Tunnel magnetoresistive sensors with non-hysteretic resistance–magnetic field curves using noncollinear interlayer exchange coupling through RuFe spacers

Magnetic stabilization of the ferromagnetic layers of magnetoresistive elements is a key technological requirement for fabricating highly sensitive and accurate magnetic sensors. Here, we report on a tunnel magnetoresistive (TMR) sensor wherein the free layer (FL) magnetization is stabilized by combining exchange bias, noncollinear interlayer exchange coupling through a RuFe spacer, and orange-peel ferromagnetic coupling. This method facilitates stabilization of the FL magnetization over a wide range of noncollinear angles with respect to the pinning direction by controlling the composition of the RuFe spacer. Moreover, the uniaxial anisotropy induced in the FL by annealing plays an important role in the resistance–magnetic field (R–H) curve, which was studied both experimentally and through simulation. The TMR devices exhibited negligible hysteresis even in the major R–H loops, which is promising for magnetic field-sensing applications.