# Voltage-Driven All-Solid-State Ionic Control on Co/CoO Antiferromagnet/Ferromagnet Exchange Bias

## TL;DR

This paper shows how voltage can control magnetic properties in a spintronic device using ion transport, offering a more energy-efficient alternative to traditional methods.

## Contribution

The study introduces a novel all-solid-state ionic control method for manipulating magnetic properties in antiferromagnet/ferromagnet systems.

## Key findings

- Voltage-driven oxidation of Co to CoO is reversible and stable over 1000 cycles.
- Magnetic switching in the ferromagnetic Co layer is influenced by the ionic state of the CoO layer.
- Anisotropic magnetoresistance confirms the ionic control's effect on magnetic properties.

## Abstract

Spintronics traditionally
relies on a large electric current to
create magnetic fields or spin torques to manipulate magnetic properties,
which inevitably leads to undesirable energy dissipation. Alternatively,
the voltage control of magnetism (VCM) promises significantly lower
energy costs. In the context of VCM, magneto-ionics distinguishes
itself by leveraging voltage-driven ion transport as an energy-efficient
approach to control magnetic properties, including magnetization,
coercive field, and exchange bias (EB). Herein, we demonstrate that
the voltage-driven ionic control of CoO antiferromagnetism allows
manipulation of the magnetic properties in exchange-coupled ferromagnetic
Co. In a “battery-like” device geometry, a 5 nm Co film
is precisely oxidized to realize the Co/CoO heterostructure that is
interfaced with a solid-state electrolyte and an anode-like Li ion
source. The cathode-like CoO layer reversibly converts back and forth
between Co and CoO under gate biases, even after 1000 cycles. This
subsequently influences magnetic switching in the exchange-coupled
Co layer, which is directly revealed by anisotropic magnetoresistance
(AMR) in the Co channel. Our findings demonstrate an efficient method
of all-solid-state, voltage-driven, highly reversible ionic control
on magnetic channels, offering additional dimensions of control and
mass integration capability for spintronic applications.