The role of strain in the magnetic properties of La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ films studied by magnetic force microscopy

In order to elucidate the role of strain in the magnetic properties of manganite films, we studied the behavior of the magnetic domains in La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ (LSMO) films grown on SrTiO$_{3}$ (STO) and NdGaO$_{3}$ (NGO) substrates, which are differently strained. Our previous studies on the magnetic properties of La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ films grown on STO substrates using magnetic force microscopy showed a distinct magnetic texture within magnetic domains, and spin reorientation and enhancement of T$_{C}$ near grain boundaries. These results were attributed to the strain in the film caused by the lattice mismatch with the substrate and the strain relaxation at the grain boundaries. Our new studies on La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ films grown on NGO substrates, which have very low strain due to a close lattice match between the film and substrate, show no presence of magnetic texture and a very sharp transition from the paramagnetic to ferromagnetic phase.