Competition between magnetic relaxation mechanisms in exchange-coupled CoO∕Co bilayers

Transverse, ac-susceptibility measurements, χ(T), of polycrystalline [Co(8nm)∕CoO(xnm); 1⩽x⩽10] bilayers are used to derive the magnetic anisotropy in an exchange-coupled ferromagnetic(FM)/antiferromagnetic(AFM) system. χ(T) was measured using the anisotropic magnetoresistance (AMR) induced by a small (≲5Oe) applied field at frequencies ranging from 40to400Hz. This low-field technique is sensitive to the full anisotropy field and to the …