Superconductivity and physical metallurgy
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Superconductivity and Physical Metallurgy
ALFRED SEEGER
A f t e r a b r i e f s u m m a r y of the h i s t o r i c a l d e v e l o p m e n t of the f i e l d of s u p e r c o n d u c t i v i t y and the b a c k g r o u n d r e q u i r e d for the topics t r e a t e d in the p r e s e n t p a p e r , s o m e of the r e l a t i o n s h i p s between s u p e r c o n d u c t i v i t y and p h y s i c a l m e t a l l u r g y a r e d i s c u s s e d . T h e s e a r e m a i n l y in two a r e a s : i) The d i s t r i b u t i o n of m a g n e t i c flux in s u p e r c o n d u c t o r s m a y show fine s t r u c t u r e s (boundaries b e t w e e n n o r m a l and s u p e r c o n d u c t i n g r e g i o n s in the i n t e r m e d i a t e state of t y p e - I s u p e r c o n d u c t o r s ; q u a n t i z e d f l u x - l i n e s in the Shubnikov phase of t y p e - I I s u p e r c o n d u c t o r s ) on such a scale that they i n t e r a c t s t r o n g l y with the m e t a l l u r g i c a l m i c r o s t r u c t u r e of the s u p e r conducting m a t e r i a l s , such as g r a i n b o u n d a r i e s , d i s l o c a t i o n s , p r e c i p i t a t e s , and so forth. ii) Ideally, the f l u x - l i n e s in a t y p e - ] / s u p e r c o n d u c t o r f o r m a t w o - d i m e n s i o n a l lattice (Abrikosov lattice). The d e c o r a t i o n technique of TrOuble and E s s m a n n has p e r m i t t e d the d i r e c t o b s e r v a t i o n of t h e s e f l u x - l i n e s l a t t i c e s and h a s r e v e a l e d that they c o n t a i n a r a t h e r high d e n sity of defects. Most of t h e m a r e known f r o m the s t u d i e s of d e f e c t s in c r y s t a l s , such a s g r a i n b o u n d a r i e s , d i s l o c a t i o n s , s t a c k i n g f a u l t s , and v a c a n c y and i n t e r s t i t i a l l i n e s , but also d i s c l i n a t i o n s , which were p r e d i c t e d by t h e o r y but have not yet been o b s e r v e d in m e t a l s , were i n v e s t i gated. W H E N I was i n f o r m e d that I had been chosen a s the I n s t i t u t e of Metals D i v i s i o n L e c t u r e r for the y e a r of 1970, I t r i e d to envisage what kind of l e c t u r e was expected f r o m m e . I do not know those who proposed and e l e c t e d m e , so I could not a s k t h e m . Since I expect that at l e a s t some of them a r e in the a u d i e n c e , I should like to take this opportunity to e x p r e s s my s i n c e r e g r a t i t u d e to t h e m . I a m all the m o r e g r a t e f u l for this h o n o r , s i n c e I noted f r o m the list of p r e v i o u s l e c t u r e r s that I s h a l l be the f i r s t l e c t u r e r c o m i n g f r o m G e r m a n y s i n c e the y e a r of 1933. In that y e a r , which was p e r n i c i o u s to G e r m a n s c i e n c e and indeed to m a n k i n d , the v e n e r a t e d late G e o r g Masing d e l i v e r e d the l e c t u r e on P r e s e n t Day P r o b l e m s in T h e o r e t i c a l M e t a l l u r g y . When going through the list of p r e v i o u s l e c t u
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