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SHORT-RANGE ODER IN TRANSITION METAL-METALLOID GLASSES
I. Vincze, F. van der Woude, J. Balogh
To cite this version:
I. Vincze, F. van der Woude, J. Balogh. SHORT-RANGE ODER IN TRANSITION METAL- METALLOID GLASSES. Journal de Physique Colloques, 1980, 41 (C1), pp.C1-257-C1-258.
�10.1051/jphyscol:1980187�. �jpa-00219780�
JOURNAL DE PHYSIQUE Colloque C1, suppl6ment au n o 1 , Tome 41, janvier 1980, page C1-257
SHORT-RANGE ORDER IN TRANSITION METAL-METALLOID GLASSES
I. Vincze, F. van der Woude and 4- J. ~ a l o g h '
Solid S t a t e Physics Laboratory, Mat6riaZs Science Center, University of Groningen, Groningen, The Netherlands.
*
Central Research I n s t i t u t e for Physics, Budapest, hrungq.A typical metallic glass consists of transi- tion metal with about 15-25 at.% of one or more kinds of metalloids. Their structure and especial- ly the nature of the short-range atomic arrange- ments is a problematic issue arising from difficul- ties in getting direct experimental information.
The most direct information on the atomic structure of metallic glasses has been obtained from conven- tional X-ray and neutron scattering measurements in terms of the interference function. Although the interference functions contain information on both the short-range order and long-range order in these amorphous alloys, this information can only be ex- tracted by complex procedures which involves theo- retical models. However, even if all the individual partial structure factors are determined separately, only the average of the atomic configurations can be obtained
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no detailed information on the proba- bility distributions of different possible atomic configurations is available.The hyperf ine field distribution p (H) determi- ned by Mtjssbauer spectroscopy gives valuable infor- mation in the study of short-range order because of
its sensitivity to local environments. The evalua- tion of p(H) from the strongly broadened and over- lapping lines of the l~l~ssbauer spectra is a diffi- cult task. The unknown intensities of the second and fifth lines may cause serious systematical er- rors in the determined p(H) ; especially the presen- ce of paramagnetic components can be misinterpreted as a "tail" in p(H) (i.e. the distribution spreads to zero field) as it has been done for Fe75P15C10 /I/ and Fe32Ni36Cr14P12B6 (MG 2826A) /2/. The SyS- tamtical errors related to the overlap of the li- nes can be avoided with the simple procedure des- cribed in Ref. 3. In some cases (e. g. FegoB20) the
p(H) distributions determined by different methods agree reasonably well with each other /3,4,5/.
These distributions are often structureless and can be approximated by a Gaussian form, i.e. it can be characterized with two parameters: with the average hyperfine field and with the width of the distribu- tion.
The interpretations of the measured p(H) are widely different. Recently, the p(H) of amorphous FegoBz0 y s successfully explained /4/ in the model of dense random packing of hard spheres (DRPHS). In this interpretation the p(H) distribution is attri- buted to the fluctuating number of iron neighbours resulting in a contribution of AH % 24.5 W e by each close-contact iron atoms to the hyperfine field at a given iron site and the close-contact coordination probabilities were taken from the Ber- nal liquid-structure model / 6/. Similar intemreta- tion of p(H) was given for other metallic glasses, as well / 7 / .
However, serious objection can be raised against such aninterpretation of the p(H) distri- bution: there is no evidence for the supposed strong neighbour contribution to the hyperfine field. Contrary, in metallic glasses as in crystal- line intermetallic compounds the iron hyperfine field is proportional to the iron magnetic moment /8/ which is determined mostly by the metalloid neighbourhood. For example, in crystalline Fe3B and FeB tie iron atoms with 3 B and 10 Fe; 4 B and 10 Fe; 6 B and 10 Fe nearest neighbours have a hyper- fine field of 275 m e , 235 kOe and 130 m e , respec- tively /9/. That is, these iron atoms have nearly the same iron neighbourhood, while their boron en- vironment varies widely and correlated with the va- riation observed in hyperfine field. Similarly, the +On leave from the Central Research Institute for
Physics, Budapest, Hungary.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1980187
c1-258 JOURNAL DE PHYSIQUE
substitution of half of the Fe by Ni (with much
smaller magnetic moment) in amorphous Fe40Ni40B20 does not influence the shape of p(H) and the average hyperfine field is decreased only by about 15% sug- gesting a rather localized type of behaviour /lo/.
Mijssbauer data of amorphous Fe obtained by co-con- densation of 10 at.% Ar are in accord with the above argument /11/: the linewidth of this spectrum is 5 0.4 - mm contrary to that of amorphous FegOBZO which
sec mm
is O 1.5 /3/. Since the evaporated Fe with the non-interacting Ar impurities is the nearest to the assumptions of the DRPHS model, the remarkable dif- ference between the linewidths (i.e. in the widths of the p(H) 's) suggests the dominant role of the me- talloid neighbours in determining the p(H) distribu- tion.
In the absence of fixed coordination number the distribution of the metalloid atoms is quite diffe- rent from that of the transition metal atoms (the metalloid atoms are sitting in the holes of the
transition metal framework according to the DRPHS model). As a result p(H) based on the metalloid dis- tribution of a DRP models differs considerably from the measured one /9/.
On the other hand, it has been shown that the short-range order of amorphous Fe75B25 can be well approximated with that of the metastable crystalline Fe3B compound / 1 2/.
This work forms part of the research program of the Foundation for Fundamental Research on Matter
(FCPUI) and was made possible by financial support from the Netherlands Organization for the Advance- ment 05 Pure Research (ZWO).
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