MnGa tunnel junctions*

Magnetic Weyl semimetals are favorable candidates for magnetic tunnel junction (MTJ) electrodes due their topologically nontrivial band structures and chirality-magnetization locking mechanism. However, the tunneling magnetoresistance (TMR) of MTJs with ferromagnetic Weyl semimetal electrodes has not yet been fully explored. In this work, we study the full Heusler alloy Co₂MnGa, which exhibits unique bulk Weyl fermion lines as well as drumhead surface states. We grow topological L2₁ phase Co₂MnGa thin films and Co₂MnGa/MgO/Co₂MnGa MTJs via heated magnetron sputtering and post-annealing. The TMR of the MTJs is dependent on the heating and annealing temperature, as well as the stage at which we heat up the sample. We also measure the anomalous Hall signals to characterize the proportion of topological phase in the Co₂MnGa thin films. Our results indicate that the topological band structures of Co₂MnGa could play a role in increasing the TMR of Co₂MnGa MTJs. With further optimization and material engineering, it is possible to realize even higher TMR using magnetic Weyl semimetals.