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Exchange bias and coercivity are investigated in antiferromagnetic (AFM)/ferromagnetic (FM) bilayers by steepest descent and Monte Carlo simulations. For a given range of the AFM anisotropy, a magnetic domain wall parallel to the interface is created in the AFM layer. This domain wall propagates along the AFM thickness and eventually gets pinned at the negative saturation due to the intrinsic Peierls potential of the AFM material. We demonstrate that this pinning and its associated dissipation is one possible source of coercivity in such exchange coupled bilayers. Monte Carlo simulations were also carried out to investigate the influence of thermal fluctuations, which induce a random walk of the domain wall throughout the AFM layer, leading to magnetic aftereffect. Depending on the experimental characteristic measurement time and temperature, the domain wall can eventually be expelled from the AFM layer leading to the reversal of the entire AFM spin lattice. This contribution to the exchange bias phenomenon particularly explains quite well the enhancement of coercivity in exchange coupled bilayers at low temperature, even in polycrystalline samples. [ABSTRACT FROM AUTHOR]

The perpendicular magnetic anisotropy (PMA) arising at the interface between ferromagnetic transition metals and metallic oxides was investigated via first-principles calculations. In this work very large values of PMA, up to 3 erg/cm2, at Fe∣MgO interfaces are reported, in agreement with recent experiments. The origin of PMA is attributed to overlap between O-pz and transition metal dz2 orbitals hybridized with dxz(yz) orbitals with stronger spin-orbit coupling-induced splitting around the Fermi level for perpendicular magnetization orientation. Furthermore, it is shown that the PMA value weakens in the case of over- or underoxidation due to the fact that oxygen pz and transition metal dz2 orbital overlap is strongly affected by disorder, in agreement with experimental observations in magnetic tunnel junctions. [ABSTRACT FROM AUTHOR]