MR Enhancement in a Current Perpendicular-to-Plane Spin Valve by Insertion of a Ferromagnetic Layer Within the Spacer Layer

In this paper, we propose an alternative method to improve magnetoresistance by inserting a thin ferromagnetic (FM) layer into the nonmagnetic (NM) spacer of a basic spin-valve (SV) trilayer (FM1-NM-FM1), thus creating a penta-layer SV structure (FM1-NM-FM2-NM-FM1). We investigated the effect of increasing the resistivity (rho_F2) of the FM2 on overall magnetoresistance (MR). We performed both analytical and numerical studies on the MR of the current perpendicular-to-plane (CPP) structure using the phenomenological spin drift-diffusion models. For finite rho_F2 , the MR profile is dependent on the intrinsic conductance polarization (alpha_F2) of FM2. We found that inserting FM2 enhances MR when alpha_F2 exceeds a critical value of alpha_2C. It is found that MR can be doubled by inserting a FM layer with high alpha_F2, such as the half-metallic Cr ₂O. We have numerically calculated MR_max and the corresponding rho_F20 values for different alpha_F2 values. Finally, we studied the effect of spin relaxation on the MR of the CPP SV