MAGNETIC ANISOTROPIES AND EXCHANGE COUPLING IN ULTRATHIN FCC CO(001) STRUCTURES

Metastable fcc structures using ultrathin layers of metastable fcc Co(001) and fcc Cu(001) were grown by molecular-beam epitaxy. The growth was studied using reflection high-energy electron-diffraction (RHEED) patterns and RHEED intensity oscillations. The magnetic properties were investigated by employing ferromagnetic-resonance (FMR) and surface magneto-optic Kerr effect (SMOKE) techniques. A detailed discussion of the underlying physical mechanisms in FMR and SMOKE studies is presented. The temperature and thickness dependences of the perpendicular uniaxial and fourfold in-plane anisotropies are given and discussed. The role of lattice strains in magnetic anisotropies is demonstrated. FMR measurements revealed that the magnetic properties of single Co layers are different from those in Co/Cu/Co trilayers because of a lattice-strain relaxation in the multilayer samples. The exchange coupling between fcc Co(001) layers separated by a fcc Cu(001) interlayer was studied for several structures. The exchange coupling in Co structures was found to be anisotropic. Hysteresis loops were measured by means of SMOKE. Magnetic-trilayer hysteresis loops are complex. Micromagnetic calculations were carried out to explain their main features.