57Fe AND 61Ni MÖSSBAUER EFFECT INVESTIGATIONS OF NICKEL FERRITE-ALUMINATES

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57Fe AND 61Ni MÖSSBAUER EFFECT INVESTIGATIONS OF NICKEL

FERRITE-ALUMINATES

J. Bara, Z. Stadnik, G. Czjzek, J. Fink, V. Oestreich, H. Schmidt

To cite this version:

J. Bara, Z. Stadnik, G. Czjzek, J. Fink, V. Oestreich, et al.. 57Fe AND 61Ni MÖSSBAUER EFFECT INVESTIGATIONS OF NICKEL FERRITE-ALUMINATES. Journal de Physique Colloques, 1980, 41 (C1), pp.C1-173-C1-174. �10.1051/jphyscol:1980148�. �jpa-00219717�

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JOURNAL DE PHYSIQUE Colloque C1, supplt!ment au no 1 , Tome 41, janvier 1980, page C1-173

57 ' 61

Fe AND Ni M~~SSBAUER EFFECT INVESTIGATIONS OF NICKEL FERRITE-ALUMINATES

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J.J. Bara, Z.M. Stadnik, G. Czjzek , J. Fink , V. Oestreich and H. Schmidt I n s t i t u t e of Physics, Jagielzonian University Reymonta 4 , 30-059 Cracow, PoZand Kernforschungszatrwn kartsruhe, I n s t i t u t fur Angewandte Kemphysik, 0-7500 KarZsruhe, Postfach 3640, F.R. G.

I n this gtaper we r e p o r t on some new re- s u l t s of 573?e a d 6117i i11Ussbauer e f f e c t i n v e s t i g r t ions o f ltiFep-91x04 n e r i e s [I]

.

Low t e n p e r a t u r e 571?e s p e c t r a of a l l inves- t l g a t e d samples a r e i n t e r p r e t e d a s con- posed of t e t r a h e d r a l (A) and o c t a h e d r a l

( 8 ) Zeenan p a t t e r n s . The i n f l u e n c e of t h e randoa d i s t r i b u t i o a o f id3+,

xi2+

^and

re3+

i o n s i n t h e A end 13 s i t e s on t h e hyperfine f i e l d s corresponding t o t h e s e s i t e s , xani- f e s t s i t s e l f i n t h e broadening of Zeernan components. A t e l e v a t e d temperatures re- l a x a t i o n p r o c e s s e s begin t o play an i m - p o r t a n t role. They appear a t lower tempe- r a t u r e s f o r h i g h l y d i l u t e d samples t h a n f o r weakly d i l u t e d ones. The shapes of re- l a x a t i o n s a e c t r a i n d i c a t e t h a t t h e magnet- i c type of r e l a x a t i o n p r o c e s s , w i t h only a s n a l l c o n t r i b u t i o n of t h e super2aramagnet- i c p r o c e s s , i s involved. Sose s p e c t r a o f each of t h e i n v e s t i g a t e d samples ( ~ i ~ . 1) show r e l a x a t i o n f e a t u r e s o v e r temperature r e g i o n s below a 2 p r o p r i a t e C u r i e t a ~ p e r a - t u r e s Tcb These r e g i o n s a r e narrow f o r weakly d i l u t e d samples and r e l a t i v e l y 1-ge f o r h i g h l y d l l u t e d ones [Pig. 2 ) In r e g i o n A s t a t i c Z e a w p a t t e r n s are ob- served. R e l a x a t i o n s p e c t r a a r e found i n r e g i o n B, while i n region C quadrupole

d o u b l e t s a r e r e g i s t e r e d . For each o f t h e

FIG. 1.-Selected 5 7 ~ e s p e c t r a of t h e x=0.2 sample.

i n v e s t i g a t e d s a a p l e s a quadrupole doublet i s observed below t h e magnetometric C u r i e temperature. T h i s seems t o be cleclr evi- dence of t h e i n f l u e n c e o f t h e e x t e r n a l

magnetic f i e l d on t h e r e s u l t s derived Prom

-- magnetoaetric measure-

FIG. 2.-The diagram of t h e t y p e s of 57pe Mdssbauer s p e c t r a .

r e l a x a t i o n proceseee. Prom t h e s p e c t r a of r e g i o n A, t h e parameters c h a r a c t e r i z i n g t h e s u 2 e r t r a n s f e r r e d h y p e r f i n e f i e l d s , w h i l e from t h o s e o f region B, t h e relax- a t i o n times, a r e being s t u d i e d .

