Interfacial exchange coupling between transition metals and Mn1.5Ga studied by X-ray magnetic circular dichroism

We investigated the element-specific magnetic properties at interfaces of Fe (1 nm)/Mn1.5Ga and Co (1 nm)/Mn1.5Ga using X-ray magnetic circular dichroism (XMCD). We found that the spins in the Fe and Co layers were coupled with and parallel to those in the Mn1.5Ga under the as-grown conditions, while the post-annealing at 350 °C changed the interface magnetic coupling to antiferromagnetic in Co. The element-specific hysteresis curves at each XMCD absorption edge revealed large coercive fields in Fe and Co through the exchange coupling with Mn1.5Ga. After the annealing process, XMCD spectral line shapes indicate that the interfacial reactions promote the formation of Mn2CoGa-like secondary alloys, which influences the performance of tunnel magnetoresistance using the interfaces between transition metals and MnGa.