Surface morphology, ferromagnetic domains and magnetic anisotropy in BaFeO3−δ thin films: Correlated structure and magnetism

(i)In addition to square structures in as-deposited film, the pyramid-shaped structures also manifest on the surface after oxygen annealing.(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.(iv) A growth of the magnetic domains with a different pattern.

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.