We investigate the exchange coupling between perpendicular anisotropy (PMA) $\mathrm{Co}/\mathrm{Pt}$ and IrMn in-plane antiferromagnets (AFMs), as well as tunneling anisotropic magnetoresistance (TAMR) in $[\mathrm{Pt}/\mathrm{Co}]/\mathrm{IrMn}/{\mathrm{AlO}}_x/\mathrm{Pt}$ tunnel junctions, where $\mathrm{Co}/\mathrm{Pt}$ magnetization drives rotation of AFM moments with the formation of exchange-spring twisting. When coupled with a PMA ferromagnet, the AFM moments partially rotate with out-of-plane magnetic fields, in contrast with being pinned along the easy direction of IrMn for in-plane fields. Because of the superior thermal tolerance of perpendicular exchange coupling and the stability of moments in $\sim 6\mathrm{nm}$-thick IrMn, TAMR gets significantly enhanced up to room temperature. Their use would advance the process towards practical AFM spintronics.

• Received 1 May 2012

DOI:https://doi.org/10.1103/PhysRevLett.109.137201