Magneto-Ionic Switching of Superparamagnetism

Electrochemical reactions represent a promising approach to control magnetization via electric fields. Favorable reaction kinetics have made nanoporous materials particularly interesting for magnetic tuning experiments. A fully reversible ON and OFF switching of magnetism in nanoporous Pd(Co) at room temperature is demonstrated, triggered by electrochemical hydrogen sorption. Comprehensive magnetic characterization in combination with high‐resolution scanning transmission electron microscopy reveals the presence of Co‐rich, nanometer‐sized clusters in the nanoporous Pd matrix with distinct superparamagnetic behavior. The strong magneto‐ionic effect arises from coupling of the magnetic clusters via a Ruderman–Kittel–Kasuya–Yoshida‐type interaction in the Pd matrix which is strengthened upon hydrogen sorption. This approach offers a new pathway for the voltage control of magnetism, for application in spintronic or microelectromagnetic devices.