0.5Ca 0.5MnO 3 films prepared by laser molecular beam epitaxy]]>

摘要

AbstractWe present a structure, surface morphology and electrical study of ultrathin epitaxial La0.5Ca0.5MnO3(LCMO) films (2-100 unit cells) grown by laser molecular beam epitaxy. The films are cube on cube epitaxial with respect to the SrTiO3(STO) substrate confirmed by x-ray analysis. When the film thickness is increased, the resistivity decreases drastically while no important surface changes are observed. Single crystalline substrates: STO, LaAlO3(LAO) and (La,Sr) (Al,Ta)O3are used to investigate the strain related surface microstructure and electrical properties. Different surface morphology and transport behaviors are observed in the 10 unit cells thick LCMO films with different strain type. The comparison among the films on different substrates indicates that the films under compressive strain (on LAO) exhibit the smoothest surface, the lowest resistivity and the highest magnetoresistance, while those under larger tensile strain (on STO) show a contrary behavior. The strain-related transport behaviors in the multi-phase competing LCMO system are interpreted on the basis of different Jahn-Teller distortion and relative size of the ferromagnetic-metal region for the films under different strain.Highlights