Dipole-induced magnetic anisotropy in γ-Fe2O3(001) epitaxial films

Abstract

The authors investigated the magnetic anisotropy of epitaxial films of γ-Fe2O3(001) composed entirely of Fe3+. The cubic anisotropy term (K1) was negligibly small (K1≈−2.7×104erg∕cm3), as expected for L≈0 systems; however, substantially large uniaxial anisotropy energy (Ku≈6.1×105erg∕cm3) was found as the thickness reached the bulk limit. A detailed characterization of both the in-plane and out-of-plane lattice parameters revealed that the c∕a ratio of the unit cell was intrinsically elongated due to its vacancy-ordered supercell. This unexpectedly large Ku is reasonably explained by simple dipole sums if the authors take into account the slightly stretched unit cell (c′∕a=1.03) in the growth direction even without the spin-orbit interaction.