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Low temperature recovery in cold worked f.c.c. metals
Volume 25A, number 3
PHYSICS LETTERS
a r i s e s f r o m holes in a v a l e n c e band. A d e c r e a s e of the n u m b e r of holes, i.e. a d e c r e a s e of the density of s t a t e s , is expected in the t e r n a r y s y s t e m CuRh2.xTixS 4 (with x < 1) for i n c r e a s i n g v a l u e s of x, so that a d e c r e a s e of the t r a n s i t i o n t e m p e r a t u r e may be expected a c c o r d i n g to the BCS theory. E x p e r i m e n t a l l y we o b s e r v e d a d e c r e a s e of 1.8°K for x = 0.10. Magnetic ions can be i n c o r p o r a t e d by p r e p a r ing m i x e d c r y s t a l s of CuRh2S4 with e.g. CoRh2S4 [5] (ao = 9.78A) or C u C r 2 S 4 [6] (ao = 9.82A). The superconductivity in both types of mixed crystals was found to be strongly influenced. The transition temperature was lowered by about 1.0°K for Cu0.98 Co0.02Rh2S4 and by about 0.9°K for CuRh1.992Cr0.008S 4. These results have to be considered, however, as a first ap-
14 August 1967
p r o a c h only. In both c a s e s we o b s e r v e d a f a i r l y b r o a d t r a n s i t i o n , which probably a r i s e s from an inhomogeneous d i s t r i b u t i o n of the s m a l l a m o u n t s of Co and Cr.
Referen. ces 1. G. Blasse and D.J. Schipper, J. Inorg. Nucl. Chem. 26 (1964) 1467. 2. F.K. Lotgering and R. P. van Stapele, Solid State Comm. 5 (1967) 143. 3. R.J. Bouchard, P. A. Russo and A. Wold, Inorg. Chem. 4 (1965) 685. 4. G. Blasse, see ref. 2. 5. G. Blasse, Phys. Letters 19 (1965) 110. 6. F.K. Lotgering, Proc. Int. Conf. on Magnetism, Nottingham 1964, p. 533. $
LOW TEMPERATURE
RECOVERY
IN COLD
WORKED
f.c.c.
METALS
S. OKUDA and S. TAKAMURA Japan Atomic Energy Research Institute, Tokai-mura, Ibaraki, Japan Received 29 June 1967
Initial continuous recovery in resistivityobserved in f.c.c, metals after cold work at 4.20K is discussed and attributed to the dislocation rearrangement.
Although i n t e r p r e t a t i o n s of r e c o v e r y stages a f t e r cold work of f.c.c, m e t a l s b a s e d on the c o m p a r i s o n with those a f t e r i r r a d i a t i o n and quenching a r e made in a s u c c e s s f u l way [1,2], r e covery stages in the s a m e t e m p e r a t u r e r a n g e s a f t e r different t r e a t m e n t s would s o m e t i m e s be a s s o c i a t e d with a n n e a l i n g of different kinds of d e fects. F o r example, Cuddy [3] has shown that the r e c o v e r y of i r o n a f t e r cold work at 77°K could p o s s i b l y be a t t r i b u t e d to dislocation r e c o v e r y . The p u r p o s e of this r e p o r t is to p r o p o s e that the dislocation r e a r r a n g e m e n t could be r e s p o n s i b l e for the i n i t i a l r e c o v e r y stage of f.c.c, m e t a l s a f t e r cold work at 4.2°K. E l e c t r i c a l r e s i s t i v i t y of 99.999% p u r e gold w i r e s were m e a s u r e d at 4.2°K a f t e r t e n s i l e d e f o r m a t i o n at 4.2°K and s u b s e q u e n t i s o c h r o n a l a n n e a l i n g . The d e t a i l s of the e x p e r i m e n t a l r e s u l t s will be published e l s e w h e r e . Fig. 1 shows r e covery c u r v e s a f t e r v a r i o u s t r e a t m e n t s . F o r the fully a n n e a l e d f i r s t s p e c i m e n , the r e s i s t i v i t y
