TMR Reference Unit With Anti-Parallel MTJ For Multi-Axis Sensing

The patent employs a composite magnetic structure combining perpendicular magnetization pinned layers with in-plane magnetization free layers. This composite approach allows the TMR sensor to achieve both high sensitivity (through TMR effect) and multi-axis sensing capability (through perpendicular anisotropy enabling out-of-plane magnetization rotation), resolving the contradiction between sensitivity and adaptability.

The patent changes the magnetization orientation parameter from purely in-plane to perpendicular-out-of-plane by introducing perpendicular magnetic anisotropy (PMA) in the pinned layers. This parameter change enables the free layer magnetization to rotate in three-dimensional space, providing multi-axis sensing capability while maintaining high sensitivity through the TMR effect.

The patent designs the TMR reference unit with symmetric anti-parallel magnetization configuration where the two MTJ devices automatically compensate for each other's drift and environmental effects. This self-balancing mechanism maintains zero-field reference stability without requiring external bias current or magnetic shielding, eliminating additional power consumption while ensuring reference reliability.

The patent uses two MTJ devices with anti-parallel magnetization configurations that act as counterweights to each other. The symmetric structure ensures that environmental variations and drift affect both devices equally, allowing automatic cancellation of these effects and maintaining stable zero-field reference without additional power-consuming compensation mechanisms.