Boosting Room‐Temperature Magneto‐Ionics in a Non‐Magnetic Oxide Semiconductor

Abstract

Voltage control of magnetism through electric field‐induced oxygen motion (magneto‐ionics) could represent a significant breakthrough in the pursuit for new strategies to enhance energy efficiency in magnetically actuated devices. Boosting the induced changes in magnetization, magneto‐ionic rates and cyclability continue to be key challenges to turn magneto‐ionics into real applications. Here, it is demonstrated that room‐temperature magneto‐ionic effects in electrolyte‐gated paramagnetic Co3O4 films can be largely increased both in terms of generated magnetization (6 times larger) and speed (35 times faster) if the electric field is applied using an electrochemical capacitor configuration (utilizing an underlying conducting buffer layer) instead of placing the electric contacts at the side of the semiconductor (electric‐double‐layer transistor‐like configuration). This is due to the greater uniformity and strength of the electric field in the capacitor design. These results are appealing to widen the use of ion migration in technological applications such as neuromorphic computing or iontronics in general.

Voltage-driven motion of nitrogen ions: a new paradigm for magneto-ionics

“…S1-S4). The voltage actuation is carried out via electrolyte-gating using an electrochemical capacitor configuration 8 (Fig. 1a).…”

“…1a). This way, the overall film area exposed to the liquid electrolyte 26,27 is activated, establishing a well-defined out-of-plane electric field 8 . To investigate magneto-ionic motion, the films were electrolyte-gated at -50 V for 12 hours and, during this time, consecutive magnetic hysteresis loops (25 min duration each) were sequentially recorded.…”

“…Magneto-ionics [1][2][3][4][5][6][7][8][9][10][11][12][13][14] , i.e., the change in the magnetic properties of materials due to electric-fieldinduced ion motion, is acquiring a leading role, among other magnetoelectric mechanisms (intrinsic 15 or extrinsic 16 multiferroicity, electric charge accumulation [17][18][19] , to control magnetism with voltage 20,21 . This is triggered by its capability to largely modulate magnetic properties in a permanent and energy-efficient way 2,22 .…”

“…An alternative approach is to use target materials which are already oxidized. Magneto-ionics using structural oxygen (i.e., oxygen incorporated in the crystallographic structure of the actuated material) exhibits outstanding stability and reversibility 7,8 . This has been demonstrated in electrolyte-gated 17,[26][27][28][29][30] , thick (≥ 100 nm) paramagnetic Co 3 O 4 films, in which room-temperature voltage-controlled ON-OFF ferromagnetism has been achieved, benefiting from defect-assisted voltage-driven transport of structural oxygen.…”

“…Nevertheless, there is an inherent voltage trade-off between induced magnetization, speed and cyclability. Specifically, the generated magnetization increases with voltage, whereas cyclability degrades for exceedingly high voltages due to irreversible losses of oxygen (i.e., bubbling) 7,8 .…”