Effect of growth temperature on structural, magnetic, and transport properties of Co2Cr0.6Fe0.4Al Heusler alloy sputtered thin films

Abstract

The effect of growth temperature TS on crystallographic structure, DC-magnetization, and electrical transport behavior of pulsed dc-magnetron sputtered Co2Cr0.6Fe0.4Al Heusler alloy thin films has been investigated. The increase in TS enhances the crystallite size, structural ordering in these films, eventually resulting in the increase in saturation magnetization to 2.4 μB/f.u. The (220) textured growth of thin films induces an in-plane magnetic anisotropy of ∼2.1 × 104 erg/cc in these films. The improvement in structural ordering is accompanied with the systematic increase in resistivity ratio ρ(300)/ρ(20 K) and also with the change in sign of temperature coefficients of resistivity from negative to positive at TS = 500 °C. In addition, a resistivity minimum is observed at low temperature in the films deposited at TS>400 °C. The resistivity behavior at low temperature is governed by e-e scattering (T2 dependence), one-magnon scattering (T3 dependence), and weak localization effect (T1/2). However at higher temperature, the resistivity behavior is governed by Tn power law, and the value of n was found to be 1.35 and 0.91 for the films grown at 500 and 600 °C, respectively. The anomalous Hall Effect studies revealed the presence of side-jump scattering mechanism in Hall resistivity consistent with the structural, transport, and DC-magnetization measurements. Nearly, temperature independent Hall sensitivity behavior is observed for these samples in a moderate field range from 0 to 0.3 T, which shows the suitability of the material for developing Hall sensors.