Magnetic domain structures of La0.67Sr0.33MnO3 thin films with different morphologies

Using a wide-field Kerr microscope, we have studied the magnetic domain structures of epitaxial and polycrystalline ${\mathrm{La}}_{\mathrm{0.67}}{\mathrm{Sr}}_{\mathrm{0.33}}{\mathrm{MnO}}_{\mathrm{3}}$ thin films as well as a film having thermally induced 〈110〉 microcracks. The epitaxial film on a (001) ${\mathrm{SrTiO}}_{\mathrm{3}}$ substrate has different magnetic domain behaviors for in-plane fields applied along the 〈100〉 and 〈110〉 directions. Magnetic domain orientation and contrast suggest a biaxial magnetic anisotropy with 〈110〉 easy axes. Defects such as microcracks and grain boundaries have a strong perturbing effect on the local magnetization and can lead to an enhanced and controllable spin-dependent scattering.