Antiferromagnetic magnetization and exchange anisotropy in ferromagnetic/antiferromagnetic/ferromagnetic trilayers

Phases of antiferromagnetic magnetization and exchange bias and coercivity in ferromagnetic/antiferromagnetic/ferromagnetic (FM/AF/FM) trilayers with interface quadratic and biquadratic exchange coupling are studied comprehensively. Three possible cases are found, namely reversible recovering case, irreversible continuously-reversing case and irreversible discontinuously-reversing case. Realization of the cases strongly depends on pinned-MFM interface quadratic exchange coupling J1, free-MFM interface quadratic exchange coupling J2 and biquadratic coupling J2'. In the reversible recovering, the exchange coupling results in an exchange bias, and there is no exchange bias in other cases. It provides possible explanation for both hysteresis energy loss and perpendicular coupling at the interface.