Thickness-Dependent Magnetism in Epitaxial SrFeO_3- Thin Films

Strained oxygen-deficient perovskite SrFeO3-delta (SFO) films have been epitaxially grown by pulsed laser deposition (PLD) on SrTiO3 (STO) (001) substrates. Oxygen deficiency of the films in comparison with the stoichiometric perovskite SrFeO3 is manifested in the increased lattice parameter, c = 3.97 angstrom, the decreased mass density, rho = 4.82.5 gcm(-3), and the presence of Fe3+ cations. The SFO perovskite structure is monoclinically distorted with an increase of the film thickness, resulting in the reduction of the total magnetic moment. A wasp-waisted hysteresis loop and a negative exchange bias are observed for the 69 nm thick film due to the possible magnetic sublayers arising from a proper monoclinically distorted surface layer and a substrate-locked core layer.