Ab initio study of magnetic properties of Fe-Mn-Al Heusler alloys
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Ab initio study of magnetic properties of Fe-Mn-Al Heusler alloys Vladimir V. Sokolovskiy1,2, Vasiliy D. Buchelnikov1, Mikhail A. Zagrebin1, Sergey V. Taskaev1, Vladimir V. Khovaylo2 and Peter Entel3 1
Chelyabinsk State University, Chelyabinsk, 454001, Russia
2
National University of Science and technology "MIS&S", Moscow, 119049, Russia
3
University of Duisburg-Essen, Duisburg, D-47048, Germany
ABSTRACT Density functional theory (DFT) based on the spin-polarized relativistic Korringa-KohnRostoker (SPR-KKR) method is used to investigate the magnetic properties of nonstoichiometric Fe2+xMn1-xAl Heusler alloys, where 0 ≤ x ≤ 0.9. The composition dependences of the magnetic exchange couplings and the Curie temperature for the cubic L21 phase are obtained. Our simulations have shown that the Fe-Fe nearest neighbors present a strong ferromagnetic coupling. Moreover, these exchange interactions are larger than other interactions. The substitution of Mn by Fe in Fe2+xMn1-xAl (0 ≤ x ≤ 0.9) leads to an increase in the Curie temperature. This tendency and the values of Curie temperatures are in agreement with the experimental results for Fe2+xMn1-xAl (x = 0, and 0.1). The highest Curie temperature was observed for the Fe-richer alloy. INTRODUCTION The Fe2+xMn1-xAl Heusler alloys have been intensively investigated in the last past years, and have attracted much attention from both experimentalists and theoreticians [1-8]. These alloys are interesting magnetic materials considering its promising technological applications in view of their properties such as anomalous behaviors of optical, magnetic and transport properties. The interesting properties are coupled to the competing ferromagnetic (FM) – antiferromagnetic (AF) exchange interactions between Fe atoms at the order-disorder structural transition from A2 to B2 structure [2, 3]. The effect of variations of composition around stoichiometric on the structural and magnetic properties of Fe2+xMn1-xAl (x = 0, and ± 0.1) has been studied experimentally by Paduani et al. [4]. As it has been shown, the Curie temperature and saturation magnetization increased with the Fe content. Recently, Omori et al. investigated the addition of Ni to Fe-Mn-Al alloys in order to improve their magnetic and structural properties. For one composition, Fe43.5Mn34Al15Ni7.5, the superelastic behavior was observed over a temperature range from 77 to 513 K [5]. It offers great promise as a candidate for largescale applications such as space, automobile, and seismic technologies. From theoretical point of view, the magnetic, structural and electronic properties of FeMn-Al compounds have been studied recently by means of first-principles calculations [6-8]. The role of the orbital magnetism in the half-metallic and full-metallic Heusler alloys by means of fully relativistic screened KKR method is studied by Galanakis [6]. As it has been shown, the orbital moments are almost completely quenched and they are negligible with respect to the spin moments. Results of the investigations of the optical prope
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