Voltage‐driven motion of oxygen and nitrogen ions: role of defects in magneto‐ionics

Nowadays magnetoelectronic devices are still controlled by electric currents, a scheme which suffers from energy losses due to heat dissipation. Employing electrical fields as a substitution of
currents can strongly reduce ohmic losses and is expected to be crucial for energy-efficient applications. Here, a voltage-induced ionic motion (magneto-ionics) is proposed to control the magnetic properties. In traditional magneto-ionic systems oxygen or lithium are exploited as transport
ions and, only recently, nitrogen. We will demonstrate magneto-ionic effects in single-layer iron
and cobalt nitride films. Their microstructural and magnetic properties are evaluated and compared with previously studied oxides using positron annihilation spectroscopy and magnetometry
techniques. The electrolyte-gated ionic migration enables switching between paramagnetic and
ferromagnetic states. The role of vacancies and their agglomerations at grain boundaries are emphasized as diffusion channels, which allow for a fast migration and large incorporation of the
ionic species.