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NUCLEAR QUADRUPOLAR RELAXATION IN LIQUID Ga-Te ALLOYS
R. Brinkmann, M. Elwenspoek, M. von Hartrott, A. Novak, D. Quitmann
To cite this version:
R. Brinkmann, M. Elwenspoek, M. von Hartrott, A. Novak, D. Quitmann. NUCLEAR QUADRUPO-
LAR RELAXATION IN LIQUID Ga-Te ALLOYS. Journal de Physique Colloques, 1981, 42 (C4),
pp.C5-1055-C5-1058. �10.1051/jphyscol:19814231�. �jpa-00220862�
JOURNAL DE PHYSIQUE
CoZZoque C4, suppZe'ment au nOIO, Tome 42, octobre 1981 page (24-1055
NUCLEAR QUADRUPOLAR R E L A X A T I O N I N L I Q U I D Ga-Te ALLOYS
R. Brinkmann, M. Elwenspoek, M. von Hartrott
+ ,
A. Novak and D. QuitmannI n s t i t u t fur Atom- und Festkiiqerphysik, Freie U n i v e r s i t a t Berlin, 1000 Berlin 33, F. R. G.
A b s t r a c t . The n u c l e a r s p i n r e l a x a t i o n r a t e was measured i n l i q u i d GacTel-c a l l o y s on A s a s a n i m p u r i t y atom. A TDPAD t e c h n i q u e was u s e d o n t h e 6 u s 7 3 m ~ s i s o m e r . The r a n g e l,c,0.2 was s t u d i e d , w i t h T=1110 K f o r c c 0 . 7 . The q u a d r u p o l a r p a r t o f
t h e r a t e , RQ, was e x t r a c t e d . I t shows e s s e n t i a l l y t h e same c o n c e n t r a t i o n d e p e n d e n c e a s e x i s t i n g d a t a f o r
RQ
o f Ga i n l i q u i d Ga T e l - c , a n d c o r r e l a t e s s t r o n g l y w i t h t h e d i p i n conductivity C n e a r c = 0 . 4 . A q u a n t i t a t i v e a n a l y s i s o f t h e con- c e n t r a t i o n d e p e n d e n c e i s a t t e m p t e d u s i n g a s i m p l e m i c r o s c o p i c model. I t c o m p r i s e s l o c a l i z a t i o n o f c o n d u c t i o n e l e c t r o n si n c l u d i n g o n e f r e e p a r a m e t e r f o r c h a r g e s h i f t i n t h e Ga-Te bond ( i o n i c i t y ) . S a t i s f a c t o r y a g r e e m e n t i s o b t a i n e d .
Measurements o f t h e n u c l e a r s p i n r e l a x a t i o n r a t e R s h o u l d b e v e r y h e l p f u l i n u n d e r s t a n d i n g t h e m e t a l - s e m i c o n d u c t o r t r a n s i t i o n from a m i c r o s c o p i c p o i n t o f view. We r e p o r t h e r e on measurements o f t h e qua- d r u p o l a r r a t e R ( c ) o f As as a n i m p u r i t y atom i n l i q u i d GacTe
Q l - c '
which shows a s t r o n g c o r r e l a t i o n w i t h e l e c t r i c a l c o n d u c t i v i t y o ( c ) , a s h a s b e e n o b s e r v e d e a r l i e r f o r R o f Ga / l , 2 / . Warren / l , 2/ h a s
Q
s u g g e s t e d a c o n n e c t i o n o f t h e r i s e i n R n e a r c = 0.4 w i t h s l o w i n g Q
down o f t h e a t o m i c m o t i o n a n d c o v a l e n t b o n d i n g .
