Controlling the magnetic alignment at the MnGa/Co2MnSi interface: A DFT study

Abstract

The MnGa/Co2MnSi is a common electrode in Magnetic Tunnel Junctions (MTJ). We study the MnGa/Co2MnSi interfaces using spin-polarized Density Functional Theory. We have focused on the interface stability and the effect of the interface arrangements -at the atomic scale- on its electronic and magnetic properties. Depending on how the atomic species interact at the interface, the MnGa/Co2MnSi electrode can show either antiferromagnetic or ferromagnetic behavior, modulating the spin transfer through the system. Antiferromagnetic ordering appears due to Mn-Mn interlayer interactions across the MnSi-Mn interface and is thermodynamically stable for Co-poor and Mn-rich growth conditions. Mn atoms have magnetic moments of −2.97 μB and 2.31 μB. On the other hand, a ferromagnetic behavior could be engineered under Co-rich and Mn-poor conditions, as demonstrated by the interface formation energy analysis. Such magnetic ordering emerges at the Co-Ga interface since direct Mn-Mn interlayer interactions disappear; Mn atoms have magnetic moments of ∼ 3.00 μB and ∼ 2.8 μB for the Co2MnSi and MnGa films, respectively. Our findings lay the foundations to guide experimental efforts in designing electrodes that could potentially generate efficient tunneling behavior in perpendicular Magnetic Tunnel Junctions, which are the heart of novel MRAMs.