Vol.:(0123456789) 1 3 Journal of Materials Science: Materials in Electronics https://doi.org/10.1007/s10854-018-8831-8 Low temperature ferromagnetic behavior and temperature dependent anomalous dielectric relaxation of Zn 0.90 Ni 0.05 Mn 0.05 O diluted magnetic semiconductor Raju Ahmed 1,2  · Anwar Siddique 1  · A. S. M. Moslehuddin 2  · Z. H. Mahmood 2  · A. K. M. Akther Hossain 3 Received: 7 September 2017 / Accepted: 27 February 2018 © Springer Science+Business Media, LLC, part of Springer Nature 2018 Abstract We report structural, magnetic and temperature dependent dielectric properties of diluted magnetic semiconductor Zn 0.90 Ni 0.05 Mn 0.05 O prepared by solid state reaction technique. X-ray difraction 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 × 10 4  A/m and remanence ~ 17 A/m. Complex initial permeability val- ues 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 (   &   ) and loss tangents ( tan) measured for selected frequencies were found to be an increasing function of temperature and decreasing function of frequency. AC conductivity (  ac ) values were found to be an increasing function of frequency and temperature. Clear signatures of relaxations were observed in   ,   , tan and  ac for temperatures above 200 °C. 1 Introduction Synthesis of diluted magnetic semiconductors (DMS) exhib- iting room temperature ferromagnetic behavior has brought spintronic [1] devices in reality. DMS materials are syn- thesized by a fractional incorporating of transitional metal (TM) ions in the substitutional sites of typical binary semi- conductors (GaN, ZnO etc.) [2, 3]. Over the last two dec- ades, most interest have been focused on the development of wide bandgap oxide semiconductors based DMSs because the lattice and conductivity mismatch at the metal–semicon- ductor interfaces critically infuences the efective spin injec- tion and those mismatches are minimal for oxide DMSs [4]. Among all the candidates for DMS, ZnO has attracted much attention because of its wide band gap energy of 3.3 eV, large excitation binding energy, lower cost, high abundance and most importantly capability of exhibiting Curie tempera- ture (T c ) at or above room temperature [2]. In ZnO based DMSs, the incorporation of TM ions is the primary means of controlling magnetic properties, and may also have an immense efect on the electrical conductivity, dielectric properties or other physical properties. The origin of ferromagnetic behavior of TM doped ZnO has been studied extensively by diferent groups and contra- dictory results were obtained in many cases [5]. Among all the TMs, Mn has the fully stable polarized state because of highest possible magnetic moment and half-flled d orbital. Therefore, it has been studied most as a TM for ZnO based DMS [6]. Xu et al. [7] experimentally observed room tem- perature ferromagnetic behavior of Mn doped ZnO and explained it as a result of acceptor defect. Substitution of Mn in ZnO was claimed to be responsible for the observed ferromagnetic behavior for some researchers [2, 6, 8]. In some reports, presence of secondary phases were claimed to be responsible for the ferromagnetic behavior [2]. For Ni doped ZnO, room temperature ferromagnetic behavior was reported by many researchers [9–11]. In most of the reports, * Raju Ahmed r_a227@txstate.edu 1 Materials Science, Engineering and Commercialization Program, Texas State University, San Marcos, TX 78666, USA 2 Department of Electrical and Electronic Engineering, University of Dhaka, Dhaka 1000, Bangladesh 3 Department of Physics, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh