Electronic structure, optical, and magneto-optical properties of Co2CrGa Heusler alloy films: Experimental and theoretical study

Abstract

The optical and magneto-optical properties of bulk L21 ordered Co2CrGa Heusler alloy (HA) have been experimentally investigated for the first time below and above the Curie temperature (T≈1.2TC) and explained in terms of the band structure. It is shown that the optical properties of Co2CrGa in paramagnetic phase look similar to those in the ferromagnetic phase. Crystallization of amorphous Co2CrGa HA films with the formation of B2-type of order causes significant increase in alloy resistivity due to formation of the energy gap at the Fermi level in the minority bands. Unlike bulk L21-type ordered Co2CrGa HA sample B2 structural order of Co2CrGa HA films exhibit negative temperature coefficient of resistivity for 80–750 K temperature range. Atomic disorder causes redshift in the interband absorption peak by about 0.6 eV (and hence corresponding reduction in the energy distance between initial and final energy bands responsible for this peak formation).