W e h a v e measured t h e n u c l e a r s p i n r e l a x a t i o n r a t e R = R +R Q M in l i q u i d GacTel-c, 1 c 2 0 . 2 , u s i n g 7 3 m ~ s ( 5 . 6 u s s t a t e ) a s t h e p r o b e n u c l e u s i n a TDPAD e x p e r i m e n t . D e t a i l s a b o u t t h e e x p e r i m e n t w i l l b e g i v e n i n a s u b s e q u e n t p u b l i c a t i o n / 3 / . The t e m p e r a t u r e was 1110 K e x c e p t f o r c = 1 , where T = 300 K . The m a g n e t i c c o n t r i b u t i o n RM c o u l d s a f e l y b e e s t i m a t e d from t h e measurement f o r 6 9 r 7 1 ~ a / 2 / . The r e s u l t s f o r R o f 7 3 m ~ s a r e p r e s e n t e d i n t h e f i g u r e . I t i s n o t e w o r t h y t h a t
Q
t h e y d i s p l a y t h e same s t r o n g c o n c e n t r a t i o n d e p e n d e n c e a s R o f Ga / 2 / , Q
i n s p i t e o f t h e c o n s i d e r a b l e c h e m i c a l d i f f e r e n c e between Ga and A s . The m o t i o n a l n a r r o w i n g r e s u l t f o r R i s R = c 0 n S t
-
< v ; ~ > - T2
Q
Qwhere < V 2 0 > ( ~ ) i s t h e mean s q u a r e f l u c t u a t i o n o f t h e e l e c t r i c f i e l d
+ G u e s t o f S f b 161
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19814231
C4- 1056 JOURNAL DE PHYSIQUE
g r a d i e n t a t t h e n u c l e u s ( e f g )
,
and T ( c ) i s t h e c o r r e l a t i o n t i m e of V 20- S i n c e we know o f no o t h e r s u i t a b l e d a t a a b o u t a t o m i c dynamics i n l i q u i d Ga-Te, R i s compared i n f i g . 1 w i t h v i s c o s i t y 0 from / 4 / . Though t h i sQ
e s t i m a t e o f t h e c o n c e n t r a t i o n dependence due t o T i s a d m i t t e d l y v e r y u n c e r t a i n , we c o n s i d e r it a r e a l i s t i c o r even (from l i q u i d m e t a l l i c a l l o y s ) upper e s t i m a t e f o r p o s s i b l e changes o f R ( c ) caused by T ( c ) .
Q
Now I- ( c = 0 . 4 ) / n ( l ) < < R (0.4 ) / R Q ( 1 1
,
and t h e t e m p e r a t u r e dependence ofQ
R n e a r c=0.4 /3/ i s a l s o d e f i n i t e l y s t r o n g e r t h a n t h a t o f n . We f e e l
Q 2
t h e r e f o r e f o r c e d t o t u r n t o t h e c o n c e n t r a t i o n dependence o f < V z 0 > and s h a l l a t t e m p t a q u a n t i t a t i v e e s t i m a t e o f t h e e f f e c t o f e l e c t r o n l o c a l i z a t i o n on it.
F o r t h e arrangement o f n e i g h b o u r atoms around t h e probe a model i n ?-space was u s e d , which r e p r o d u c e s r a t h e r w e l l t h e c a n c e l l a t i o n of two- and t h r e e p a r t i c l e t e r m s i n monatomic l i q u i d s / 3 / . The e f g pro- duced by a n e i g h b o u r i=Ga o r Te, VZoi i s d e r i v e d from a s c r e e n e d Coulomb p o t e n t i a l ,
I
l I II
100 80 60 4 0 20 0
at. % Ga
F i g . 1: C o n c e n t r a t i o n dependence o f q u a d r u p o l a r n u c l e a r s p i n r e l a x a t i o n r a t e
RQ
i n l i q u i d Ga,TelVc, n o r m a l i z e d a t c = l . P o i n t s a r e e x p e r i m e n t a l d a t a : A W a r r e n / 2 / , p r e s e n t work. F u l l c u r v e i s t h e model c a l c u l a t i o n d e s c r i b e d i n t h e t e x t ; t h e f r e e p a r a m e t e r i s .chosen a s 6 ion=O. 5. V i s c o s i t y q i s from / 4 / .A s i n an e a r l i e r n o t e we t h u s s t a r t from t h e m e t a l l i c l i q u i d s Ga,Te / 5 / . A s a f i r s t a p p r o x i m a t i o n , t h e c o n c e n t r a t i o n dependence o f t h e e f f e c t i v e S t e r n h e i m e r f a c t o r i s n e g l e c t e d . The d e n s i t y o f " f r e e 1 ' e l e c t r o n s , n cond
,
d e t e r m i n e s t h e c o n d u c t i v i t y o , and a l s o t h e s h i e l d i n g l e n g t h a c c o r d i n g t o = m e 2 h - 2 ( 3 / a .ncond)'I3.
The number o f f r e e e l e c t r o n s i s 3/atom i n Ga. For Te, i t i s t a k e n fromsail
and U t o b e a l s o c l o s e t o 3 above l 0 0 0 K , s e e / 6 / . Thusz;zn
=zion
= +3 and n cond =Te 3 / v i n
t h e p u r e l i q u i d s , v = a t o m i c volume ( v Te + vGa)
.
