Microstructural and magnetic properties of (La0.7Sr0.3MnO3)0.7:(Mn3O4)0.3 nanocomposite thin films

Epitaxial (La0.7Sr0.3MnO3)(0.7):(Mn3O4)(0.3) (LSMO:Mn3O4) nanocomposite thin films were grown on SrTiO3 (001) substrate by a pulsed laser deposition technique. The nanocomposite structures vary from triangular domains, to vertically aligned columns, and finally to smaller spherical domains as the deposition frequency varies from 1, 5, to 10 Hz, respectively. The strain in LSMO is systematically tuned, but that of the Mn3O4 phase is relatively stable as the deposition frequency increases. The tunable strain is found directly related to the different domain and grain boundary (GB) structures. Physical properties including saturation magnetization, Curie temperature (T-C), magnetoresistance and metal-insulator transition temperature (T-MI), all show systematic trends as the deposition frequency varies. This study reveals that the domain/GBs tunability achieved in nanocomposite thin films can affect the lattice strain and further tune their ferromagnetic properties. (C) 2011 American Institute of Physics. [doi:10.1063/1.3552594]