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Change of sign of the Hall coefficient in liquid alloys
Volume 34A, number 6
PHYSICS LETTERS
It is worth noticing that the t h e r m a l conductivity m i n i m u m in FeC12 is o b s e r v e d to be s l i g h t ly shifted to lower t e m p e r a t u r e c o m p a r a t i v e l y to the Ndel point. Thus, the q u e s t i o n a r i s e s whether c r i t i c a l fluctuation is solely r e s p o n s i b l e of the t h e r m a l r e s i s t i v i t y peak or whether an additional r e s o n a n t s c a t t e r i n g is involved. Better u n d e r standing of these r e s u l t s will be achieved by i n v e s t i g a t i n g the t h e r m a l conductivity behavior in an applied magnetic field. M o r e o v e r , the c o n t r i bution of the u s u a l phonon s c a t t e r i n g m e c h a n i s m s at low t e m p e r a t u r e (boundary effects and m a s s difference s c a t t e r i n g ) r e q u i r e s the knowledge of e l a s t i c p a r a m e t e r s in these m a t e r i a l s .
5April1971
P a p o u l a r , and M. N a s s e r for d i s c u s s i o n s .
References [1] K.Kawasaki, Progr. Theor. Phys. (Japan) 29 (1963) 801. [2] H. Stern, J. Phys. Chem. Sol. 26 (1965) 153. [3] M. Papoular, J. Phys. (France) 28 (1967) C1-140. [4] G. A. Slack, Proc. Int. Conf. Semic. Prague, 1960 (Academic Press, New York, 1961); Phys. Rev. 122 (1961) 1451; Phys. Rev. 126 (1962) 427. [5] O. Bethoux, P. Thomas and J. Weil, C.R. Acad. Sc. Paris 253 (1961) 2043; 8th Int. Conf. Low Temperature Physics (1962). [6] H. J. Albany and G. Laurance, Solid State Comm. 7 (1969) 63; G. Laurence, These 3~me Cycle, Paris (1969).
The author wishes to thank Drs. Albany and * * * * *
CHANGE
OF
SIGN OF
THE
HALL
COEFFICIENT
IN L I Q U I D
ALLOYS
G. BUSCH, H. -J. G U N T H E R O D T and H. U. K U N Z I Laboratorium flar Festki~rperphysik ETH, Ziirich, Switzerland Received 12 March 1971
We have measured the Hall coefficients of several liquid alloys of normal metals with transition metals which show a positive Hall coefficient in the liquid state. We have found that the Hall coefficients are also positive for the transition metal rich alloys, decrease with increasing concentration of the normal metals, pass through zero and finally approach the negative Hall coefficients of the liquid normal metals.
A f t e r the f i r s t m e a s u r e m e n t s of p o s i t i v e Hall coefficients in pure liquid metals (La, Ce, Pr, Nd, U) [1] we have i n v e s t i g a t e d the m a n n e r in which the sign of the Hall coefficient changes when such m e t a l s a r e alloyed with liquid n o r m a l m e t a l s . The Hall coefficients of the liquid n o r m a l m e t a l s a g r e e with t h e i r r e s p e c t i v e f r e e e l e c t r o n v a l u e s i.e. the sign of the Hall coefficient is negative [2]. A s an example of our m e a s u r e m e n t s we d i s c u s s the Hall coefficients of liquid C u - C e and G e . F e . S i m i l a r b e h a v i o r h a s been o b s e r v e d for liquid C u - P r , C u - L a , G e - M n and A u - F e . Fig.1 shows the Hall coefficients of liquid C u - C e and G e - F e , r e s p e c t i v e l y . The Hall coeffic i e n t is negative for p u r e liquid Cu, p a s s e s through zero at 20 at. % Ce and is positive for p u r e liquid Ce. The Hall coefficient v a r i e s l i n e a r l y with Ce c o n c e n t r a t i o n up to 40at. % Ce, above which it r e m a i n s c o n s t a n t at the value for p u r e liquid Ce. F o r F e - G e alloys the Hall coefficient v a r i e s continuously f r o m the negative
,j ,o-.~' .6
.3 o -3
-6
/ Cu
i I0
j
/ I
!
J
] ZO
30
40 ~ %Ice
~
Ge
I0
20
30
40at % Fe
Fig.l.Hall coefficientof liquidCu-Ce and Fe-Ge value of liquid Ge to the large positive values of liquid Fe-rich alloys. The Hall coefficient changes sign at 27 at. % Fe and increases to very 309
Volume 34A. number 6
PHYSICS LETTERS
lacking. F r o m the e x p e r i m e n t a l facts it is suggested that the explanation must also be v a l i d for the solid state, since t h e r e is no change of sign of the Hall coefficient, and only a s m a l l change in the value, at the m e l t i n g point. P o s i t i v e Hall coefficients may be due to d e f e c t e l e c t r o n s or, as is being p r e s e n t l y investigated, due to the effects of s p i n - o r b i t coupling [3]. M e a s u r e m e n t s of the Hall coefficients of liquid C e - F e and C e - L a alloys, for which the Hall •coefficients of both components a r e positive, a r e in p r o g r e s s . We a r e also i n v e s t i g a t i n g the sign of t h e r m o p o w e r of those liquid m e t a l s and alloys which show a positive Hall coefficient.
