Electric-field control of magnetism using ionic liquids

Recent advances in iontronics have highlighted the electric double layer (EDL) effect as a powerful tool for controlling physical properties in condensed matter systems. When a small bias voltage is applied to an electrolyte in contact with a semiconductor or magnetic material, ions accumulate at the interface, forming an EDL that acts as a nanogap capacitor. This enables extremely high charge carrier densities—orders of magnitude higher than conventional gating— allowing efficient electric-field control of electronic and magnetic states. Importantly, two distinct mechanisms of magnetic control via EDLs have been identified. The first is a purely electrostatic effect, where accumulated charges modulate magnetic properties such as coercivity or Curie temperature through carrier injection at the interface. The second is an electrochemical mechanism, where the EDL drives the migration of oxygen ions, particularly in systems involving transition metal oxides or oxide interfaces. This leads to redox reactions that alter the oxidation states of magnetic elements, enabling reversible and non-volatile switching of magnetic anisotropy and phase states. These complementary effects have opened new avenues for spintronic applications, especially in materials where conventional doping or structural tuning is limited. Our findings demonstrate that both charge accumulation and ion migration at the interface play key roles in spinstate modulation, paving the way toward ultra-low-power and reconfigurable spintronic devices based on EDL-induced electrochemical control.