showed continuous d e c r e a s e up to 120°K and the r e v e r s e a n n e a l i n g in 120 ° - 150°K in good a g r e e m e n t with the r e s u l t s by S c h u m a c h e r and Seeger [4]. F o r the t h i r d s p e c i m e n with the l a r g e s t i n i t i a l dislocation density, the i n i t i a l continuous r e covery was o b s e r v e d with a much l a r g e r slope. It can be seen f r o m the r e s u l t s of ref. 4 that the p e r c e n t r e c o v e r y up to 120°K r e m a i n e d a l m o s t c o n s t a n t for different d e g r e e s of d e f o r m a t i o n at 4.2°K. P r e s e n t r e s u l t s showed that the i n c r e a s e in dislocation d e n s i t y before d e f o r m a t i o n at 4.2°K i n c r e a s e d this p e r c e n t r e c o v e r y up to 120°K m o r e than twice. This suggests that the d i s l o c a tion r e a r r a n g e m e n t may be a s s o c i a t e d with this recovery because a larger dislocation r e a r r a n g e m e n t could be expected for the s p e c i m e n with a l a r g e r d i s l o c a t i o n density. T h i s cannot be expected by the a n n i h i l a t i o n of c o r r e l a t e d i n t e r s t i t i a l v a c a n c y p a i r s suggested in ref. 4. The expected n u m b e r of the I - V p a i r s would also be too s m a l l to account for the o b s e r v e d amount of the r e c o v e r y 239
Volume 25A, number 3
PHYSICS LETTERS
Temp 0
50
I- xlO-lJ~crn
in ° K
I O0
150
200
'
,
,
\
,.= \
\
Ae
Au
Fig. 1. Isochronal recovery curves of 99.999% gold cold worked at 4.2°K. Resistivity was measured at 4.2OK after each pulse (6 minutes) annealing. Total resistivity increase ~Ap). ratio of resistivity at room temperature and at 4.2VK before deformation at 4.2°K (Dr.t./P4 2), and elongation (~) were indicated. Pre-deformatioh" states of the specimens were as follows: cold drawn wires as received were; 1, annealed at 890°C in air i.e. in fully annealed state (A); 2, annealed at 600°C(O); 3, annealed at 600°C, cold drawn 19% in reduction of area, then annealed at 100°C in order to anneal out only point defects ( V , ~ ) . [5]. T h e continuous n a t u r e of the r e c o v e r y at l e a s t up to 120°K i s p a r t i c u l a r l y a p p r o p r i a t e to the d i s l o c a t i o n r e a r r a n g e m e n t .
240
14 August 1967
F o r the f i r s t s p e c i m e n , if we a s s u m e one half of the Ap was due to d i s l o c a t i o n s [1], the r e s i s tivity due to d i s l o c a t i o n s ,xp D r e c o v e r e d only l e s s than 2% up to 120°K. F o r the t h i r d s p e c i m e n , if we u se PD = 3.5 x 10 -19 ~ c m 3 / d i s l . (for gold) [2], the i n i t i a l d i s l o c a t i o n density was about 5 x x 1010/cm2,u, and ApD r e c o v e r e d by about 4% up to 120 K or 6% up to 150 K. T h e r e f o r e , even if we a s s u m e that the r e c o v e r y in t h e s e t e m p e r a t u r e s (initial continuous r e c o v e r y ) would have been s o l e l y due to the r e d u c t i o n of the d i s l o c a t i o n d e n sity, the d i s l o c a t i o n density would have d e c r e a s ed by l e s s than s e v e r a l p e r c e n t which would not be u n r e a s o n a b l e . D u r i n g the r e a r r a n g e m