Microstructure, colossal magnetoresistance effect and thermal infrared property of annealed La0.7Sr0.3MnO3−δ thin films on Si(100)

The La0.7Sr0.3MnO3−δ thin films were deposited on Si(100) by DC magnetron sputtering followed by annealing at 973 K for 0.5∼2 h in air/oxygen. The microstructure, room temperature reflectance and magnetoresistance (MR) of the annealed films were investigated using Glancing angle X-ray diffraction (GXRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) analyses and resistivity measurement. The results indicate that the films are single perovskite phase with distorted cubic structure. All the films show (100) preferred orientation and the degree of (100) preferred orientation depends on the annealing time and ambience. The films with highly (100) preferred orientation have a shorter Mn-O bond length. With the increase of temperature, the MR% of the films first decreases slowly in a wide temperature range, then increases and, finally, decreases rapidly. The maximum MR% of the films at 10 K and room temperature is about 73% and 7.9%, respectively. Lengthening annealing time in air cannot ensure the increase of metal-insulator transition temperature (TMI) of the films. Suitable lengthening of annealing time is propitious to the improvement of temperature stability of magnetoresistance for the films annealed in air. The higher the value TMI, the lower the room temperature emittance of the films evaluated based on reflectance.