,t
V~cm 150 - -
J
5 April 1971
O--
120
90
60
30
J
I0
20
30
4 0 O! % Ce
Ge
' I0
20
30
4 0 ot % Fe
Fig.2. Electrical resistivity of liquid Cu-Ce and Fe-Ge l a r g e positive v a l u e s for F e - r i c h alloys e.g. + 3 0 × 1 0 -11 m3,/A • s at 8 0 a t . % F e . We a r e s t i l l investigating the Hall coefficient of p u r e liquid Fe which s e e m s to be one of the l a r g e s t for liquid m e t a l s . Fig. 2 shows the e l e c t r i c a l r e s i s t i v i t i e s of liquid C u - C e and G e - F e alloys. The r e s i s t i v i t i e s of both Cu and Ge i n c r e a s e s u b s t a n t i a l l y upon alloying with Ce or Fe r e s p e c t i v e l y . The detailed b e h a v i o r of the e l e c t r i c a l r e s i s t i v i t y is s i m i l a r to that p r e v i o u s l y o b s e r v e d for liquid Co-Ge, Co-Sn, Ni-Ge and Ni-Sn, all of which, however, have negative Hall coefficients over the e n t i r e c o n c e n t r a t i o n r a n g e so far investigated. A t h e o r e t i c a l explanation of positive Hall coeffic i e n t s in p u r e liquid t r a n s i t i o n m e t a l s is s t i l l
310
We would like to thank Prof. W. B a l t e n s p e r g e r , Dr. T. M. Rice and Miss A. ten Bosch for d i s c u s sion and Prof. J. Bass for reading the m a n u s c r i p t . We a r e indebted to the "Schweizerische Nationalfonds zur Ft}rderung der w i s s e n s c h a f t lichen F o r s c h u n g " and to the R e s e a r c h i n s t i t u t e of A l u s u i s s e , for f i n a n c i a l support.
References [1] G. Busch, H.-J. Gilntherodt, H.U. KIlnzi and L. Schlapbach, Phys. Letters 31A (1970)191, 32A (1970) 376; G. Busch, H. -J. Gtintherodt, H. U. KUnzi, H.A. Meier and L. Schlapbsch, Mat. Res. Bull 5 (1970) 567. [2] G. Busch and H. -J. Gt/ntherodt, Phys. kondens. Materie 6 (1967) 325. [3] W. Bsltensperger and A. ten Bosch, private communication (1970).
PHYSICS LETTERS
It is worth noticing that the t h e r m a l conductivity m i n i m u m in FeC12 is o b s e r v e d to be s l i g h t ly shifted to lower t e m p e r a t u r e c o m p a r a t i v e l y to the Ndel point. Thus, the q u e s t i o n a r i s e s whether c r i t i c a l fluctuation is solely r e s p o n s i b l e of the t h e r m a l r e s i s t i v i t y peak or whether an additional r e s o n a n t s c a t t e r i n g is involved. Better u n d e r standing of these r e s u l t s will be achieved by i n v e s t i g a t i n g the t h e r m a l conductivity behavior in an applied magnetic field. M o r e o v e r , the c o n t r i bution of the u s u a l phonon s c a t t e r i n g m e c h a n i s m s at low t e m p e r a t u r e (boundary effects and m a s s difference s c a t t e r i n g ) r e q u i r e s the knowledge of e l a s t i c p a r a m e t e r s in these m a t e r i a l s .
5April1971
P a p o u l a r , and M. N a s s e r for d i s c u s s i o n s .
References [1] K.Kawasaki, Progr. Theor. Phys. (Japan) 29 (1963) 801. [2] H. Stern, J. Phys. Chem. Sol. 26 (1965) 153. [3] M. Papoular, J. Phys. (France) 28 (1967) C1-140. [4] G. A. Slack, Proc. Int. Conf. Semic. Prague, 1960 (Academic Press, New York, 1961); Phys. Rev. 122 (1961) 1451; Phys. Rev. 126 (1962) 427. [5] O. Bethoux, P. Thomas and J. Weil, C.R. Acad. Sc. Paris 253 (1961) 2043; 8th Int. Conf. Low Temperature Physics (1962). [6] H. J. Albany and G. Laurance, Solid State Comm. 7 (1969) 63; G. Laurence, These 3~me Cycle, Paris (1969).
The author wishes to thank Drs. Albany and * * * * *
CHANGE
OF
SIGN OF
THE
HALL
COEFFICIENT
IN L I Q U I D
ALLOYS
G. BUSCH, H. -J. G U N T H E R O D T and H. U. K U N Z I Laboratorium flar Festki~rperphysik ETH, Ziirich, Switzerland Received 12 March 1971
We have measured the Hall coefficients of several liquid alloys of normal metals with transition metals which show a positive Hall coefficient in the liquid state. We have found that the Hall coefficients are also positive for the transition metal rich alloys, decrease with increasing concentration of the normal metals, pass through zero and finally approach the negative Hall coefficients of the liquid normal metals.