e n t of d i s l o c a t i o n s s o m e point d e f e c t s m ay a l s o be a b s o r b e d by m o v i n g d i s l o c a t i o n s . R e c o v e r y of i n t e r n a l f r i c t i o n at low t e m p e r a t u r e s a l s o showed a d i s l o c a t i o n r e a r r a n g e m e n t at t h e s e low t e m p e r a t u r e s in the s p e c i m e n d e f o r m e d at 4.2°K [6]. F u r t h e r m o r e , in the c o u r s e of the i n t e r n a l f r i c t i o n e x p e r i m e n t s [6], it was o b s e r v e d that the s p e c i m e n w i r e d e f o r m e d by t o r s i o n at 4.2°K in one d i r e c t i o n , untwisted continuously in a n o t h e r d i r e c t i o n d u r i n g w a r m - u p through t h e s e t e m p e r a t u r e s . T h i s would p r o v i d e a d i r e c t e v i dence f o r the d i s l o c a t i o n r e a r r a n g e m e n t . T h e r e f o r e , the i n i t i al continuous r e c o v e r y o b s e r v e d in f . c . c , m e t a l s cold worked at 4.2°K [4,5,7,8] could b e s t be explained by the d i s l o c a t i o n r e arrangement. The a u t h o r s would like to thank P r o f . J. T a k a m u r a and D r . H. S a k a i r i f o r t h e i r v a l u a b l e d i s cussions. 1. H.G. van Bueren, Imperfections in crystals (NorthHolland Publ. Comp., Amsterdam, 1961). 2. J. Friedel, Dislocations (Pergamon Press, London, 1964). 3. L . J . Cuddy, Phil. Mag. 12 (1965)855. 4. D.Schumacher and A.Seeger, Phys. Letters 7 (1963) 184. 5. H.I.Dawson, Physica 31 (1965) 1046. 6. S.Okuda, J. Appl. Phys. 34 (1963) 3107; Sci. Papers I.P.C.R., 57 (1963) 116. 7. C.J.Meechan and A.Sosin, J. Appl. Phys. 29 (1958) 738. 8. M.L.Swanson, Canadian J. Phys. 42 (1964)1890.
PHYSICS LETTERS
a r i s e s f r o m holes in a v a l e n c e band. A d e c r e a s e of the n u m b e r of holes, i.e. a d e c r e a s e of the density of s t a t e s , is expected in the t e r n a r y s y s t e m CuRh2.xTixS 4 (with x < 1) for i n c r e a s i n g v a l u e s of x, so that a d e c r e a s e of the t r a n s i t i o n t e m p e r a t u r e may be expected a c c o r d i n g to the BCS theory. E x p e r i m e n t a l l y we o b s e r v e d a d e c r e a s e of 1.8°K for x = 0.10. Magnetic ions can be i n c o r p o r a t e d by p r e p a r ing m i x e d c r y s t a l s of CuRh2S4 with e.g. CoRh2S4 [5] (ao = 9.78A) or C u C r 2 S 4 [6] (ao = 9.82A). The superconductivity in both types of mixed crystals was found to be strongly influenced. The transition temperature was lowered by about 1.0°K for Cu0.98 Co0.02Rh2S4 and by about 0.9°K for CuRh1.992Cr0.008S 4. These results have to be considered, however, as a first ap-
14 August 1967
p r o a c h only. In both c a s e s we o b s e r v e d a f a i r l y b r o a d t r a n s i t i o n , which probably a r i s e s from an inhomogeneous d i s t r i b u t i o n of the s m a l l a m o u n t s of Co and Cr.
Referen. ces 1. G. Blasse and D.J. Schipper, J. Inorg. Nucl. Chem. 26 (1964) 1467. 2. F.K. Lotgering and R. P. van Stapele, Solid State Comm. 5 (1967) 143. 3. R.J. Bouchard, P. A. Russo and A. Wold, Inorg. Chem. 4 (1965) 685. 4. G. Blasse, see ref. 2. 5. G. Blasse, Phys. Letters 19 (1965) 110. 6. F.K. Lotgering, Proc. Int. Conf. on Magnetism, Nottingham 1964, p. 533. $
LOW TEMPERATURE
RECOVERY
IN COLD
WORKED
f.c.c.
