Itinerant-electron magnetocrystalline anisotropy energy of YCo5 and related compounds -: art. no. 184431

The contribution of the itinerant states to the magnetocrystalline anisotropy (MA) energy of YCo5 and isostructural compounds has been calculated using a fully relativistic optimized LCAO band-structure scheme within the framework of density-functional theory in local spin density approximation (LSDA), and its dependence on lattice geometry and Fe substitution has been investigated. Additionally taking into account orbital polarization, a correction to LSDA accounting for Hund's second rule. enhances the calculated orbital moments. orbital moment anisotropies and MA energies, and leads to good agreement with available experimental data for YCo5. The MA energies are found to be strongly affected by changes of the lattice geometry (cin ratio and volume) resulting from (i) uniaxial strain in YCo5 and (ii) the lanthanide contraction along the RCo5 (R = Y, La, Pr, Nd, Sm, Gd) series. because of the sensitivity of the MA energy to changes of the band structure. We obtain a large variation of the MA energy of RCo5 along the R series which is shown to be predominantly a lattice geometry effect. It is in contrast to the commonly assumed independence of the transition-metal sublattice MA on the R constituent. The calculated band-filling dependence of the MA energies of ordered Y(Co1 - xFex)(5) compounds (x=0.0.4.0.6,1.0) qualitatively explains the experimentally observed concentration dependence of the MA energy in Y(Co1 - xFex)(5) pseudobinaries at low Fe concentrations.