Photoinduced formation of ferromagnetic clusters in La0.9Ca0.1MnO3 thin films

Microwave losses due to conductivity and magnetic permeability are investig ated in La0.9Ca0.1MnO3 films illuminated with photons in the energy range o f E = 0.5-2 eV. Growth of photoinduced ferromagnetic hysteresis is observed when the magnetic field is swept between -15 and 15 mT at temperatures bel ow 60 K. The time required for saturation of the opening of the hysteresis loop depends on the photon energy having the minimum of approximate to 40 s at the illumination intensity I = 3.5 x 10(14) photons/cm(2)s. Both photoi nduced magnetization and the increase of microwave photoconductivity can be well explained with a model assuming that small ferromagnetic regions exis t within an insulating ferromagnetic phase of the sample and that these reg ions are expanded by optically induced charge transfer between Jahn-Teller split e(g) states of neighboring Mn3+ ions.