Structural, Magnetic, and Electrical Transport Properties of Co2CrGa Full Heusler Alloy Films

Abstract

We investigated the structural, magnetic and electrical transport properties of Co2CrGa full Heusler alloy films, and optimized the growth conditions, achieving stoichiometric films. The crystalline structures and the magnetic and electrical transport properties were found to depend on the film thickness, tCCG. An ordered L21 structure was obtained for tCCG≥100 nm. The saturation magnetization decreases with decreasing film thickness and vanishes below tCCG=23 nm, indicating the existence of a magnetically dead layer in the vicinity of the substrates. For tCCG=150 nm, the saturation magnetization is 602 emu/cm3 (3.1 μB) at 5 K, which agrees very well with the theoretical value. The resistivity of the samples with tCCG≤150 nm decreases with increasing temperature, while that with tCCG=300 nm increases. By using films with tCCG=100 nm and 300 nm as bottom electrodes, forming an L21 structure, magnetic tunnel junctions (MTJs) were also fabricated, showing 5.0% and 1.4% tunnel magnetoresistance (TMR) at RT, respectively.