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Abstract: We have studied the structure, the surface morphology, the magnetic domains and the magnetization of ferromagnetic BaFeO3−δ (BFO) thin films deposited on single-crystal MgO (001) substrate. The BFO film is ferromagnetic-insulating at room temperature and shows a growth of self organized symmetric square-shaped structures of various length-scales on the surface. The film, after oxygen annealing, shows several pronounced modifications: (i) in addition to square structures, the pyramid-shaped structures also manifest on the surface, (ii) the lattice parameter decreases indicating a change in the structure, (iii) the magnetization isotherms show magnetic anisotropy with a five-fold increase in magnetic coercivity and two-fold increase in magnetic moment, and (iv) a larger growth of the magnetic domains. These results demonstrate a strong influence of oxygen annealing on structural and magnetic properties of BFO films. Our results suggest that the structural and the magnetic properties are strongly correlated in BFO films, albeit with unaltered insulating state. [Copyright &y& Elsevier]

Abstract: The magnetic and electronic ground states of the polycrystalline perovskite compound La0.7Sr0.3Co0.9Mn0.1O3 have been studied using AC susceptibility, resistivity and neutron depolarization techniques. Results of neutron depolarization study establish the existence of ferromagnetic domains of ∼3μm size below 180K. The substitution of 10at% Mn ions at the Co site in the compound La0.7Sr0.3CoO3 reduces the effective eg electron transfer and suppresses the double exchange interaction. The competition between the reduced ferromagnetic double exchange interaction and the coexisting antiferromagnetic interaction along with the random nature of substitution leads to a randomly canted ferromagnetic ground state for the substituted compound. Resistivity study confirms that the randomly canted ferromagnetic ground state is insulating. [Copyright &y& Elsevier]