Reduction of AMR effect in giant magnetoresistance spin valve structures

For spin valve heads, the conventional anisotropic magnetoresistance (AMR) effect deteriorates the linearity of transfer curves and degrades its performance. This problem is more severe for thicker free layer spin valve. In this paper, giant magnetoresistance (GMR) and AMR effect of a spin valve structure with laminated free layer (seed/Fa/I/Fb/Cu/AP1/Ru/AP2/AFM/cap, I is a thin high resistive layer) were calculated using semiclassical transport model. It is found that the GMR of spin valve structure with laminated free layer is reduced slightly and DR is comparable with the standard one due to the increase of the sheet resistance. The AMR of the laminated free layer reduced dramatically due to the effective magnetic thickness reduction. Therefore, the AMR/GMR ratio in spin valve was greatly reduced. Film level experimental data confirmed the simulation results. As an example, the AMR of 80 Å, 65 Å thickness free layer reduced from 1.6, 1.2% to 0.74, 0.6%, respectively, while GMR ratio reduced slightly due to lamination of free layer. The AMR effect of spin valve structure can be reduced by 50% through the lamination of the free layer. It can be expected that the linearity of the transfer curves can be improved greatly