Comparing a N F E ( ~ )-
o b t a i n e d by i n t e r p o l a t i n g 1/uGa, l/oTe
-
w i t h t h e e x p e r i m e n t a l o ( c ) one o b t a i n sn cond =
3/v
.
o ( c ) / o N F E ( c )-
The a v e r a g e number o f l o c a l i z e d e l e c t r o n s p e r c e l l ,
z l o c
= 3-n cond.
v i s now a s s i g n e d t o Ga o r Te c e l l s where t h e i r c h a r g e adds t o z:On:-
Z i - Z i o n ~ Z l o c ~ Z l o c i
,
Ga andzfZC
can be t h o u g h t o f a s composed o f a p a r t symmetric w i t h r e s p e c t t o Ga o r Te, and an asymmetric p a r t , and t h e former may b e i d e n t i f i e d w i t h bonding o f c o v a l e n t , t h e l a t t e r w i t h i o n i c c h a r a c t e r . The c o r r e s p o n d i n g p a r a m e t e r G i o n ( O ~ G i o n ~ l ) i s norma- l i z e d s u c h t h a t i f a t t h e 2:3 c o m p o s i t i o n f u l l l o c a l i z a t i o n o c c u r e d( z l o c
= 3 ) w i t h 100% i o n i c i t y(aion
= l ) , t h e n t h e l o c a l i z e d e l e c t r o n s would a l l b e found i n t h e Te c e l l sT h i s r e l a t i o n and t h e r e q u i r e m e n t o f c h a r g e n e u t r a l i t y , c ZGa+(l-c)ZTe
= n Cond.v, f i x
z,?.ZC
and ZTe l o c.
<V20> 2 ( C ) can t h e n be c a l c u l a t e d f o r g i v e n c , o ( c ) and G i o n . I t i s t h e d i f f e r e n c e o f c h a r g e s ZGa-Z % G i o n which p r o d u c e s a d i f f e r e n c e
Te
i n e f g ' s , t h e s e b e i n g s t r o n g l y enhanced around c = 0.4 by t h e d e c r e a s e i n A . A l a r g e <V20> r e s u l t s from t h e r e w h i l e i n t h e p r e s e n t t r e a t m e n t 2 t h e symmetric p a r t o f z:Oc c o n t r i b u t e s l i t t l e t o < V Z O > 2 around c = 0 . 4 .
( A l a r g e d i f f e r e n c e i n e f g ' s may, however, a l s o be a s c r i b e d t o co- v a l e n t bonding o f t h e p r o b e atom p r e d o m i n a n t l y t o one k i n d of n e i g h - b o u r s . ) A s d i s c u s s e d above, we u s e n ( c ) t o e s t i m a t e r ( c ) . The d a t a used a r e f o r 1110 K e x e p t f o r t h e n o r m a l i z a t i o n p o i n t a t c = 1 where t h e y a r e f o r 300 K .
The f u l l c u r v e i n f i g . 1 i s R ( c ) / R ( c = l ) f o r a v a l u e o f t h e
Q Q
s i n g l e f r e e p a r a m e t e r Gion = 0 . 5 ( i n d e p e n d e n t o f c ) . Though t h e r e a r e d i s c r e p a n c i e s i n d e t a i l , t h e o v e r a l l agreement o f t h e p r e s e n t v e r y
C4- 1058 JOURNAL DE PHYSIQUE
s i m p l e model w i t h e x p e r i m e n t o v e r t h e f u l l c o n c e n t r a t i o n r a n g e i s e n c o u r a g i n g . The t e m p e r a t u r e dependence i s a l s o s a t i s f a c t o r i l y e x p l a i n e d : f o r t h e s e d a t a and an e x t e n d e d r e p o r t s e e / 3 / .
The a u t h o r s are o b l i g e d t o D e u t s c h e F o r s c h u n g s g e m e i n s c h a f t , S f b 161, f o r f i n a n c i a l s u p p o r t , and t o G e s e l l s c h a f t f u r K e r n f o r s c h u n g , K a r l s - r u h e , f o r machine t i m e a t t h e c y c l o t r o n .
Ref e r e n c e s
l WARREN W.W. Jr. :Phys. Rev. ( 1 9 7 1 ) 3708
/ 2 / WARREN W.W. Jr.: J. Non-Cryst. S o l i d s
8-10
( 1 9 7 2 ) 241/ 3 / BRINKMANN R , ELWENSPOEK M.
,
von HARTROTT M . , NOVAK A . , and QUITMANN D.: t o b e p u b l i s h e d/ 4 / GLAZOV V.M., CHIZHEVSKAYA S.N. and GLAGOLEVA N . N . : L i q u i d Semi-
c o n d u c t o r s , Plenum, New York 1969
/5/ HbHNE J . , von HARTROTT M., QUITMANN D.,ROSSBACH J . , WEIHRETER E . , WILLEKE F . and SCHIRMACHER W . : P r o c 7 t h I n t . Conf. on Am. and L i q . S e m i c o n d u c t o r s , Univ. o f Edinburgh 1977, p. 848; I n s t . Phys. Conf.
S e r i e s
30
( 1 9 7 7 ) 460/ 6 / MOTT N.F. and DAVIS E.A.: E l e c t r o n i c P r o c e s s e s i n N o n - C r y s t a l l i n e M a t e r i a l s C l a r e n d o n . Oxford 1971
