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MÖSSBAUER STUDY OF AMORPHOUS Fe-B, (Fe,Ni) SiB, (Fe,Ni) PB ALLOYS
Jessica Dubois, Gérard Le Caër, A. Amanou, U. Herold
To cite this version:
Jessica Dubois, Gérard Le Caër, A. Amanou, U. Herold. MÖSSBAUER STUDY OF AMORPHOUS
Fe-B, (Fe,Ni) SiB, (Fe,Ni) PB ALLOYS. Journal de Physique Colloques, 1980, 41 (C1), pp.C1-247-
C1-248. �10.1051/jphyscol:1980182�. �jpa-00219775�
JOURNAL DE PHYSIQUE
CoNoque
Cl, supplkment
aun
O 1,Tome
41,janvier
1980,page
Cl-247~ S S B A U E R STUDY OF AMORPHOUS Fe-B, ( F e t ~ i . 1 SiB, ( F e t ~ i )
PB
AUOYS J . M . Dubois, G. Le Caer, A. Amamou and+
U. IieroldXLaboratoire de Me'taZZurgie no 159, EcoZe des Mines, 54042
-
NANCY-DEDEX, f i n c e .+
Laboratoire de Structure EZectronique des SoZides, 4, rue BZaise Pascal, 67000 STRASBOURG, France.x InstitLct f U r Werkstoffe, Ruhr-Universitdt Bochum, 0-4630 BOCHUM, F. R. Germany.
As c l e a r l y shown by Balogh and Vincze / I / , t h e width of t h e h y p e r f i n e f i e l d d i s t r i b u t i o n a t a g i v e n temperature, i n FegoB20, cannot be a s c r i b e d t o exchange f l u c t u a t i o n s /2/. It must t h e n be mainly r e l a t e d t o compositional d i s o r d e r and t h e h y p e r f i n e f i e l d d i s t r i b u t i o n s may g i v e u s e f u l i n - formations about t h e chemical o r d e r i n t h e s e amor- phous a l l o y s .
The assumption of a random d i s t r i b u t i o n of t h e h y p e r f i n e f i e l d d i r e c t i o n s w i t h r e s p e c t t o t h e p r i n c i p a l axes of t h e EFG t e n s o r l e a d s t o a peak shape sT)(b)/3/ which depends on t h e asymmetry para- meter
n
and on t h e quadrupole s p l i t t i n g A. The mean quadrupole s p l i t t i n g sh
have been measured i n melt- spinned FelOO-xBx amorphous a l l o y s , a s a f u n c t i o n of x (14 2 x S 25), i n t h e paramagnetic s t a t e b e f o r e c r y s t a l l i s a t i o n t a k e s p l a c e .-
A ranges from 0.4 t o 0.5 mm/s while t h e a c t u a l v a l u e s a t room temperature may b e s l i g h t l y g r e a t e r ( l a s t s e c t i o n ) .1
-
Hyperfine f i e l d s d i s t r i b u t i o n s i n Fe B 100-x x amorphous a l l o y sThe published h y p e r f i n e f i e l d d i s t r i b u t i o n s i n such amorphous a l l o y s a r e g e n e r a l l y s t r u c t u r e - l e s s , due t o t h e assumption A = 0 and i n some c a s e s to a l a c k of r e s o l u t i o n of t h e s p e c t r a . A s t r u c t u r e i s i n f a c t observed when the broade- ning of t h e peaks i s taken i n t o account /3,4/.
The room temperature H6ssbauer s p e c t r a of Fe,OO-xBx amorphous a l l o y s a r e f i t t e d u s i n g a c o n s t r a i n e d H e s s e - ~ i i b a r t s c h method 131 and t h e S 1
(3
peak shape (1.35 5 X 2 S 2.22). The hyper- f i n e f i e l d d i s t r i b u t i o n s ( f i g u r e 1) i n c l u d e f o u r o r f i v e apparent peaks according t o t h e composi- t i o n . The i r o n and boron c o o r d i n a t i o n s c h a r a c t e - r i z i n g each peak a r e deduced from a comparison of t h e observed h y p e r f i n e f i e l d s t o t h o s e foundFIGURE 1 : Hyperfine f i e l d d i s t r i b u t i o n s i n FelOO-xBx a t room t e g e r a t u r e
( h = (H = H)/6 where a is the
mean magnetization p e r Fe atom a t R.T.) i n c r y s t a l l i n e b o r i d e s i n which t h e boron atoms a r e a t t h e c e n t e r of t r i g o n a l prisms capped with t h r e e ,half-octahedra. I n t h e s e b o r i d e s , t h e t o t a l c o o r d i n a t i o n of i r o n atoms i s such t h a t
12 I;
%e
+ nB I; 14 while t h e i r o n hyperfine f i e l d s a t e mainly determined byng
and d e c r e a s e whenng
