Disorder and weak localization effects in Co2MnxTi1−xAl Heusler alloy thin films

Abstract

The effects of disorder on the structural, magnetic and transport properties of stoichiometric Co2MnxTi1−xAl (0 ⩽ x ⩽ 1) thin films are reported. All the compositions exhibited B2-type structure with the actual composition of each film, as determined by Rutherford backscattering spectroscopy (RBS), being close to the nominal value. The values of saturation magnetization increase with increasing Mn content in the films and are in general agreement with the values obtained using the Slater–Pauling rule and the actual (RBS determined) compositions. Electrical resistivity as a function of temperature shows a change from metallic-type behaviour for x ⩽ 0.25 to a semiconducting type for x > 0.25. At lower temperatures (T < 25 K) metallic compositions show the presence of a resistivity minimum. The resistivity behaviour above low T upturn in metallic compositions follows a T2 dependence that is explained in terms of electron–electron scattering and one-magnon scattering. The presence of a resistivity minimum and the crossover from metallic to semiconducting type resistivity are explained in terms of localization effects originating mainly in the Co antisite disorder in these alloy films.