METALS
S. OKUDA and S. TAKAMURA Japan Atomic Energy Research Institute, Tokai-mura, Ibaraki, Japan Received 29 June 1967
Initial continuous recovery in resistivityobserved in f.c.c, metals after cold work at 4.20K is discussed and attributed to the dislocation rearrangement.
Although i n t e r p r e t a t i o n s of r e c o v e r y stages a f t e r cold work of f.c.c, m e t a l s b a s e d on the c o m p a r i s o n with those a f t e r i r r a d i a t i o n and quenching a r e made in a s u c c e s s f u l way [1,2], r e covery stages in the s a m e t e m p e r a t u r e r a n g e s a f t e r different t r e a t m e n t s would s o m e t i m e s be a s s o c i a t e d with a n n e a l i n g of different kinds of d e fects. F o r example, Cuddy [3] has shown that the r e c o v e r y of i r o n a f t e r cold work at 77°K could p o s s i b l y be a t t r i b u t e d to dislocation r e c o v e r y . The p u r p o s e of this r e p o r t is to p r o p o s e that the dislocation r e a r r a n g e m e n t could be r e s p o n s i b l e for the i n i t i a l r e c o v e r y stage of f.c.c, m e t a l s a f t e r cold work at 4.2°K. E l e c t r i c a l r e s i s t i v i t y of 99.999% p u r e gold w i r e s were m e a s u r e d at 4.2°K a f t e r t e n s i l e d e f o r m a t i o n at 4.2°K and s u b s e q u e n t i s o c h r o n a l a n n e a l i n g . The d e t a i l s of the e x p e r i m e n t a l r e s u l t s will be published e l s e w h e r e . Fig. 1 shows r e covery c u r v e s a f t e r v a r i o u s t r e a t m e n t s . F o r the fully a n n e a l e d f i r s t s p e c i m e n , the r e s i s t i v i t y
showed continuous d e c r e a s e up to 120°K and the r e v e r s e a n n e a l i n g in 120 ° - 150°K in good a g r e e m e n t with the r e s u l t s by S c h u m a c h e r and Seeger [4]. F o r the t h i r d s p e c i m e n with the l a r g e s t i n i t i a l dislocation density, the i n i t i a l continuous r e covery was o b s e r v e d with a much l a r g e r slope. It can be seen f r o m the r e s u l t s of ref. 4 that the p e r c e n t r e c o v e r y up to 120°K r e m a i n e d a l m o s t c o n s t a n t for different d e g r e e s of d e f o r m a t i o n at 4.2°K. P r e s e n t r e s u l t s showed that the i n c r e a s e in dislocation d e n s i t y before d e f o r m a t i o n at 4.2°K i n c r e a s e d this p e r c e n t r e c o v e r y up to 120°K m o r e than twice. This suggests that the d i s l o c a tion r e a r r a n g e m e n t may be a s s o c i a t e d with this recovery because a larger dislocation r e a r r a n g e m e n t could be expected for the s p e c i m e n with a l a r g e r d i s l o c a t i o n density. T h i s cannot be expected by the a n n i h i l a t i o n of c o r r e l a t e d i n t e r s t i t i a l v a c a n c y p a i r s suggested in ref. 4. The expected n u m b e r of the I - V p a i r s would also be too s m a l l to account for the o b s e r v e d amount of the r e c o v e r y 239
Volume 25A, number 3
PHYSICS LETTERS
Temp 0
50
I- xlO-lJ~crn
in ° K
I O0
150
200
'
,
,
\
,.= \
\
Ae
Au
Fig. 1. Isochronal recovery curves of 99.999% gold cold worked at 4.2°K. Resistivity was measured at 4.2OK after each pulse (6 minutes) annealing. Total resistivity increase ~Ap). ratio of resistivity at room temperature and at 4.2VK before deformation at 4.2°K (Dr.t./P4 2), and elongation (~) were indicated. Pre-deformatioh" states of the specimens were as follows: cold drawn wires as received were; 1, annealed at 890°C in air i.e. in fully annealed state (A); 2, annealed at 600°C(O); 3, annealed at 600°C, cold drawn 19% in reduction of area, then annealed at 100°C in order to anneal out only point defects ( V , ~ ) . [5]. T h e continuous n a t u r e of the r e c o v e r y at l e a s t up to 120°K i s p a r t i c u l a r l y a p p r o p r i a t e to the d i s l o c a t i o n r e a r r a n g e m e n t .
