Angular-dependent tunneling magnetoresistance in a tunnel junction with ferromagnetic and noncollinear antiferromagnetic electrodes

Magnetic tunnel junctions (MTJs) based on ferromagnetic (FM) metal electrodes exhibit a tunneling magnetoresistance (TMR) effect, which can be well understood using a model of two spin-conduction channels and spin conservation in the tunneling process. Recently, TMR has been predicted and observed in antiferromagnetic (AFM) tunnel junctions (AFMTJs) based on noncollinear AFM electrodes, promising for high-speed and high-density spintronic applications. These findings challenge the conventional mechanism of TMR due to generally no spin conservation in noncollinear AFM metals. Here, we explore spin-polarized tunneling in an $\mathrm{M}{\mathrm{n}}_{3}\mathrm{GaN}/\mathrm{SrTi}{\mathrm{O}}_{3}/\mathrm{SrRu}{\mathrm{O}}_{3}$ (001) MTJ, where the reference layer is a noncollinear AFM $\mathrm{M}{\mathrm{n}}_{3}\mathrm{GaN}$ electrode and the free layer is a collinear FM $\mathrm{SrRu}{\mathrm{O}}_{3}$ electrode. Based on quantum-transport calculations, we predict that the rotation of FM magnetization of $\mathrm{SrRu}{\mathrm{O}}_{3}$ leads to the angular-dependent TMR being largely controlled by the matching of the average momentum-dependent spin polarization of the two electrodes. These results demonstrate that despite broken spin conservation in the tunneling process, the momentum-dependent spin polarization of the electrodes is a valuable quantity which can be used for elucidating TMR in MTJs with noncollinear AFM electrodes.