Coupling mechanisms in exchange biased films (invited)

We use an atomistic Heisenberg model in conjunction with the classical Landau Lifshitz equation for the spin motion to study coupling mechanisms between ferromagnetic (FM) and antiferromagnetic (AFM) films. Calculations for CoO/FM illustrate that there are two coupling mechanisms at work, the spin–flop coupling and an AFM–FM coupling through uncompensated defects. While the latter accounts for exchange bias and related phenomena, the former gives rise to a large coercivity and perpendicular alignment between FM spins and AFM easy axis. A combination of the two mechanisms explains apparent discrepancies between reversible and irreversible measurements of the AFM–FM coupling.