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Abstract:
The classical concept of band structure tuning as used for semiconductors by partly replacing one atom by a chemical neighbor without altering the structure is applied examplarily to the half-metallic ferromagnetic Heusler compound Co2Cr1-xFexAl. Band structure calculations are presented for ordered and disordered compounds. We present experimental and theoretical results. The connection between specific site disorder and the band structure is 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 are discussed in close relation to theoretical models. It has been found that the orbital magnetic moment and hence the spin-orbit coupling is important for the understanding of the half-metallicity. Experimental techniques which can be used to determine the electronic properties are described.