High-sensitive hysteresisless spin valve with a composite free layer

Abstract

Method of dc magnetron deposition has been used to prepare metallic nanostructures of the (Si, Al2O3, glass)/Ta/[NiFe/CoFe]/Cu/CoFe/(FeMn, MnIr)/Ta spin-valve type with a composite “free layer” Ni80Fe20/Co90Fe10. A three-stage method of decreasing hysteresis of the free layer has been suggested. The dependence of the magnitude of the giant magnetoresistance and hysteresis has been investigated depending on the angle between the direction of the easy magnetization axis of the free layer and the direction of the applied magnetic field in the plane of layers. It is shown that in the spin valves studied the hysteresis can be reduced to a few tenths of an oersted at the magnitude of the magnetoresistance more than 8%. In the case of a spin valve with an antiferromagnet Fe50Mn50 the magnetoresistive sensitivity in the range of the hysteresisless variation of the magnetoresistance was equal to 1%/Oe, whereas the maximum sensitivity in the presence of a hysteresis exceeded 6%/Oe. A greater sensitivity (2.5%/Oe) at the magnitude of the free-layer hysteresis of 0.6 Oe was obtained for spin valves on the basis of the antiferromagnetic Mn75Ir25 alloy. For them, the maximum magnetoresistance was equal to 11.6%.