Enhancement of low-field magneto-dielectric response in two-dimensional Co/AlF granular films

Abstract

We report enhanced low-field magneto-dielectric (MD) response in two-dimensional (2D) Co/Al fluoride (AlF) granular films, which comprise 2D crystalline Co granules laminated by AlF amorphous layers. We observed an increase in MD sensitivity under a low magnetic field as the Co layer thickness increased. A small magnetic field (H = 1000 Oe) resulted in a large MD ratio, up to Δε′/ε′ = 0.8% in Co (3 nm)/AlF (5 nm) films. The low-field enhancement was determined to be caused by increasing the granule size and pair density and by the balance between the superparamagnetic and ferromagnetic components in the magnetic granular layers. The 2D granular structure opens another avenue for tailoring magneto-electric properties in high-performance MD devices at room temperature.