Magnetization processes in exchange-coupled nano-crystalline Fe/Co planar systems

Single element Co and Fe thin films and Co/Fe/Co trilayers with constant Co-layer thickness were e-beam evaporated in UHV. The samples show a nano-crystalline nature. The trilayers display a rigid composite magnet behavior, i.e., a single-phase-like hysteresis loop. The Co single film and the Co/Fe/Co trilayers show a well-defined uniaxial in-plane anisotropy. In the trilayers, anisotropy is enhanced on increasing Fe-layer thickness. This phenomenon is understood in terms of competing surface and volume contributions from Co/Fe interface and Co magnetocrystalline anisotropy.