A trial for fabricating a spin-filter operating at room temperature using a ferromagnetic insulator

In this study, we attempt to develop a spin-filtering device using a ferromagnetic barrier which works at room temperature. We use CoFe₂O₄ as a ferromagnetic insulator, which is considered as a fully-spin polarized ferromagnet. Due to its high Curie temperature, this device is expected to work at room temperature. Both CoFe₂O₄ thin films and tunnel junctions with a CoFe₂O₄ barrier were fabricated on thermally oxidized Si and MgO [110] single crystal substrates by RF-magnetron sputtering. The tunnel junctions consists of TiN/CoFe₂O₄/Al and TiN/CoFe₂O₄/Ni₈₀Fe₂₀. Crystal structure of the films were characterized by X-ray diffraction (XRD), magnetic properties were measured by vibrating sample magnetometers (VSM) and chemical states of the films were determined by X-ray photoelectron spectroscopy (XPS). The resistance (R)-field (H) curves are measured in spin-filtering devices with a new nm thick CoFe₂O₄ barrier by the DC four probe method.