ELECTRONIC STRUCTURE AND MAGNETISM OF INTERFACES : SANDWICHES AND MODULATED STRUCTURES

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ELECTRONIC STRUCTURE AND MAGNETISM OF INTERFACES : SANDWICHES AND MODULATED

STRUCTURES

A. Freeman, Jian-Hua Xu, S. Ohnishi, T. Jarlborg

To cite this version:

A. Freeman, Jian-Hua Xu, S. Ohnishi, T. Jarlborg. ELECTRONIC STRUCTURE AND MAG-

NETISM OF INTERFACES : SANDWICHES AND MODULATED STRUCTURES. Journal de

Physique Colloques, 1984, 45 (C5), pp.C5-369-C5-370. �10.1051/jphyscol:1984556�. �jpa-00224174�

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JOURNAL DE PHYSIQUE

Colloque C5, supplCment a u n04, Tome 45, a v r i l 1984 page C5-369

ELECTRONIC STRUCTURE AND MAGNETISM OF INTERFACES : SANDWICHES AND MODULATED S T R U C T U R E S *

A.J. Freeman, J i a n - h u a X U + , S . O h n i s h i

++

and T . ~ a r l b o r g *

Physics Department and Materials Research Center, florthwestern U n i v e r s i t y , Evanston, I l l i n o i s 60201, U.S.A

.

* p h y s i c s Department, University o f Geneva, CH-1211 Geneva, Switzerland

Resume - I 1 e s t maintenant reconnu que l ' u n des developpements l e s p l u s im- p o r t a n t s pendant l a d e r n i e r e decade a 6 t e l a p r e p a r a t i o n de s t r u c t u r e s syn- t h k t i q u e s

a

une e c h e l l e i n f e r i e u r e au m i c r o n . L ' e x c i t a t i o n q u i e n t o u r e c e dPveloppement repose : s u r l a promesse de p r o d u c t i o n de m a t e r i a u x aux p r o - p r i e t e s d e s i r e e s p a r l a c a r a c t e r i s a t i o n , s u r l a p o s s i b i l i t e d ' a v o i r de nouveaux phenomenes s c i e n t i f i q u e s 8 e t u d i e r , s u r l ' o b t e n t i o n de d i s p o s i t i f s aux a p p l i c a t i o n s o r i g i n a l e s

a

l ' a i d e de m a t e r i a u x a r t i f i c i e l s , n ' e x i s t a n t pas dans l a n a t u r e ,

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s u r , en d ' a u t r e s mots, une i n d u s t r i e des m a t e r i a u x

a

l ' &

c h e l l e de m i c r o s t r u c t u r e s . Le domaine e t l a v a r i e t e des nouveaux phenomenes

a

P t u d i e r e s t un s t i m u l a n t d e f i . Comme exemples de ces m a t e r i a u x l ' e c h e l l e des m i c r o s t r u c t u r e s c i t o n s : l e s j o n c t i o n s de f i l m s minces de metaux d i f f e - r e n t s magn6tiques ou supraconducteurs, ou

...

^;e t l e s s t r u c t u r e s modulees (ABABA - - ) de deux m a t e r i a u x A e t B .

Dans ce resume, l e s r e s u l t a t s des etudes auto-coherentes de l a s t r u c t u r e de bande de t o u s l e s e l e c t r o n s

a

s p i n s p o l a r i s e s s o n t prGsent6s pour une j o n c - t i o n de f i l m s minces d'AgFe e t p o u r des s t r u c t u r e s modulees coherentes de CuNi e t PdAu. Dans l e cas de grandes m a i l l e s g l e m e n t a i r e s ( j u s q u ' a 12 couches) de CuNi, l e s m o d u l a t i o n s de longueurs d ' o n d e d i f f h r e n t e s l e l o n g des d i r e c t i o n s [l111 e t [l001 p r e d i s e n t une r e d u c t i o n des moments magnetiques des atomes de N i p a r r a p p o r t

