The distinctness of magnetic hyperfine fields associated with structurally unique iron sites in Fe 3 B
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WOONG K. CHOO is with Korea Advanced Institute of Science, Chongyangni, Seoul, Korea, and ROY KAPLOWis with Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139. Manuscript submitted September 29, 1976. METALLURGICAL TRANSACTIONS A
MAGNETIC H Y P E R F I N E F I E L D The c r y s t a l s t r u c t u r e of FeaC is o r t h o r h o m b i c and i t s s p a c e group is P b m n . T h e r e a r e two t y p e s of i r o n - a t o m l a t t i c e s i t e s , T y p e I and T y p e II, p r e s e n t in the r a t i o 2 : 1, r e s p e c t i v e l y . 1 The c r y s t a l s t r u c t u r e of Fe3B i s i s o s t r u c t u r a l to that of Fe3C. 6'7 The M S s s b a u e r d a t a is shown in F i g . 1; t h r e e s e p a r a t e c o n t r i b u t i o n s a r e e v i d e n c e d , e a c h one a s i x - p e a k , f e r r o m a g n e t i c s p e c t r u m . The s o l i d c u r v e is not a t h e o r e t i c a l fit, but i s ( c o m p u t e r ) d r a w n t h r o u g h the d a t a points to a i d r e a d a b i l i t y . T h e p r o m i n e n t s i x - p e a k s p e c t r u m i s that of a - i r o n (Fep in F i g . 1). The l e s s i n t e n s e s p e c t r a of two t y p e s of a t o m s (Fei and F e i i ) in FeaB a r e c h a r a c t e r i z e d by m a g n e t i c h y p e r f i n e f i e l d s of 235 + 5 KOe and 264 • 5 KOe, r e s p e c t i v e l y ; a p p r o x i m a t e i s o m e r and q u a d r o p l e p a r a m e t e r s a r e given in T a b l e I. The r e l a t i v e i n t e n s i t y of the l a t t e r two s p e c t r a is 2 : 1, within the s t a t i s t i c a l p r e c i s i o n of the d a t a , a s a n t i c i p a t e d f r o m the r e l a t i v e n u m b e r of e a c h of the two t y p e s of i r o n - a t o m s i t e s in Fe3B. The o r t h o r h o m b i c c r y s t a l s t r u c t u r e of c e m e n t i t e (Fe3C) was e s t a b l i s h e d by L i p s o n and P e r c h . x Subs e q u e n t X - r a y d i f f r a c t i o n and n e u t r o n s c a t t e r i n g s t u d i e s on c e m e n t i t e have not changed the b a s i c s t r u c t u r e which t h e y p r o p o s e d ( b a s e d on a b u i l d i n g b l o c k in the s h a p e of a t r i a n g u l a r p r i s m ) but p a r a m e t e r s v a r y f r o m i n v e s t i g a t i o n to i n v e s t i g a t i o n , v's A d e t a i l e d X - r a y d i f f r a c t i o n s t u d y by F a s i s k a and J e f f r e y , u s i n g a F o u r i e r a n a l y s i s method, s e e m s to have 9 y i e l d e d l a t t i c e p a r a m e t e r s of i n c r e a s e d a c c u r a c y . T h e s e and o t h e r l a t t i c e p a r a m e t e r s a r e given m T a b l e I.lO '
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Fig. 1--Mossbauer spectra of FeaB. Fep denotes the pure iron spectrum. Fe I and FeII denote Type I and Type II iron spectra in Fe3B. VOLUME 8A, MARCH 1977-417
Table I. M6ssbauer Data on Iron-Bo
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