Combining High Thermal Stability of MnNi Antiferromagnets With High-Performance MgO-TMR Sensors Through Texture Engineering With Ion Beam Assisted Deposition

Tunneling magnetoresistive (TMR) sensors with enhanced thermal resilience are being pursued for harsh environment applications. In this letter, we explore MnNi as a possible candidate for exchange bias in TMR sensor multilayers. We use ion beam assisted deposition for MnNi layer growth. A significant emergence of exchange bias field of $\mu _{0}H_{\text{ex}} =$ 110 mT was obtained in MnNi/CoFe bilayers against the ion beam deposited counterpart. In addition, we demonstrate for the first time in literature the compatibility with state-of-the-art sensor multilayers comprising synthetic antiferromagnets and MgO tunnel barriers. The optimized device shows a tunneling magnetoresistance ratio of 130 $\%$ at RT and a 30 $\%$ at 300 $^\circ$ C corresponding to sensitivities of 17.0 and 9.5 $\%$ /mT with well-defined parallel/antiparallel plateaus in the full-temperature operation window.