Electronic structure, magnetic, transport, and optical properties of bulk and film Fe2CrGa Heusler alloy. Effect of structural disorder

摘要

Magnetic, transport, and optical properties of thin film and bulk Fe2CrGa alloy samples with different types of atomic order were experimentally investigated. The obtained data were discussed in terms of first-principle calculation results made for the stoichiometric Fe2CrGa alloy with different types of atomic order and disorder. An ultimate atomic disorder in Fe2CrGa alloy films was obtained by employing vapor quenching deposition onto substrates cooled by liquid nitrogen. Annealing of as-quenched Fe2CrGa alloy films causes their crystallization at Tann=750 K with the formation of the disordered A2-type structure, which is accompanied by the rapid growth of alloy resistivity in a narrow temperature range, formation of multi-phase magnetic structure and changes in the optical properties. Crystalline bulk and film Fe2CrGa alloy samples show the dome-like temperature dependence of the resistivity with maximums near their Curie temperatures and explained in terms of competition between negative with temperature contribution from highly resistive media and positive from the electron–magnon scattering. The big resemblance between calculated for Hg2CuTi type of atomic order and experimental optical conductivity spectra for annealed Fe2CrGa alloy films proves that Hg2CuTi type of atomic order is more probable for this alloy.