A f t e r the f i r s t m e a s u r e m e n t s of p o s i t i v e Hall coefficients in pure liquid metals (La, Ce, Pr, Nd, U) [1] we have i n v e s t i g a t e d the m a n n e r in which the sign of the Hall coefficient changes when such m e t a l s a r e alloyed with liquid n o r m a l m e t a l s . The Hall coefficients of the liquid n o r m a l m e t a l s a g r e e with t h e i r r e s p e c t i v e f r e e e l e c t r o n v a l u e s i.e. the sign of the Hall coefficient is negative [2]. A s an example of our m e a s u r e m e n t s we d i s c u s s the Hall coefficients of liquid C u - C e and G e . F e . S i m i l a r b e h a v i o r h a s been o b s e r v e d for liquid C u - P r , C u - L a , G e - M n and A u - F e . Fig.1 shows the Hall coefficients of liquid C u - C e and G e - F e , r e s p e c t i v e l y . The Hall coeffic i e n t is negative for p u r e liquid Cu, p a s s e s through zero at 20 at. % Ce and is positive for p u r e liquid Ce. The Hall coefficient v a r i e s l i n e a r l y with Ce c o n c e n t r a t i o n up to 40at. % Ce, above which it r e m a i n s c o n s t a n t at the value for p u r e liquid Ce. F o r F e - G e alloys the Hall coefficient v a r i e s continuously f r o m the negative
,j ,o-.~' .6
.3 o -3
-6
/ Cu
i I0
j
/ I
!
J
] ZO
30
40 ~ %Ice
~
Ge
I0
20
30
40at % Fe
Fig.l.Hall coefficientof liquidCu-Ce and Fe-Ge value of liquid Ge to the large positive values of liquid Fe-rich alloys. The Hall coefficient changes sign at 27 at. % Fe and increases to very 309
Volume 34A. number 6
PHYSICS LETTERS
lacking. F r o m the e x p e r i m e n t a l facts it is suggested that the explanation must also be v a l i d for the solid state, since t h e r e is no change of sign of the Hall coefficient, and only a s m a l l change in the value, at the m e l t i n g point. P o s i t i v e Hall coefficients may be due to d e f e c t e l e c t r o n s or, as is being p r e s e n t l y investigated, due to the effects of s p i n - o r b i t coupling [3]. M e a s u r e m e n t s of the Hall coefficients of liquid C e - F e and C e - L a alloys, for which the Hall •coefficients of both components a r e positive, a r e in p r o g r e s s . We a r e also i n v e s t i g a t i n g the sign of t h e r m o p o w e r of those liquid m e t a l s and alloys which show a positive Hall coefficient.
,t
V~cm 150 - -
J
5 April 1971
O--
120
90
60
30
J
I0
20
30
4 0 O! % Ce
Ge
' I0
20
30
4 0 ot % Fe
Fig.2. Electrical resistivity of liquid Cu-Ce and Fe-Ge l a r g e positive v a l u e s for F e - r i c h alloys e.g. + 3 0 × 1 0 -11 m3,/A • s at 8 0 a t . % F e . We a r e s t i l l investigating the Hall coefficient of p u r e liquid Fe which s e e m s to be one of the l a r g e s t for liquid m e t a l s . Fig. 2 shows the e l e c t r i c a l r e s i s t i v i t i e s of liquid C u - C e and G e - F e alloys. The r e s i s t i v i t i e s of both Cu and Ge i n c r e a s e s u b s t a n t i a l l y upon alloying with Ce or Fe r e s p e c t i v e l y . The detailed b e h a v i o r of the e l e c t r i c a l r e s i s t i v i t y is s i m i l a r to that p r e v i o u s l y o b s e r v e d for liquid Co-Ge, Co-Sn, Ni-Ge and Ni-Sn, all of which, however, have negative Hall coefficients over the e n t i r e c o n c e n t r a t i o n r a n g e so far investigated. A t h e o r e t i c a l explanation of positive Hall coeffic i e n t s in p u r e liquid t r a n s i t i o n m e t a l s is s t i l l
310
We would like to thank Prof. W. B a l t e n s p e r g e r , Dr. T. M. Rice and Miss A. ten Bosch for d i s c u s sion and Prof. J. Bass for reading the m a n u s c r i p t . We a r e indebted to the "Schweizerische Nationalfonds zur Ft}rderung der w i s s e n s c h a f t lichen F o r s c h u n g " and to the R e s e a r c h i n s t i t u t e of A l u s u i s s e , for f i n a n c i a l support.
References [1] G. Busch, H.-J. Gilntherodt, H.U. KIlnzi and L. Schlapbach, Phys. Letters 31A (1970)191, 32A (1970) 376; G. Busch, H. -J. Gtintherodt, H. U. KUnzi, H.A. Meier and L. Schlapbsch, Mat. Res. Bull 5 (1970) 567. [2] G. Busch and H. -J. Gt/ntherodt, Phys. kondens. Materie 6 (1967) 325. [3] W. Bsltensperger and A. ten Bosch, private communication (1970).