Tunneling Magnetodielectric Effect in Co–Al₂O₃ Granular Films

In this study, we investigated the tunneling magnetodielectric (TMD) effect in cobalt–aluminum-oxide (Co–Al2O3) nanogranular films. The films showed a homogeneous granular structure composed of nanometer Co granules dispersed in an Al2O3 matrix and demonstrated a TMD response with a maximum TMD ratio {(ε′H=850kA/m − ε′H=0kA/m)/ε′H=0kA/m} of 1.1% at a frequency of 5.0 MHz at room temperature. These results show the existence of the TMD effect in the magnetic metal–oxide composite, which would promote the wide applications of the magnetic metal–oxide nanogranular materials in magnetoelectric devices.