Effect of three-dimensional strain states on magnetic anisotropy of La0.8Ca0.2MnO3 epitaxial thin films

Magnetic anisotropy of ${\mathrm{La}}_{\mathrm{0.8}}{\mathrm{Ca}}_{\mathrm{0.2}}{\mathrm{MnO}}_{\mathrm{3}}$ (LCMO) epitaxial thin films grown on (001) ${\mathrm{SrTiO}}_{\mathrm{3}}$ and ${\mathrm{LaAlO}}_{\mathrm{3}}$ a substrates exhibits strong correlation with substrate-induced strain states as determined by normal and grazing incidence x-ray diffraction. In a 250 Å thick LCMO ${\text{(001)}}^T$ film grown on ${\mathrm{SrTiO}}_{\mathrm{3}}$ substrate, an in-plane biaxial magnetic anisotropy is observed, and it is accompanied by a substrate-induced in-plane biaxial tensile strain. In contrast, the observed magnetic easy axis for a 250 Å ${\text{(110)}}^T$ film grown on ${\mathrm{LaAlO}}_{\mathrm{3}}$ substrate is perpendicular to the film plane, and the corresponding in-plane strain is biaxial compressive. In both cases the magnetic easy axes are along the crystallographic directions under tensile strain, indicating the presence of a positive magnetostriction. In thicker films (∼4000 Å) grown on both substrates that are nearly strain relaxed, the magnetic easy axis lies in the film plane along the [110] direction of the (001) substrate.