Magnetic hyperfine structure in 125Te

Volume 26A, number 10

MAGNETIC

PHYSICS LETTERS

HYPERFINE

8April 1968

STRUCTURE

IN

125Te

R. B. F R A N K E L *, J . J . HUNTZICKER, D . A . SHIRLEY and N. J. STONE ** Department of Chemistry and Lawrence Radiation Laboratory, University of California, Berkeley, California, USA Received 5 February 1968

Mi~ssbauer spectra of 125TeFe with improved resolution yield /1(35.5 keV) = +0.60 + 0.02 nm. The effect of this value on hyperfine spectra of 125Te are discussed.

H y p er f i n e s t r u c t u r e f o r 125Te in f e r r o m a g netic m e t a l s has been r e p o r t e d b e f o r e [1,2], but no a c c u r a t e v al u e has bee~ r e p o r t e d f o r the m a g netic m o m e n t of the f i r s t e x c i te d state, of spin ~, at 35.5 keV. This magnetic m o m e n t is difficult to m e a s u r e b e c a u s e the line widths of the h y p e r fine components a r e l a r g e r than the e x c i t e d st a te splitting, even in T e F e , the m o s t f a v o r a b l e c a s e known. R e c e n t l y U l l r i c h and Vincent r e p o r t e d [3] a magnetic h y p e r f i n e f i e l d f o r C u C r 2 T e 4 of 148 kOe and a m a g n e t i c m o m e n t of +0.74 :~ 0.07 nm f o r #(35.5). T h e s e two p a r a m e t e r s w e r e d e r i v e d s i m u l t a n e o u s l y by fitting the M ~ s s b a u e r s p e c t r u m of 125Te in C u C r 2 T e 4 , and a r e t h e r e f o r e r e l a t e d . We have made a c a r e f u l study of the s p e c t r u m of 125Te in TeF___ee, using a s o u r c e of 125SbF__e_eand a ZnTe a b s o r b e r , and have d e r i v e d the v a l u e #(35.5) = +0.60 =~0.02 for the e x c i t e d - s t a t e moment. S e v e r a l studies of the 125Te s p e c t r u m have been made s i n c e our e a r l i e r work [2] with the goal of r e s o l v i n g the h y p e r f i n e components. The b e s t r e s u l t s to date a r e shown in fig. 1. The evidence for a s i x - l i n e h y p e r f i n e s p e c t r u m with r e l a t i v e i n t e n s i t i e s 3:2:1:1:2:3 is much m o r e c o m pelling than in o t h er published s p e c t r a [1-3]. In this e x p e r i m e n t the s o u r c e of 125Sb in i r o n was p r e p a r e d by e l e c t r o p l a t i n g the 125Sb f r o m 3N HC1 solution onto 99.99% F e foil. The foil was m e l t e d at 1550°C and quenched to r o o m t e m p e r a t u r e . A f t e r the r e s u l t i n g ingot was pounded to s e v e r a l thousandths of an inch t h i c k n e s s , it was annealed at 830°C f o r four h o u r s and at 700°C for one hour. The a b s o r b e r was e n r i c h e d ZnTe * Present address: Technische Hoehschule Mtlnchen, Munich, West Germany. ** Present address: Clarendon Laboratory, Oxford University, Oxford, England. 452

i

i

125Te in Fe

190

185

_4'

i

i

.~ ~ ~ Doppler Velocity(¢m/sec)

.

i

Fig. 1. Mi~ssbauer hyperfine spectrum for 125TeFe with a ZnTe absorber. p r e p a r e d by d i r e c t r e a c t i o n of the e l e m e n t s at 800°C in an H 2 a t m o s p h e r e and c a r e f u l l y s e a l e d to avoid r e a c t i o n with w at er vapor. The linewidth of this a b s o r b e r a g a i n s t a 125TeC__uu s o u r c e was 0.71 c m / s e c . The m i n i m u m t h e o r e t i c a l l y p o s s i b l e is 0.50(3) c m / s e c . A Ge(Li) d e t e c t o r with 3 keV r e s o l u t i o n allowed us to o b s e r v e a m a x i m u m ab s o r p t i o n of about 3% with the 125SbFe s o u r c e . Th e linewidth with this s o u r c e was 0.98 c m / s e c . A l e a s t - s q u a r e s fit of the s p e c t r u m in fig. 1 gave U(35.5)/#(0) = - 0.678. Combining this with the known g r o u n d - s t a t e m o m e n t /1(0) = -0.8872 n m [ 4 ] , we have ~(35.5) = + 0 . 6 0 ± 0 . 0 2 . This is in v e r y good a g r e e m e n t with the v a l u e s d e r i v e d f r o m s e v e r a l other s p e c t r a , and we su g g est that this v al u e be adopted f o r analyzing p a r t i a l l y - r e s o l v e d hfs s p e c t r a of 125Te. C o m p a r i s o n with the C u C r 2 T e 4 s p e c t r u m r e p o r t e d by U l l r i c h and Vincent s u g g e s t s that c o n s t r a i n i n g /~(35.5) to + 0.60 nm would r a i s e t h e i r d e r i v e d Hhf to about

