Stress-induced effects in epitaxial (La_0.7Sr_0.3)MnO₃ films

The transport and magnetic properties of epitaxial (La_0.7Sr_0.3)MnO₃ (LSMO) films deposited on LaAlO₃ (Sample L, under a compressive stress) and SrTiO₃ (Sample S, under a tensile stress) are compared. The magnetic force microscope image of Sample L shows a 'maze-like' pattern indicating a sizable out-of-plane magnetization, while the magnetic image of Sample S shows a 'feather-like' pattern indicative of in-plane magnetization. The hysteresis loop and ferromagnetic resonance measurements indicate that the lattice mismatch between the film and the substrate is the origin of the differences in the magnetic anisotropy of the two films. Sample L has a smaller 'peak' resistivity and a larger saturation magnetization at room temperature than Sample S. Our results can be understood by the internal 'pressure' consequent upon lattice mismatch and agree qualitatively with the recent hydrostatic pressure studies on the doped manganites.