Stabilizing Perpendicular Magnetic Anisotropy with Strong Exchange Bias in PtMn/Co by Magneto-Ionics

Electric field control of magnetic properties offers a broad and promisingtoolbox for enabling ultra-low power electronics. A key challenge with hightechnological relevance is to master the interplay between the magneticanisotropy of a ferromagnet and the exchange coupling to an adjacentantiferromagnet. Here, we demonstrate that magneto-ionic gating can be used toachieve a very stable out-of-plane (OOP) oriented magnetization with strongexchange bias in samples with as-deposited preferred in-plane (IP)magnetization. We show that the perpendicular interfacial anisotropy can beincreased by a factor of 2.2 in the stack Ta/Pt/PtMn/Co/HfO2 by applying -2.5 Vgate voltage over 3 nm HfO2, causing a reorientation of the magnetization fromIP into OOP with a strong OOP exchange bias of more than 50 mT. Comparing twothicknesses of PtMn, we identify a notable trade-off: while thicker PtMn yieldsa significantly larger exchange bias, it also results in a slower response toionic liquid gating. These results pave the way for post-deposition electricaltailoring of magnetic anisotropy and exchange bias in samples requiringsignificant exchange bias.