240
14 August 1967
F o r the f i r s t s p e c i m e n , if we a s s u m e one half of the Ap was due to d i s l o c a t i o n s [1], the r e s i s tivity due to d i s l o c a t i o n s ,xp D r e c o v e r e d only l e s s than 2% up to 120°K. F o r the t h i r d s p e c i m e n , if we u se PD = 3.5 x 10 -19 ~ c m 3 / d i s l . (for gold) [2], the i n i t i a l d i s l o c a t i o n density was about 5 x x 1010/cm2,u, and ApD r e c o v e r e d by about 4% up to 120 K or 6% up to 150 K. T h e r e f o r e , even if we a s s u m e that the r e c o v e r y in t h e s e t e m p e r a t u r e s (initial continuous r e c o v e r y ) would have been s o l e l y due to the r e d u c t i o n of the d i s l o c a t i o n d e n sity, the d i s l o c a t i o n density would have d e c r e a s ed by l e s s than s e v e r a l p e r c e n t which would not be u n r e a s o n a b l e . D u r i n g the r e a r r a n g e m e n t of d i s l o c a t i o n s s o m e point d e f e c t s m ay a l s o be a b s o r b e d by m o v i n g d i s l o c a t i o n s . R e c o v e r y of i n t e r n a l f r i c t i o n at low t e m p e r a t u r e s a l s o showed a d i s l o c a t i o n r e a r r a n g e m e n t at t h e s e low t e m p e r a t u r e s in the s p e c i m e n d e f o r m e d at 4.2°K [6]. F u r t h e r m o r e , in the c o u r s e of the i n t e r n a l f r i c t i o n e x p e r i m e n t s [6], it was o b s e r v e d that the s p e c i m e n w i r e d e f o r m e d by t o r s i o n at 4.2°K in one d i r e c t i o n , untwisted continuously in a n o t h e r d i r e c t i o n d u r i n g w a r m - u p through t h e s e t e m p e r a t u r e s . T h i s would p r o v i d e a d i r e c t e v i dence f o r the d i s l o c a t i o n r e a r r a n g e m e n t . T h e r e f o r e , the i n i t i al continuous r e c o v e r y o b s e r v e d in f . c . c , m e t a l s cold worked at 4.2°K [4,5,7,8] could b e s t be explained by the d i s l o c a t i o n r e arrangement. The a u t h o r s would like to thank P r o f . J. T a k a m u r a and D r . H. S a k a i r i f o r t h e i r v a l u a b l e d i s cussions. 1. H.G. van Bueren, Imperfections in crystals (NorthHolland Publ. Comp., Amsterdam, 1961). 2. J. Friedel, Dislocations (Pergamon Press, London, 1964). 3. L . J . Cuddy, Phil. Mag. 12 (1965)855. 4. D.Schumacher and A.Seeger, Phys. Letters 7 (1963) 184. 5. H.I.Dawson, Physica 31 (1965) 1046. 6. S.Okuda, J. Appl. Phys. 34 (1963) 3107; Sci. Papers I.P.C.R., 57 (1963) 116. 7. C.J.Meechan and A.Sosin, J. Appl. Phys. 29 (1958) 738. 8. M.L.Swanson, Canadian J. Phys. 42 (1964)1890.