Structural, magnetic, and transport properties of Co2CrAl epitaxial thin film

Abstract

We report the physical properties of Co2CrAl Heusler alloy epitaxial thin films grown on a single-crystalline MgO(001) substrate using a pulsed laser deposition technique. The x-ray diffraction pattern in the θ-2θ mode showed the film growth in a single phase B2-type ordered cubic structure with the presence of (002) and (004) peaks, and the film oriented along the MgO(001) direction. The ϕ scan along the (220) plane confirms the fourfold symmetry, and the epitaxial growth relation is found to be Co2CrAl(001)[100]||MgO(001)[110]. The thickness of about 12 nm is extracted through the analysis of x-ray reflectivity data. The isothermal magnetization (M–H) curves confirm the ferromagnetic (FM) nature of the thin film having significant hysteresis at 5 and 300 K. From the in-plane M–H curves, the saturation magnetization values are determined to be 2.1 μB/f.u. at 5 K and 1.6 μB/f.u. at 300 K, which suggest the soft FM behavior in the film having the coercive field ≈522 Oe at 5 K. The thermomagnetization measurements at 500 Oe magnetic field show the bifurcation between field-cooled and zero-field-cooled curves below about 100 K. The normalized field-cooled magnetization curve follows the T2 dependency, and the analysis reveals the Curie temperature around 335±11 K. Moreover, the low-temperature resistivity indicates semiconducting behavior with the temperature, and we find a negative temperature coefficient of resistivity (5.2×10−4/K).