Magneto-ionics in mesoporous Ni-based electrodeposited films

Magnetoelectric actuation is a burgeoning topic nowadays given the need for energy-efficient devices. Magnetoelectric actuation refers to the control of magnetic properties of materials using voltage. Several mechanisms contribute to the magnetoelectric response including surface charging, ionic migration (referred to as ‘magneto-ionics’), reduction/oxidation reactions, and ferroelectric/ferromagnetic coupling.

In magneto-ionics, certain ions (e.g., oxygen, hydrogen, nitrogen, or lithium) migrate within a material when an external voltage is applied. Since electric fields, rather than electric currents, drive ionic motion, this process is more energy efficient. Potential applications of magneto-ionics include magnetic memory devices, neuromorphic computing, and adaptive magnetic materials.
Electrodeposited films, micro- and nanostructures are promising candidates for oxygen magneto-ionic investigations, particularly those with high surface-to-volume (S/V) ratios. Ferromagnetic Ni, Co and their alloys can be electrodeposited from aqueous solutions. It has been demonstrated that mesoporous Ni-Cu films with ultranarrow pore walls enable the entire film (and not just the utmost surface) to contribute to the magnetoelectric effect. This challenges the conventional ‘ultrathin-film requirement’ observed in many studies, which often necessitates expensive vacuum-based deposition techniques.

Following electrodeposition, annealing in air can transform the ferromagnetic metallic phase into a paramagnetic oxide phase. Electrolyte-gated magnetoelectric actuation of this paramagnetic material in an anhydrous, polar liquid electrolyte (e.g., propylene carbonate) enables reversible or permanent transitions between paramagnetic and ferromagnetic states via O²⁻ ion migration. The reversibility depends on the system under study and possible material modifications beyond O²⁻ motion, such as microstructural changes. From the magnetic standpoint, voltage-driven effects manifest as changes in coercivity, saturation magnetization, or magnetic anisotropy.

Within the NICKEFFECT project, we are investigating how the magnetic properties of mesoporous Ni-Co films with narrow pore walls evolve under voltage application. Additionally, we aim to determine whether the Ni/Co ratio in the initial material influences onset threshold voltages, switching rates, and saturation magnetization levels.

 

Know more about this by reading the recent scientific publication from UAB on magneto-ionic control of magnetism in Ni-Co (including several NICKEFFECT results): CLICK HERE