MAGNETIC-ANISOTROPY OF EPITAXIAL CO MN SUPERLATTICES - AN ANGULAR-DEPENDENT FERROMAGNETIC-RESONANCE STUDY/

The magnetic anisotropy of epitaxial [Co-24 Angstrom/Mn(t(Mn))](12) su perlattices is studied as a function of the Mn layer thickness by mean s of ferromagnetic resonance. For fixed cobalt layer thickness one fin ds a transition from a (111) fcc to a (0001) hcp cobalt structure at a critical thickness of 10-12 Angstrom for the Mn layers, This is seen from the sharp increase of the uniaxial magnetocrystalline anisotropy from nearly zero to 2 X 10(6) erg/cm(3) A similar enhancement of the p erpendicular to in-plane resonance linewidth by a factor of 4 indicate s a strong increase of the number of structural defects. The complete out-of-plane angular dependence of the resonance field yields the seco nd- and fourth-order uniaxial magnetic anisotropy constants whereas th at of the ferromagnetic resonance linewidth gives a measure of the mag netic homogeneity. The experimental results are well explained by a th eoretical model which allows us to estimate the number of defects with in the Co layers and to discuss their origin.