Ab initio study of magneto-ionic mechanisms in ferromagnet/oxide multilayers

The application of gate voltages in heavy metal/ferromagnet/oxide multilayer stacks has been identified as one possible candidate to manipulate their anisotropy at will. However, this method has proven to show a wide variety of behaviors in terms of reversibility, depending on the nature of the metal/oxide interface and its degree of oxidation. In order to shed light on the microscopic mechanism governing the complex magneto-ionic behavior in Ta/CoFeB/HfO2, we perform ab initio simulations on various setups comprising Fe/O and Fe/HfO2 interfaces with different oxygen atom interfacial geometries. After the determination of the more stable interfacial configurations, we calculate the magnetocrystalline anisotropy energy on the different unit cell configurations and formulate a possible mechanism that well describes the recent experimental observations in Ta/CoFeB/HfO2.