Hysteresis-free spin valves for GMR sensors

V.V. Ustinov, M.A. Milyaev, L.I. Naumova, V.V. Proglyado, T.P. Krinitsina
Institute of Metal Physics, RU

Keywords: spin valve, hysteresis, magnetic sensor


Top spin valves Ta/[FeNi/CoFe]/Cu/ CoFe/AFM/Ta based on antiferromagnetics (AFM) Fe50Mn50 and Mn75Ir25 with varying [Fe20Ni80/Co90Fe10] composite free layer parameters and Cu interlayer thickness were prepared by DC magnetron sputtering. GMR characteristics of spin valves (SV) were investigated under the conditions of non-collinear SV geometry when the applied magnetic field and pinning direction for bottom magnetic layer are non-parallel. It was shown that the value of low field hysteresis caused by free layer magnetization reversal can be reduced down to 0.1 Oe keeping the GMR ratio about 10 % by using both layers thicknesses and non-collinearity angle variation. The magnetoresistive sensitivity of non-collinear SV is about 1 %/Oe. Low-hysteresis free layer magnetization reversal is mainly due to coherent rotation of magnetization. The dependences of low field hysteresis value and GMR ratio on the Cu spacer layer thickness and the angle between applied magnetic field and pinning direction are presented.