Optimizing the Magnetic Properties of Cascaded Spin Valve Ellipses for Magnetic Field Sensors

The spin valve (SV) based field sensor has better signal output than anisotropy magnetoresistance (AMR) sensor. A SV multilayer with an in-plane magnetization anisotropy consisting of Ta 2/ IrMn 10/ CoFe 2.5 / Cu 2/ CoFe 2 / NiFe 2.5/ Ta 5 (thickness in nanometers) is prepared by means of sputtering. A field cooling at 550 K under an external magnetic field of 2 KOe is then employed. Nano-patterning is carried out by using a standard electron beam lithography in conjunction with ion-milling etching technique. A standard four-terminal ac lock-in measurement is employed to characterize the reversal behaviors. We find the reversal behaviors of cascaded SV device can be controlled by gap value and field cool again.