i n c r e a s e s w i t h a s l o p e AH/Ang -
=
30 kOe. The above d e s c r i b e d polyhedron is t h e b a s i s of t h e s t r u c t u r a l model of Gaskell / 5 / w h i l e t h e e x i s t e n c e of a mole- c u l a r u n i t with a f i x e d s t r u c t y k e i s a l s o emphasi- zed by Boudreaux / 6 / . Figure 1 shows t h a t t h e in- t e n s i t i e s of t h e two low f i e l d peaks a s s o c i a t e dArticle published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1980182
Cl-248 JOURNAL DE PHYSIQUE
w i t h i r o n atoms h a v i n g (4-5) boron n e i g h b o u r s de- c r e a s e ( f i g u r e 2) w h i l e t h o s e c o r r e s p o n d i n g t o i r o n atoms w i t h (2-3) boron h e i g h b o u r s o n l y s l i g h t l y d e c r e a s e when x d e c r e a s e s from 25 t o % 17. The f r a c - t i o n of i r o n atoms w i t h (0-1) boron n e i g h b o u r s i n - c r e a s e s from % I 5 t o 35 % i n t h i s c o n c e n t r a t i o n r a n g e . The mean i r o n c o o r d i n a t i o n o f i r o n h a s a l r e a - dy been detenrtined 171. The mean boron c o o r d i n a t i o n
-
nB, deduced from f i g u r e I , ( f i g u r e 2) i n c l u d e s t h e u n c e r t a i n t i e s i n t h e nB d e t e r m i n a t i o n . The c u r v e may b e s h i f t e d upwards o r d o m w a r d s by % 0 . 2 . nB-
i s much h i g h e r t h a n p r e d i c t e d by Boudreaux's model 181 b u t i s c l o s e t o t h e
%
p r e d i c t e d by t h e q u a s i - c r y s t a l l i n e model of Vincze e t a 1 . / 8 / a l - though t h e p r o b a b i l i t i e s o f f i g u r e 2 d i f f e r from t h o s e g i v e n by t h i s model. T h i s o n l y means t h a t t h e a l r e a d y quoted polyhedron ( Z-
9) may c o n s t i t u t e t h e building u n i t o f t h e s e amorphous a l l o y s . The p r o b a b i l i t i e s f o r (0-1) B n e i g h b o u r s a r e lower t h a n p r e d i c t e d by t h e DRPHS model 1 8 1 a t l e a s t down t o Q, 16-17, i n agreement w i t h t h e proposed s t r o n g s h o r t - r a n g e o r d e r i n g i n e u t e c t i c l i q u i d s o f t r a n s i - t i o n m e t a l s w i t h B, C , P 191.FIGURE 2
F r a c t i o n of i r o n atoms w i t h (0-11, (2-3) ( 4 - 5 ) B n e i g h b o u r s and mean boron c o o r d i n a - t i o n o f i r o n atoms n
B'
2
-
Quadrupole s p l i t t i n g s i n (Fe Nil-y)79P13B8 Y(y = 0.1, 0.2, 0.3) and (FelONigo) Si2B19
independent below % 300 K w h i l e t h e y d e c r e a s e s l i g h t l y above = 300 K w i t h a mean s l o p e o f t h e o r d e r of 1 x 10 -4 m m / s / " ~ . I n (Fe Ni,,y)79P13B8,
-
YA (= 0 , 6 0 m/s a t 296 K) i s independent o f y w h i l e
B
= 0.55 m / s a t 296 K i n (FelONigo) S i 2 B l g .REFERENCES
BALOGH J . and VINCZE I., ~ o l ' i d S t a t e Corn,
5
(1978) 695.
TSUEI C .C. and LILIENTHAL H., Phys
.
Rev. B,13
(1976) 4899.
LE CAER G . and DUBOIS J.M., J. Phys. E : S c i . I n s t r u m . (1979) t o b e p u b l i s h e d .
GONSER U., GHAFARI M. and WAGNER H.G., J . Mag.
Mat.
8
(1978) 175.GASKELL P.H., J. Non Cryst: S o l
2
(1979) 207.BOUDREAUX D.S., Phys. Rev. B
fi
(1978) 4039.FUKUNAGA T
. ,
MISAWA M., FUKAMICHI K. ,
MASUMOTO T. and SUZUKI K., Rapidly Quenched M e t a l s 111, (Ed. B. Cantor)
2
(1978) 325.VINCZE I., BOUDREAUX D.S. and TEGZE M., PhyS.
Rev. B (1979) t o b e p u b l i s h e d .
GILMAN J.J., P h i l . Mag. B
37
(1978) 577.1101 CHIEN C.L., Hyp. I n t e r . (1978) 869.
I n t h e paramagnetic s t a t e , s l i g h t l y asymme- t r i c d o u b l e t s a r e observed showing, i n agreement w i t h C h i e n / l o / , t h a t b o t h A and t h e isomer s h i f t a r e d i s t r i b u t e d . I n a l l t h e i n v e s t i g a t e d samples, t h e mean q u a d r u p o l e s p l i t t i n g s
