Temperature, Bias, Angle, and Thickness-Dependent Magnetoresistance in a Vertical Spin Valve Structure CoFe/TiO2/CoFe

Metal-oxide spin valve junctions are the building blocks for spintronic devices and are to be utilized for miniaturized magnetic sensors. Here, the fabrication and characterization of the vertical spin valve (VSV) based on the CoFe/TiO2/CoFe structure are described. A spacer layer (TiO2) of different thicknesses in the spin valve is utilized and the effect on MR is studied. This VSV showed significant positive magnetoresistance (MR) at different temperatures from low to room temperature. The maximum value of tunneling MR is investigated to be 3.4% at 30 K and 1.03% at room temperature (300 K), and the spin polarization obtained at 30 K is 12.8%. The MR of the spin valve is investigated by changing the orientation of the device at different angles with respect to an applied magnetic field, the switching points shifted toward the higher magnetic fields and the signal became wider. Interestingly, a negative tunneling MR is observed when the thickness of the spacer layer (TiO2 = 5.5 nm) is enhanced which may be due to the spin filtering effect. The demonstrated devices identify TiO2 as favorable spacer material in spin valves and open a way to integrate high-performance memory storage devices.

Automated summary

This paper presents the fabrication and characterization of vertical spin valve based on CoFe/TiO2/CoFe structure. The effect of TiO2 thickness on magnetoresistance (MR) is studied and TiO2 is identified as a favorable spacer material. Additionally, a negative tunneling MR is observed, possibly due to the spin filtering effect.