Magnetic property modulation in sputter-grown BaTiO3-Y3Fe5O12 composite films

Abstract Herein, we present the structural and magnetic properties of composite thin films consisting of garnet-structured Y3Fe5O12 and perovskite-structured BaTiO3 on SrTiO3 (001) substrates, obtained by sputtering and sequential heat treatment. The BaTiO3-Y3Fe5O12 thin films deposited at room temperature exhibited an amorphous phase with negligible magnetization, whereas the post-annealed films showed a self-assembled composite structure in which BaTiO3 grew with the same crystallographic orientation within the Y3Fe5O12 matrix. The magnetic hysteresis loops of the annealed thin films revealed two distinct slopes at room temperature. The steeper slope near the zero field originated from the soft magnetic Y3Fe5O12, whereas the smaller slope originated from the secondary phase of the hard magnetic BaFe12O19. The formation of the secondary phases, YFeO3 and BaFe12O19, was clearly confirmed by high-resolution transmission electron microscopy and elemental mapping. However, the composite thin films grown at 650 °C displayed a different surface morphology and single-phase switching in the magnetic hysteresis loops after annealing. This new report on single- or multi-switching in perovskite-garnet composite thin films is a promising development in the design of multi-bit memory devices.