5 7 ~ e ~ p e c t r a f o r t h e ~ ~ 1 . 5 a m p l e were

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1980148

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c1-174 JOURNAL DE PHYSIQUE

tailen a t 4.2 K i n 0, 4, 10, 30 azcd 63 kGs for a a t i f e r r o m a g n e t s [2]

,

s i n c e t h e x=7.5 l o n g i t u d i n a l e x t e r n a l magnetic f i e l d s .

Some of them a r e shorm i n Fig. 3. The spec- trwn i n HeXt=O i s decorcpoaed i n t o t h r e e

. , , , , , , , components. From t h e l i n e w i d t h of t h e a o s t i n t e n s e one i t * i s cancxded t h a t both A and B Zeeman p a t t e r n s a r e contained i n i t . The weak component

V E L O C I T V Imnfu~I

FIG. 3.--57~e s p e c t r a a t 4.2 K of t h e x=1.5 s m p l e .

I1 with t h e l a r g e s t s p l i t t i - n g cones from t h o s e & - s i t e f e r r i c i o n s whose neareat- -neighbour c o o r d i n a t i o n s h e l l i s more r i c h i n Fe and X i etoms than on t h e average.

The non-resolved comgonent 111 comes from Fe i m p u r i t i e s i n t h e berylium s w g l e holder. The e x t e r n a l magnetic f i e l d s p l i t s coaponent I i n t o t w o - p a r t s , i n c r e a s e s t h e s p l i t t i n g of component I1 by a v a l u e di- r e c t l y corresponding t o HeXt and induces a Zeeman s g l i t t i n g of t h e non-magnetic component 111. From t h e behaviour of component I1 i n Hext i t i s concluded t h a t this component corresponds t o i r o n B s i t e s i n which Fe magnetic moments a r e c o l l i n -

e a r l y o r d e r e d end a l i g n e d a n t i p a r a l l e l t o t h e He,+ vector. The i n t e n s i t y of Am=O l i n e s of t h e coiaponent I at first dec?xass w i t h t h e i n c r e a s e i n HeXt a?d then in- c r e a s e s f o r s t i l l h i g h e r He,*. T h i s maybe explained by t h e i n f l u e n c e of

111 .

S i m i l a r phenomenon was observed e a r l i e r f o r unother spine1[3].

Hat=60 kGs f o r s m p l e s up t o x=1.25(~%3) m e i n t e r p r e t e d as being due t o 23. i o n s occupying only t h e l3 s i t e s , w i t h a nega- t i v e h g p e r f i n e Pield. 33r x=l. 5 and 1.9

s a x p l e s Xi. i o n s a r e

98 0

3 ⁹⁶⁰ found both i n the A

-

z 1m.o and B p o s i t i o n s .

- V)

gas

V) z From t h e s p e c t r e of

4

E P1.0

t h e x=1.3 s a m p l e i s

- Lo

^{i0 i0} ^Lo i t i s found t h a t

FIS. 4.-51i~i s p e c t r a a t 4.2 K of t h e x=1.25 sanple.

t h e signs of h y p e r f i n e f i e l d s a t t h e A and B s i t e s a r e both c e g a t i v e .

A more d e t a i l e d a n a l y s i s with t h e new r e s u l t s i n c l u d e d *Nil1 be published else- where.

Acknowledbments.-We wauld l i k e t o t h a r ~ k D r . W. Z a r e k f o r providing u s w i t h t h e sanples.

Ref erences

[I]

BARA J. J., P$DZIiVIATR A. T., STADITIK Z.

x.,

SZYTWA A.,

TODOF~OVICV

J., T&ECO'IVICZ Z . and ZAREK V., Phys.

S t a t . Sol. ( a ) 44 (1977) 325.

[2] F W X E L R. P., :~IPfssbauer E f f e c t Xethodology, Vol. 9 , p. 151,

(plenum p r e s s ) 1974.

(31 PIEKOSZEWSKI J., XOIJWICKI A., ~ A I S K I

J., KISY~SKA K., bXILACKA A. and XAKOLAC'JYA S., Proc. I n t . Conf. on idbssbauer S p e c t r . , a u c h a r e s t

,

^1377,

Vol. 1, p. 163.