Volume 26A, n u m b e r 10

PHYSICS

160 k O e , i n b e t t e r a g r e e m e n t w i t h t h e N M R v a l u e of B u d n i c k e t a l . [8]. F r o m s p e c t r a of 125Sb in F e , Co, a n d Ni a t 4 . 2 ° K w e f i n d , u s i n g t h i s m o m e n t , H h f ( 1 2 5 T e F e ) = + 6 5 7 + 20 k O e I H h g ( 1 2 5 T e C o ) I = 505 ± 20 k O e , a n d Hhf(-125TeNi~-=- + 170 + 10 k O e , i n r e a s o n a b l e a g r e e m e n t w i t h o u r e a r l i e r v a l u e s f o r F e a n d Ni. Finally, Kisslinger and Sorensen have pred i c t e d [6], t h a t t h i s s t a t e h a s m o s t l y d ~ - p r o t o n quasiparticle character, with small admixtures of q u a s i p a r t i c l e - p l u s - p h o n o n c h a r a c t e r . T h e y c a l c u l a t e d m a g n e t i c m o m e n t s of + 0 . 5 6 if t h e

THE

LOW

TEMPERATURE FOLLOWING

LETTERS

8 A p r i l 1968

p h o n o n gR i s z e r o o r + 0 . 6 4 if gR = Z / A . E i t h e r of t h e s e i s i n e x c e l l e n t a g r e e m e n t w i t h o u r r e s u l t . 1. N. Shikazono, J. Phys. Soc. Japan 18 (1963) 925. 2. R.B. Frankel, J. Huntzicker, E. Matthias, S.S. Rosenblum, D.A. Shirley and N. J. Stone, Phys. L e t t e r s 15 (1965) 163. 3. J. F. Ullrich and D. H. Vincent, Phys. L e t t e r s 25A (1967) 731. 4. H . E . W e a v e r J r . , Phys. Rev. 89 (1953)923. 5. S. B e r g e r , J . I . Budnick and T. J. Burch, Phys. Lett e r s 26A (1968) 450. 6. L.S. K i s s l i n g e r and R. A. Sorensen, Rev. Mod. Phys. 35 (1963) 853.

ANNEALING ELECTRON

SPECTRUM IRRADIATION

OF *

MAGNESIUM

T . N. O ' N E A L a n d R. L. C H A P L I N Department of Physics, Clemson University, Clemson, South Carolina, USA Received 26 F e b r u a r y 1968

High purity polycrystalline magnesium s a m p l e s n e a r 4.2°K have been i r r a d i a t e d with 0.4 and 0.3 MeV e l e c t r o n s . Subsequent isochronal r e c o v e r y was observed to occur in two stages: one c e n t e r e d near 6.8°K and the other c e n t e r e d n e a r 11.4°K.

T h e low t e m p e r a t u r e r e c o v e r y s p e c t r u m h a s been obtained for pure magnesium after fast n e u t r o n i r r a d i a t i o n s [1]. W e h a v e r e c e n t l y d e termined the annealing behavior for polycrystalline magnesium samples after irradiating with e l e c t r o n s of 0.3 a n d 0 . 4 M e V . T h e s e b o m b a r d ments with mildly relativistic electrons create Frenkel defects in the bulk material which are s t u d i e d t o l e a r n a b o u t t h e d e f e c t s t a t e of s o l i d s

0

"•

'

'

" 0 . 4 0 MeV, &P.. 9.08

X

Io-IO,t'l' crn

AO.30 MeV, ~,po- 8.36 x Io'lO,[l'cm

20

~ 40

[2]. T h i n f o i l s a m p l e s w e r e p r e p a r e d by r o l l i n g l a r g e g r a i n s of m a g n e s i u m m a t e r i a l (99.999% nominal purity) that was obtained in lump form from Materials Research Corporation. Physical d i m e n s i o n s of a s a m p l e w a s 0 . 0 2 i n c h e s i n w i d t h , 0.001 i n c h e s i n t h i c k n e s s a n d 1.4 i n c h e s i n l e n g t h . Two separate samples were simultaneously s t u d i e d . T h e r a t i o of t h e r e s i s t i v i t y a t r o o m t e m p e r a t u r e t o t h a t a t 4 . 2 ° K w a s 610 f o r o n e s a m p l e a n d 310 f o r t h e o t h e r . S u c h a d i f f e r e n c e f o r t h e v a l u e s of t h e r e s i s t i v i t y r a t i o d o e s n o t a f f e c t t h e * This work was supported by the U. S. Atomic Energy Commission.

o ~ 80

so

=oo

I

i

i

i

I

I

15 TEMPERATURE

(°K}

Fig. 1. Isochronal r e c o v e r y of e l e c t r i c a l r e s i s t i v i t y for high purity m a g n e s i u m following i r r a d i a t i o n at 4.2°K with e l e c t r o n s of 0.3 MeV and 0.4 MeV incident energy.

453