K w h i c h w e r e m e a s u r e d i n d u c t i v e l y a t a f r e q u e n c y o f 13 c y c l e s . TABLE I Formulations, Phases, Transition Temperatures and Lattice Parameters Weight of Melt (gm)
Melt Composition (mole %) (M)
(M)
x
y
Major Phase (s) a
Trans. T c (K)
Lattice Parameter (~)
z
~Tc=1.25 e
ErOs Sn x z
3.08
6.16
--
90.76
6.0715
III
ErOs Pt Sn x y z ErPt Sn • y z" ErRu Sn x z ErRu Pd Sn x y z ErPd Sn y z YOs Sn
3.08
3.08
3.08
90.76
12.1577
III
not to i.i
3.84
--
3.66
92.50
2.2472
hex b
not to 1.1
3.84
3.66
--
92.50
2.1845
III*
not to 1.1
13.734
3.08
3.08
3.08
90.77
11.6242
III*
not to i.i
13.735
3.84
--
3.66
92.50
2.1881
?c
not to 1.1
6.67
3.34
--
90.00
5.9591
III
2.5-2.3
13.801
YOs Pt Sn x y z YOs Pt Sn x y z YOs Pt Sn x y z YPt Sn y z YRu Sn x z
6.67
1.67
1.67
90.00
5.9632
III
not to i.i
13.806
3.45
1.72
1.72
93.10
5.8149
III
not to i.i
13.807
2.30
2.30
2.30
93.10
8.8089
III
not to 1.1
13.809
6.67
--
3.34
89.99
5.9673
hex b
not to 1.1
3.34
6.68
--
89.99
5.8308
III*,V
1.3-1.2
13.772
YRUxPdySnz
3.34
3.34
3.34
89.99
5.8397
III*
not to I.i
13.777
YPd Sn y z LaOs Sn x z LaOs Pt Sn x y z
3.34
--
6.67
89.99
5.8486
no y i e l d f
6.74
2.25
--
91.01
9.0298
Os+? c
not to i.i
6.74
1.12
1.12
91.02
9.0339
I
2.4-?
x
lTm=0.45
13.760 13.769
z
9.799
Vol. 15, No. 11
STANNIDES
TABLE
I
LaPt Sn y z L a R u Sn x z L a R u Pd Sn x y z L a R u P d Sn x y z LaPd Sn y z CaOs Sn x z CaOs P t S n x y z
(Continued) Weight of M e l t (gin)
Melt Composition (mole %)
(M)
1637
Major P h a s e (s) a
Trans. Tc(K)
Lattice Parameter (~)
(M)
x
y
z
6.74
--
2.25
91.01
9.0380
cubic d
not to 1.1
6.74
2.25
--
91.01
8.8812
I
3.9-3.2
9.772
6.74
1.12
1.12
91.02
8.8857
I
4.6-4.0
9.776
6.74
0.57
1.68
91.01
8.8880
I
4.8-4.5
9.780
6.74
--
2.25
91.01
8.8902
?c
not to 1.1
6.45
6.45
--
87.09
6.1135
Os
6.46
3.23
3.23
87.07
6.1217
I*
1.9-1.5
15.63
9.761 9.776
9.76
C a P t Sn y z
6.45
--
6.45
87.09
6.1299
I*
n o t to i.i
C a R u Sn x z C a R u P d Sn x y z C a R u P d Sn x y z C a P d Sn y z YbOs Sn x z YbOs P t Sn x y z Y b O s Pt Sn x y z
6.16
3.08
--
90.76
5.5218
V
not to 1.1
9.353
6.73
1.13
1.13
91.02
7.3260
V
n o t to I.I
9.35
3.34
3.34
3.34
89.99
5.7583
V
not to i.i
9.35
6.45
--
6.45
87.09
5.8340
?c
not to. 1.1
3.33
6.66
--
90.01
6.2683
Os
3.33
3.33
3.33
90.1
6.2765
I
not to i.i
6.74
1.12
1.12
91.02
9.2043
I*
not to 1.1
3.33
--
6.66
90.01
6.2847
?c
not to i.i
3.18
3.18
--
93.65
11.3223
V
n o t to 1.1
9.35
6.16
3.08
--
90.76
5.9207
V
not to 1.1
9.35
6.73
1.12
1.12
91.02
7.9064
V
not to i.I
9.35
3.18
--
3.18
93.64
5.6692
no y i e l d f
Y b P t Sn y z YbRUxS~z Y b R u Sn x z Y b R u Pd Sn x y z Y b P d Sn y z aRecovered
after
acid extraction.
bHexagonal
(M)PtSn(8).
Cunidentified phase. d e f
Composition
unknown.
ac s u s c e p t i b i l i t y i.e.
after
measurements
transition).
acid e x t r a c t i o n .
Phase
I
- Primitive
Ph a s e
I*
- See text.
Ph a s e
III
- Face
Ph a s e
III*-
Ph a s e V
(Tm = m a g n e t i c
cubic.
centered
Slightly
cubic.
distorted
- I r 3 S n 7 structure,
phase body
III.
centered
cubic
(6).