a

l e u r v a l e u r dans l e N i c.f.c., sans t o u t e f o i s m o n t r e r d ' e v i d e n c e de "couche non magnetique" meme dans l e cas du systeme l e p l u s d i l u e . Les couches de Cu v o i s i n e s des couches de N i a c q u i e r e n t de p e t i t s moments magnetiques, mesurables p a r Resonance Magnetique N u c l e a i r e . Des e x h a l t a t i o n s accrues de l ' e c h a n g e s o n t mises en evidence dans PdAu e t d i s c u t e e s en r e l a t i o n avec l e s o b s e r v a t i o n s de Brodsky e t Freeman d ' u n e sus- c e p t i b i l i t e d'echange f o r t e m e n t e x h a l t e e dans l e s j o n c t i o n s de f i l m s minces de PdAu. Dans l e cas de AgFe, nous t r o u v o n s que 1 ' A g f a i t d e c r o i t r e beau- coup ( j u s q u ' a 2,95 v B ) , l e magnetisme e x h a l t @ observe s u r l a s u r f a c e l i b r e de Fe.

A b s t r a c t

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I t i s now r e c o g n i z e d t h a t o n e o f t h e most i m p o r t a n t developments i n t h e l a s t decade l i e s i n t h e p r e p a r a t i o n o f s y n t h e t i c s t r u c t u r e s on t h e submicron l e v e l . The e x c i t e m e n t s u r r o u n d i n g t h i s development l i e s i n t h e p r o - mise o f p r o d u c i n g m a t e r i a l s w i t h d e s i r e d p r o p e r t i e s t o s p e c i f i c a t i o n , o f p e r - m i t t i n g new s c i e n t i f i c phenomena t o be i n v e s t i g a t e d and novel d e v i c e a p p l i c a -

t i o n s t o be made on a r t i f i c i a l m a t e r i a l s n o t found i n n a t u r e

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i n o t h e r words, m a t e r i a l s e n g i n e e r i n g on t h e m i c r o s t r u c t u r e s c a l e . The range and va- r i e t y o f new phenomena t h a t can be s t u d i e d pose an e x c i t i n g c h a l l e n g e . Examples on t h e m i c r o s t r u c t u r e domain i n c l u d e t h i n f i lm j u n c t i o n s (sandwiches) o f d i s s i m i l a r m e t a l s which a r e e i t h e r magnetic o r superconducting e t c . , and modulated s t r u c t u r e s c o n s i s t i n g o f a l t e r n a t i n g l a y e r s o f m a t e r i a l s A and B, i . e . ABABA

--.

*supported by t h e NSF ( t h r o u g h t h e N . U . M a t e r i a l s R e s e a r c h C e n t e r )

:permanent a d d r e s s : Shanghai I n s t i t u t e o f M e t a l l u r g y , Shanghai200050, P.R. of China Permanent a d d r e s s : NEC, C o r p . , Kawasaki 213, Japan

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984556

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J O U R N A L DE PHYSIQUE

In t h i s paper, r e s u l t s of a l l - e l e c t r o n s e l f - c o n s i s t e n t spin-polarized band s t r u c t u r e s t u d i e s on a AgFe sandwich, and on CuNi and PdAu coherent modulated s t r u c t u r e s a r e presented. For CuNi, modulations along [ I l l ] and [ l 0 0 1 f o r d i f f e r e n t wave lengths and s u p e r c e l l s up t o 1 2 l a y e r s p r e d i c t Ni moments t o be reducedvs. f . c . c . N i , b u t n o "dead" l a y e r s even i n t h e most d i l u t e system.

Adjacent Cu l a y e r s acquire small magnetic moments, which may be measured by NMR. Increased exchange enhancements a r e found i n PdAu and discussed i n r e - l a t i o n t o t h e s t r o n g l y exchange enhanced s u s c e p t i b i l i t y observed i n PdAu sandwiches by Brodsky and Freeman. For AgFe we f i n d t h a t t h e Ag serves t o g r e a t l y decrease t h e enhanced magnetism ( t o 2.95 pB) found f o r t h e f r e e Fe s u r f a c e .