Low temperature ferromagnetic behavior and temperature dependent anomalous dielectric relaxation of Zn_0.90Ni_0.05Mn_0.05O diluted magnetic semiconductor

We report structural, magnetic and temperature dependent dielectric properties of diluted magnetic semiconductor Zn_0.90Ni_0.05Mn_0.05O prepared by solid state reaction technique. X-ray diffraction analysis revealed formation of single phase hexagonal wurtzite structure. Scanning electron microscopy and atomic force microscopy images indicated increase in grain size and roughness respectively with increasing sintering temperature. Field dependent DC magnetization at low temperature exhibited ferromagnetic ordering with coercivity ~ 6 × 10⁴ A/m and remanence ~ 17 A/m. Complex initial permeability values were found to be positive for the measurement frequency range (1 kHz–120 MHz) with a relaxation at lower frequency. Temperature dependent DC magnetization and AC susceptibility followed curie law with curie temperature below 65 K. Temperature dependent dielectric constants (\(\varepsilon ^{\prime}\,\& \,\varepsilon ^{\prime\prime}\)) and loss tangents (\(tan\delta\)) measured for selected frequencies were found to be an increasing function of temperature and decreasing function of frequency. AC conductivity (\({\sigma }_{ac}\)) values were found to be an increasing function of frequency and temperature. Clear signatures of relaxations were observed in \(\varepsilon ^{\prime},\,\varepsilon ^{\prime\prime},\) \(tan\delta\) and \({\sigma }_{ac}\) for temperatures above 200 °C.