Title: Giant perpendicular exchange bias with antiferromagnetic MnN,
Abstract: We investigated an out-of-plane exchange bias system that is based on the
antiferromagnet MnN. Polycrystalline, highly textured film stacks of Ta / MnN /
CoFeB / MgO / Ta were grown on SiO$_x$ by (reactive) magnetron sputtering and
studied by x-ray diffraction and Kerr magnetometry. Nontrivial modifications of
the exchange bias and the perpendicular magnetic anisotropy were observed both
as functions of film thicknesses as well as field cooling temperatures. In
optimized film stacks, a giant perpendicular exchange bias of 3600 Oe and a
coercive field of 350 Oe were observed at room temperature. The effective
interfacial exchange energy is estimated to be $J_\mathrm{eff} = 0.24$ mJ/m$^2$
and the effective uniaxial anisotropy constant of the antiferromagnet is
$K_\mathrm{eff} = 24$ kJ/m$^3$. The maximum effective perpendicular anisotropy
field of the CoFeB layer is $H_\mathrm{ani} = 3400$ Oe. These values are larger
than any previously reported values. These results possibly open a route to
magnetically stable, exchange biased perpendicularly magnetized spin valves.