Evolution of magnetic anisotropy in La0.67Sr0.33MnO3 thin films due to the appearance of out-of-plane magnetization at low temperature

Abstract

We have observed quadrupolar angle-dependent anisotropic magnetoresistance (AMR) at low temperature in La0.67Sr0.33MnO3 (LSMO) films grown on SrTiO3 substrate, where the magnetic field was applied while rotating the direction of the applied magnetic field from out-of-plane (OP) to in-plane. At room temperature, the easy axis is in-plane and has a two-fold magnetic anisotropy. As the temperature decreases, it changes to a quadrupolar anisotropy. Along with the AMR, we have measured the magnetoresistance (MR) in the OP direction at various temperatures. Like the AMR, we found the appearance of a new magnetic configuration in the OP direction at low temperatures. We suggest that one of the important origins of the new OP magnetism, which appears at temperature much lower than the Curie temperature (Tc), is the d3z2−r2 orbital at the interface between the LSMO films and SrTiO3 substrate. It has been reported that despite the tensile strain imposed by the SrTiO3 substrate, the d3z2−r2 orbital exists at the interface and causes the OP magnetism. We demonstrate by a polarized x-ray resonant scattering that there is a higher density of d3z2−r2 orbitals at the interface than in the region away from the interface. As other references have proposed, we suggest the orbital reconstructions and the orbital reconstruction-driven magnetic reorientation at the interface as the origin of the appearance of the OP magnetism present in the AMR and MR results.