Properties of Co2YZ Heusler compounds

Heusler compounds of Co₂XY composition (Co₂Cr_0.6Fe_0.4Al, Co₂FeSi) offer a variety of half-metallic ferromagnetic materials. These were prepared by arc melting and comprehensively characterized by means of X-ray diffraction ( XRD), Mossbauer spectroscopy, magnetic X-ray circular dichroism spectroscopy (MXCD), superconducting quantum interference device (SQUID) magnetometry, electron spectroscopy for chemical analysis (ESCA), extended X-ray absorption fine structure (EXAFS) and Auger electron spectroscopy (AES) depth profiling. Structural disorder phenomena, magnetic hysteresis, magnetic moments, magnetic transition temperatures and Curie temperature were obtained. Band structure calculations were presented for ordered and disordered compounds. The connection between specific site disorder and the band structure was shown explicitly with particular emphasis on the half-metallic properties. Experimentally observed deviations from the ideal Heusler structure and from the simple Slater-Pauling rule for the magnetization were discussed in close relation to theoretical models.