MAGNETIC FIELD SENSING SYSTEM USING SPIN-TORQUE DIODE EFFECT

摘要

A magnetic field sensing system with a current-perpendicular-to-the-plane (CPP) sensor, like that used for giant magnetoresistive (GMR) and tunneling magnetoresistive (TMR) spin-valve (SV) sensors, operates in a mode different from conventional GMR-SV and TMR-SV systems. An alternating-current (AC) source operates at a fixed selected frequency and directs AC perpendicularly through the layers of the CPP sensor, with the AC amplitude being high enough to deliberately induce a spin-torque in the CPP sensor's free layer. The AC-induced spin-torque at the selected frequency causes oscillations in the magnetization of the free layer that give rise to a DC voltage signal V_DC. V_DC is a direct result of only the oscillations induced in the free layer. The value of V_DC will change in response to the magnitude of the external magnetic field being sensed and as the free layer is driven in and out of resonance with the AC. The DC voltage resulting from AC-induced spin-torque oscillations of the free layer magnetization represents the actual magnetoresistive signal.