Co_2FeSi Heusler Alloy Prepared by Arc Melting and Planar Flow Casting Methods: Microstructure and Magnetism

This paper is devoted to studies of the structural and magnetic properties of Co_2FeSi Heusler alloy produced by arc melting resulting in samples with large grains compared to finer-grained ribbon type samples prepared by planar flow casting. The scanning electron microscopy completed by energy dispersive X-ray spectroscopy, X-ray diffraction, and magnetic methods sensitive to both bulk and surface were applied. The chemical composition inside the grains was found to be in agreement with the nominal one while at the grain boundaries enrichment on Co and Si at expense of Fe was observed. The magnetic parameters derived from the bulk hysteresis curves resulted in nearly the same values of coercivity, about 1 kA/m, for both technological procedures while magnetization was of about 15 A m²/kg higher at ribbons compared with sample prepared by arc melting, 145 A m²/kg. The surface magnetic characteristics were visibly influenced by a surface magnetic anisotropy. The smooth polished surface of the sample prepared by arc melting has allowed visualizing the magnetic domain structure inside the grains and at grain boundaries by the magneto-optical Kerr microscopy and magnetic force microscopy