9.78
9.750 9.755 9.744
1638
G.P.
ESPINOSA,
et al.
Vol. 15, No. II
Discussion In keeping with the phase designations employed in earlier publications (i-4), phase I will refer to a primitive cubic structure, space group Pm3m. C r y s t a l l o g r a p h i c and analytical d a t a have indicated an ideal phase I composition of (M) 6(Rh)sSn26 (4,5) where (M) is a rare earth larger than Gd or the elemen£s Ca, Sr or Th. The compounds designated phase I* have X-ray powder patterns similar to YbRh I 4Sn~ 6 which showed line doubling in the back reflection region anu'was called phase I in (i), and referred to as phase IV in (2,3). This effect has been shown (5), for the Yb compound, to be due to the presence of two cubic lattices of slightly varying size in one crystal. In this paper we refer to these compounds as a special case of phase I and report the lattice constants for the two cubic lattices. Phase III is face centered cubic, space group Fm3m. Several compounds have been designated as phase III* to indicate a very slight distortion from phase III. X-ray patterns of phase III* contain the fcc reflections of phase III plus one additional reflection at d = 2.71. This reflection is the most intense of those which differentiate phase III from phase II. Phase II now appears to be a tetra@onal superstructure of phase III with a o = 13.7 A and c o = 27.4 A (5). Lattice constants are reported in the table based on fcc indexing for phases III and III*. From previous work (i) phases II and III compositions have fallen in the range (M)(Rh)l.1_l.3Sn3.6_4. 0 depending on the element (M). Phase V possesses the Ir3Sn 7 structure (6). The present choice of (M) was based on the results of previous work (i). La and Y were chosen as large and small substituents, Yb and Ca for forming compounds w i t h the highest Tc'S in the system (M)-Rh-Sn and Er for exhibiting reentrant superconductivity for ErRhl.iSn3. 6. (M)-Os-Sn,
(M)-Os-Pt-Sn,
(M)-Pt-Sn
(M) = Er or Y. Phase III was found for both the (M)-Os-Sn and (M)-Os-Pt~Sn systems. Crystals of ErOs..Sn., proved to be reentrant superconductors with T c = 1.25 K and T m = 0.45 K (7). These transitions are remarkably close to those for ErRhl.iSn3. 6 (T c = 0.97 K and T m = 0.57 K), the only other reentrant superconductor found thus far in our investigation of the stannides. The YOsxSn Y compound showed an onset of superconductivity at % 2.5 K. Partial substitution of Pt for Os rendered the resultant phase III compounds n o n s u p e r c o n d u c t i n g to i.i K. For the Pt end member formulations a hexagonal phase of the reported composition (M)PtSn (8) was obtained, which was not superconducting to i.I K. ~ ) = La. Phase I was obtained from the system La-Os-Pt-Sn w i t h the onset of s u p e r c o n d u c t i v i t y at 2.4 K and extending to below i.I K. The system La-Os-Sn yielded only Os
Vol. 15, No. I I
STANNIDES
1639
upon acid e x t r a c t i o n and L a - P t - S n r e s u l t e d in a phase indexed as cubic, a o = 15.63 ~, w h i c h was not s u p e r c o n d u c t i n g above i.i K. M = Ca. F r o m the systems C a - O s - P t - S n and C a - P t - S n phase I* was obtained• In the former system a T c of 1.9-1.5 K was measured w h i l e the Pt end member, a n a l y z e d to give the c o m p o s i t i o n CaPt 1.4 Sn4 •3, was not s u p e r c o n d u c t i n g above I.i K. Only Os was r e c o v e r e d after acid e x t r a c t i o n of the C a - O s - S n s o l i d i f i e d melt. S o l i d i f i e d melts of systems such as La-Os-Sn and C a - O s - S n which do not survive acid e x t r a c t i o n will have to be tried by other reaction techniques. M = Yb. Phases I and I* c r y s t a l l i z e d from the mixed system, Yb-Os-Pt-Sn, d e p e n d i n g on the ratios of the starting elements (see table)• N e i t h e r c o m p o u n d was s u p e r c o n d u c t i n g to i.i K. It is i n t e r e s t i n g to note that the a v e r a g e of the lattice p a r a m e t e r s of the two cubic s t r u c t u r e s o b s e r v e d for phase I* is equal to the lattice p a r a m e t e r of phase I. The Y b - O s - S n solidified m e l t y i e l d e d only Os after acid extraction. An u n i d e n t i f i e d n o n s u p e r c o n d u c t i n g (to i.I K) phase was r e c o v e r e d from the Yb-PtSn system. It should be p o i n t e d out that the r e s u l t a n t crystals from the systems w h i c h contain Os, d e s c r i b e d above, are o f t e n contaminated w i t h Os. X-ray p o w d e r p h o t o g r a p h s indicate that this i m p u r i t y is only minor. An a t t e m p t was made to prepare Y b 6 O s s S n 2 6 and C a 6 0 s s S n 2 6 from the s t o i c h i o m e t r i c melt. The starting elements were pelletized and h e a t e d in an e v a c u a t e d fused silica tube for 15 min. at i1500C, then c o o l e d in air. While this t e c h n i q u e had p r o v e d s u c c e s s f u l for the p r e p a r a t i o n of La6Rh8Sn26, it was u n s u c c e s s f u l for the a f o r e m e n t i o n e d two formulations. (M)-Ru-Sn,
