Magnetic properties, structural characterization and magnetic damping constant of Co₂Fe_xMn_1−xSi Heusler alloys

Abstract

Co2FexMn1-xSi (0 <= x <= 1) Heusler alloys were fabricated by arc-melting the stoichiometric quantities of the constituents. We investigated the magnetic properties, geometric structure simulation, and real crystal structure for powder samples and the magnetic damping constant for polished thin-disk samples. All samples show high Curie temperatures, and the molecular magnetic moment increases with Fe concentration. The theoretical atomic site occupation of Co2FexMn1-xSi Heusler alloys with A2, B2, and L2(1) structures were simulated by Diamond 3.2. The real crystal structure was studied via x-ray diffraction measurement, followed by both Rietveld refinement and Fe-57 Mossbauer spectroscopy. The result indicates that in addition to the main phase of L2(1), some B2 phases coexist in the samples, which will decrease the gap at the Fermi level and destroy half metallicity. The corresponding magnetic damping constant, deduced from the ferromagnetic resonance, decreases as the concentration of the L2(1) phase increases. Therefore, the ordered L2(1) structure is the key factor for improving the half metallicity and decreasing the magnetic damping constant. The results suggest that the Co2Fe0.7Mn0.3Si Heusler alloy with a 100% L2(1) phase is more suitable for applications.