Magnetization-induced second-harmonic generation of La0.7Sr0.3MnO3 thin films grown by RF magnetron sputtering method

Magnetization-induced second-harmonic generation (MSHG) scanning microscopy and spectroscopy are used to explore the nonlinear magneto-optical properties of La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ thin films at room temperature. The thin film is deposited on single crystalline LaAlO$_{3}$ (100) substrate by a RF magnetron sputtering system at room temperature and then annealed at 900\r{ }C in flowing O$_{2}$ for one hour. The temperature dependent magnetization measurement indicates its ferromagnetic transition temperature T$_{c}$ around 360 K. The X-ray diffraction shows that its crystal structure is orthorhombic and its c-axis is along the surface normal. However, our MSHG measurements reveal the existence of individual LSMO micrograins, which have their c-axis orientation different from the surface normal. These particular LSMO micrograins can proceed a large nonlinear Kerr rotation with a low external magnetic field. We attribute this phenomenon to the probable anisotropic spin-flipping process inside the single micrograin.