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

TL;DR

This study uses ab-initio simulations to explore the microscopic magneto-ionic mechanisms in ferromagnet/oxide multilayers, shedding light on how interface chemistry affects magnetic anisotropy control via gate voltages.

Contribution

It provides a detailed ab-initio analysis of interface configurations and their impact on magnetic anisotropy, offering a microscopic understanding of magneto-ionic effects in multilayers.

Findings

Identified stable interfacial configurations affecting anisotropy.

Calculated magnetic anisotropy energies for various setups.

Proposed a mechanism explaining experimental behaviors.

Abstract

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 behaviours 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 behaviour in $\text{Ta/CoFeB/}\text{HfO}_2$, we perform ab-initio simulations on various setups comprising $\text{Fe/O, Fe/HfO}_2$ interfaces with different oxygen atom interfacial geometries. After the determination of the more stable interfacial configurations, we calculate the magnetic anisotropy energy on the different unit cell configurations and formulate a possible mechanism that well describes the recent experimental observations in $\text{Ta/CoFeB/}\text{HfO}_2$.