Magneto-dielectric properties of in-situ oxidized magnesium-aluminium spinel thin films using electrodeposition

Abstract

Thermally and chemically stable spinel ferrites are electrically nonconductive material. These are important for their magnetic and dielectric properties. Spinel thin films of magnesium aluminium oxide are prepared on copper substrate using electrodeposition technique. A series of seven samples are prepared by changing the deposition time from 30 min to 120 min with an interval of 15min. In-situ oxidation is carried out for each sample for a fixed time of 10 min. Thin films are magnetic field (MF) annealed at 300 °C with an externally applied magnetic field of 500 Oe. Structural, magnetic and dielectric properties of magnesium aluminium oxide thin films are investigated by X-ray diffractometer, vibrating sample magnetometer and impedance analyzer. X-ray diffraction reveals the formation of pure phase of spinel magnesium aluminium oxide thin film at deposition time of 90 min with 10 min oxidation time. These electrodeposited magnesium aluminium oxide thin films exhibit ferromagnetism at room temperature. Pure phase exhibits maximum exchange bias of 274 Oe and minimum value of anisotropy constant (i.e. 0.121 × 109 erg/cm3). Anomalous behavior of dielectric constant is observed for the magnesium aluminum oxide thin films prepared under all conditions. Pure phase of spinel thin films prepared with 90 min deposition time exhibit higher value of dielectric constant (45.24 at log f = 5) and lower value of tangent loss (0.01 at log f = 5). Magnetodielectric coupling (MDC) is observed for electrodeposited magnesium aluminum oxide thin films suggesting its potential application in memory devices.