3-D FEM micromagnetic modeling of spin-valve sensors

Synthetic antiferromagnetic (SAF) spin-valve (SV) sensors (NiFe/Cu/Co/Ru/Co/IrMn) are studied in detail through 3-D FEM micromagnetic modeling. The current induced field, demagnetizing field and the exchange couple field are taken into account. The SAF structure is shown to have some advantages. The current field is not only helpful to bias the signal, but also to stabilize the SAF pinned layer because the current in the Co layers produces opposing fields in the layers. The thermal stability has been improved by introducing the current field. The SAF structure not only reduces the demagnetizing field in the free layer and itself, but also increases the signal dynamic range and reduces the signal distortion. These are attributed to the large antiferromagnetic coupling constant and the pinning field. Simulation results show that there is no noise-producing domain formation when the product of remanent magnetization and thickness of the hard magnets is slightly greater than that of the saturation magnetization and the thickness of the free layer.