Electric and Magnetic Properties of BiFe_1-xMn_xO₃ Thin Films and CaFeO_x/BiFe_1-xMn_xO₃ Superlattices

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The BiFe_1-xMn_xO₃(BFMO) film shows monoclinic structure distorted along the <110> direction, while high quality [CaFeO₃(CFO)/BFMO] superlattice grows with tetragonal structure, lattice parameter of which in-plane is fit to that of Nb doped SrTiO₃(001) substrate. The BFMO film and the [CFO/BFMO] superlattice show similar M-H curves and saturation magnetic moment as a function of temperature. Magnetic moment rapidly increases in low magnetic field region and then gradually develops and saturated in high field region at 10 K. At 300 K, magnetic moment saturates in low magnetic field. As a temperature increases, saturation magnetic moment per magnetic ion rapidly decreases above 10K, and then gradually reduces. The magnetic moment at 300K of BFMO is 0.107μ_B higher than 0.034μ_B detected in the [CFO/BFMO] superlattice, probably due to the thin BFMO layer in the superlattice. Estimated T_C of the BFMO film and the superlattice is 600 K and 500K, much higher than room temperature. Leakage current behavior indicates the Fowler-Nordheim tunneling and Schottky emission at Au/BFMO interface and Poole-Frenkel hopping conduction in the BFMO layer.