Influence of preparation technology on microstructural and magnetic properties of Fe2MnSi and Fe2MnAl Heusler alloys

Abstract

Microstructural and magnetic properties of the X(2)YZ, namely Fe2MnSi and Fe2MnAl, Heusler alloys have been studied from the viewpoint of technology for their production and for the Z element effect. First, arc melting was applied to produce button-type ingots from which samples in a form of 500 mu m thick discs were cut. Second, planar flow casting technology yielded samples in a ribbon-form 2 mm wide and 20 m thick. The checked area chemical compositions were in agreement with the nominal ones. Nevertheless, the darker square objects and smaller bright objects observed at the wheel side of the Fe2MnSi ribbon sample yielded higher Mn content at the expense of Fe. The X-ray diffraction patterns of all samples have indicated L2(1) structure with lattice parameters, 0.567 (1) nm for Fe2MnSi and 0.584 (1) nm for Fe2MnAl, being within an experimental error independent of production technology. On the other hand, the technology has markedly influenced the microstructure clearly pointing to the larger size of grains and grain boundaries in the disc samples. From the magnetic viewpoint, both alloys are paramagnetic at room temperature without visible influence of their production. On the contrary, the low-temperature behavior of the microscopic hyperfine parameters and the macroscopic magnetic parameters exhibits differences affected by both chemical composition and microstructure.