(M)-Ru-Pd-Sn,
(M)-Pd-Sn
M = Er or Y. Phase III* was o b t a i n e d from both the systems (M)-Ru-Sn and (M)-Ru-Pd-Sn. The results of chemical a n a l y s e s for M = Y gave the c o m p o s i t i o n s YRu I lSn3 1 and YRUl • 08 Pd 0. 0 4 Sn3 .2" The former c o m p o u n d e x h i b i t e d ' t h e onset of s u p e r o o n d u c t l v i t y at 1.3 K while the Pd s u b s t i t u t e d c o m p o u n d was not s u p e r c o n d u c t i n g to I.i K. The s u b s t i t u t i o n of Pd was accomp a n i e d by a small increase in lattice c o n s t a n t (see table). The c o r r e s p o n d i n g Er c o m p o u n d s were not s u p e r c o n d u c t i n g to I.i K. The end m e m b e r formulation, (M)-Pd-Sn, y i e l d e d an u n i d e n t i f i e d n o n s u p e r c o n d u c t i n g , (to i.i K), phase w h e n M = Er and for M = Y did not survive acid extraction. M = La. Crystals of phase I w e r e r e c o v e r e d for all f o r m u l a t i o n s e x c e p t in the L a - P d - S n s y s t e m w h i c h y i e l d e d an u n i d e n t i f i e d phase. W i t h i n c r e a s i n g Pd substitution, T c increases f r o m ~ 3.9 K for the Ru end member, a n a l y z e d as LaRUl.5Sn4. 5, to ~ 4.8 K for the m i x e d c o m p o u n d a n a l y z e d as
1640
G.P.
ESPINOSA, et al.
LaRUl 1 Pdn lSn4 3" The lattice p@rameter subst~tut[6n from 9.772 to 9.780 X.
Vol. 15, No. 11
also increased
with Pd
Because the crystal yield diminished greatly when increasing the Pd concentration of the melt, an attempt was m a d e to produce a compound with higher Pd substitution from the direct melt, i.e. no excess Sn. A near stoichiometric formulation was prepared and melted at i175°C for 15 min. in an evacuated fused silica tube which was then air cooled. The resultant product was not quite single phase but still ~howed a T c of ~ 5.6 K and a phase I lattice parameter of 9.776 A. Further e x p e r i m e n t a t i o n would be required to determine if the higher T c results from a compositional change or ordering of the structure because of a different thermal history. M = Ca or Yb. Crystals of phase V were o b t a i n e d for all formulations except for the Pd-Sn combinations. Ca-Pd-Sn yielded an unidentified phase and Yb-Pd-Sn did not survive acid extraction. o The phase V lattice parameters are all about equal to 9.35 A, the Ru3Sn 7 lattice parameter. This suggests that little or no (M) component entered the product where crystals or phase V resulted. Summary We have synthesized crystals of the new reentrant phase III superconductor, ErOsxSnv, which, in addition to ErRhl.iSn3.6, is the second reentrant superconductor found in our ongolng investigation of the stannides. The compound, CaPt I 4Sn4 ~ (phase I*), represents the first Pt end member isostructura['to other stannides which we have prepared in our recent work (1,2). The partial substitution of Pd for Ru in the (M)-Ru-Sn system compounds has been shown to either increase or decrease depending on the M element and resultant structure.
Tc
In general the crystal size and yield from the systems studied here were smaller than in our previous work (1,2). Further investigation of component solubility and crystal growth conditions is in progress to obtain larger crystals of the reentrant ErOsxSny compound. References i.
J. P. Remeika, G. P. Espinosa, A. S. Cooper, H. Barz, J. M. Rowell, D. B. McWhan, J. M. Vandenberg, D. E. Moncton, Z. Fisk, L. D.- Woolf, H. C. Hamaker, M. B. Maple, G. Shirane, and W. Thomlinson, Solid State Comm. 34, 923 (1980).
2.
G. P. Espinosa,
Mat.
Res.
Bull.
15,
791
(1980).
Vol. 15, No. 11
STANNIDES
3.
A. S. Cooper, Mat.
4.
J. M. Vandenberg,
5.
J. L. Hodeau, J. Chenavas, M. Marezio, Solid State Comm. (to be published).
6.
O. Nial,
7.
Z. Fisk, U n i v e r s i t y of California, (.private communication).
8.
A. E. Dwight, W. C. Harper and C. W. Kimball, Met. 30, 1 (1973).
Svensk.
Res. Bull. 15,
1641
Mat.
799
Res. Bull. 15,
Kem. Tidskr.
59, 433
(1980). 835
(1980).
and J. P. Remeika, (1947).
San Diego,
La Jolla,
CA
J. Less Common