Determination of Long-Range-Order Parameter of Fe<SUB>3</SUB>Si Alloy by means of <SUP>57</SUP>Fe M&ouml;ssbauer Effect

Abstract

A site population analysis of iron atoms in Fe3Si alloys with D03 superlattice structure was performed by 57Fe Mossbauer spectroscopy using crushed and annealed powder specimens with silicon concentrations of 23.3 and 25.5 at%. The Mossbauer spectra obtained were found to be superpositions of at least three six-line components. The relative intensity for each component has been analyzed using the thin foil approximation. The atomic configuration and the relative number of iron atoms of the component were determined from the values of the hyperfine field and the relative intensity for each component, and from these data the short-range-order parameter was determined.In order to determine the long-range-order parameters of the alloys, a two step procedure was used: First, the perfectly ordered D03 lattice of 25 at% Si was constructed by computer, and then atoms were replaced randomly so that any desired values of the alloy concentration and the degree of order are reached. By comparing the computer simulation with the result of the Mossbauer experiment, the long-rangeorder parameters, S(D03) and S(B2), were determined. The values agree well with those obtained by the powder X-ray diffraction technique. (Received June 12, 1985) Keywords: Mossbauer spectroscopy, site population, atomic configuration, hyperfine field order-disorder transformation, iron-silicon alloys, DO3 lattice, B2 lattice, long-range-order Parameter. short-range-order parameterAs shown in the equilibrium phase diagram, the Fe-Si alloy near room temperature has a disordered structure (bcc) when the silicon concentration is less than 10 at%, the B2 structure for 10-20 at% Si and the D03 structure for 12-25 at% Si. Especially in the composition region of 12-24 at% Si, the temperature change induces a phase transformation among D03, B2 and bccc(1).57Fe Mossbauer spectra of ferromagnetic materials show the nuclear Zeeman splitting which is caused by the hyperfine field at the nucleus. In many ferromagnetic iron alloys, the electronic state of 57Fe and the hyperfine field at 57Fe nucleus mainly depend on the surrounding atomic configuration; this is the so called local environment effect. Fe3Si and Fe3Al are typical examples of compounds which show a large local environment effect. Many 57Fe Mossbauer spectroscopic studies (besides a great number of results obtained by other methods) have been reported on these alloy systems to investigate the site populations in ordered and disordered states of these alloy systems(2)- (15) .Information which can be obtained directly from Mossbauer spectra in this alloy system depends mainly on the short-range atomic configurations. However, if it is possible to determine long-range-order parameters by Mossbauer spectra, this method is very useful to gain information on order-disorder transformations which is usually obtained from other methods such as X-ray diffraction, because data on short-range and on long-range order can be obtained at the same time. In this method, neither single crystals nor very fine powders ...

Induced magnetism on silicon in Fe3Si quasi-Heusler compound

“…Conversion electron Mössbauer spectroscopy (CEMS) at perpendicular incidence of the γ-rays onto the film surface was employed to investigate the degree of D0 3 order of the two samples. The experimental CEMS data can be fitted by the procedure described by Arita et al 6 , yielding the long-range ordering parameters S(D0 3 ) and S(B2). The samples prepared here obviously display a high degree of chemical and structural order as can be seen from the Mössbauer results shown in Fig.…”

“…Due to the different neighborhood in the D0 3 structure, Fe-A and Fe-B atoms have different magnetic moments, namely 1.2 µ B and 2.4 µ B as obtained from neutron diffraction experiments 5 . The structure of Fe 3 Si can be represented by the long-range ordering parameters S(B2) and S(D0 3 ) which are defined by the occupation probabilities P i of Fe at the different lattice sites i =A, B by the following equations 6 .…”

Effect of chemical order on the magnetic and electronic properties of epitaxial off-stoichiometryFexSi1−xthin films

“…The sample is primarily chemically disordered on the Fe I site, thus is B2 structure. 35,36,37 Figures 4a,b show M(T) with H=1000 Oe for x=0.65, 0.55 and M(H) for x=0.75 (2K), 0.65 (300K) and an amorphous sample with x=0.65 (300K) from our previous work. 33 Comparison of the hysteresis loops shows that the epitaxial x=0.65 sample is ferromagnetic at 300K, where the CEMS analysis is made and saturates magnetically at approximately 800 Oe.…”

Improved interfacial local structural ordering of epitaxial Fe3Si(001) thin films on GaAs(001) by a MgO(001) tunneling barrier

“…Financially supported by DFG (SFB 491). 1 and a 2 ) and long-range order parameters S(B2) and S(D0 3 ) for samples B and C obtained from measured CEM spectra and Fe 3 Si lattice simulations using the method by Arita et al 17 x R (Si), x(Si): calculated Si concentrations (at. %), following Refs.…”

“…nn ¼ 8 Si atoms) and tetrahedral (max. nnn ¼ 6 Si atoms) symmetries of the Fe 3 Si unit cell.TABLE I. Probability (in %) for nn Si and nnn Si neighboring configurations around 57 Fe atoms for sample B obtained by simulation following Arita et al17 Probabilities 0.1% were set to zero, including all configurations of nn ¼ 0 and 1. For sample B (sample C), r A ¼ 0.not observed, and the low line intensities can be explained by substitution of Fe by Si atoms.…”