Electronic transport in reactively sputtered Mn3GaN films prepared under optimized nitrogen flow

Abstract

Mn-based nitrides with antiperovskite structures have several properties that can be utilized for antiferromagnetic spintronics. Their magnetic properties depend on the structural quality, composition and doping of the cubic antiperovskite structure. Such nitride thin films are usually produced by reactive physical vapor deposition, where the deposition rate of N can only be controlled by the N₂ gas flow. We show that the tuning of the N content can be optimized using low temperature resistivity measurements, which serve as an indicator of the degree of structural disorder. Several Mn₃GaN_x films were prepared by reactive magnetron sputtering under different N₂ gas flows. Under optimized gas flow conditions, we obtain films that exhibit a metal-like temperature dependence of the resistivity, a vanishing logarithmic increase of the resistivity towards zero, the highest resistivity ratio, and a lattice contraction of 0.4% along the growth direction when heated above the Néel temperature TN. The retarded formation of an additional magnetic phase appearing at a temperature T∗≪TN gives rise to a large thermal hysteresis of the resistivity and anomalous Hall effect.