Electrical and magnetic transport properties of Ni–Cu–Mg ferrite nanoparticles prepared by sol–gel method Khalid Mujasam Batoo a,⇑ , M.-S. Abd El-sadek b a King Abdullah Institute for Nanotechnology, King Saud University, P.O. Box 2460, Riyadh 1151, Saudi Arabia b Nanomaterial Laboratory, Physics Department, Faculty of Science, South Valley University, 83523 Qena, Egypt article info Article history: Received 8 May 2012 Received in revised form 21 February 2013 Accepted 22 February 2013 Available online 7 March 2013 Keywords: Nanoparticles Ferrites Transmission electron microscopy Dielectric constant ac Conductivity dc Magnetization abstract Nanoscale Ni 0.7x Mg x Cu 0.3 Fe 2 O 4 (0.0 6 x 6 0.5) ferrite powders were prepared by sol–gel method and obtained as dried gel after successful reaction between respective metal nitrates. X-ray diffraction (XRD) confirmed the successful synthesis of materials, and the formation of single-phase cubic spinel structure. The average particle sizes of these materials were found between 40 to 50 nm and confirmed by TEM (±1). Dielectric constant (e 0 ) measured in the frequency range (42 Hz to 5 MHz) was found to decrease with increasing frequency of the applied field, which shows normal behavior, and has been explained in the light of Maxwell–Wagner interfacial polarization. Debye relaxation peaks were observed for lower concentration of Mg in frequency dependent dielectric loss tangent curves. Real and imaginary parts of impedance (Z 0 and Z 00 ) suggest existence of one relaxation mechanism which is attributed to the co-effect of grains and grain boundaries. The room temperature dc magnetization studies infer magnetic moment of Ni–Cu–Mg nanoparticles decreases with increasing Mg 2+ doping content. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction The field of spinel ferrites is well established because of their various potential applications. Even after more than half of the cen- tury, the scientists, researchers, technologist, and engineers are still excited in various types of bulk as well as nanoscale ferrite materials. The properties of ferrites can be modified by substitu- tions [1,2] or additions [3], and also by controlling the sintering temperature and time. The recent trend is focused on doped ferrite materials prepared through various synthesization techniques with different cation concentrations that in turn affect the various properties such as electrical, dielectric, and magnetic. Multilayer chip inductors (MLCIs) [4] are one of the important components for latest electronic products used in cellular phones, video cameras, note book computers, etc., because they are fabri- cated by putting alternate layers of ferrite and silver electrodes [4]. The magnetic and electrical properties of soft ferrites can be easily tuned by incorporation of suitable dopant elements (divalent or trivalent cations) in a spinel structure. Therefore, spinel ferrites have become an important class of commercially available materi- als extensively used in microwave and electrical industries [5], such as pulsed transformers, inductors, reflection coils, antennas and modulators because of their high resistivity combined with useful ferromagnetic as well as dielectric properties [4]. It is well established that the structural, dielectric and magnetic properties of ferrites are strongly dependent on the method of preparation, sintering temperature, chemical composition and par- ticle size [6]. Hence, the study of such properties at different fre- quencies, chemical compositions and temperatures may provide valuable information about the kind and amount of additives re- quired to obtain high quality materials for practical applications. As a result, the study of electric and dielectric properties is equally important as those of magnetic properties from the applied funda- mental research point of view. Many efforts [7–12] have been made to improve the basic properties of ferrite materials by substi- tution or by adding various ions of different valence states, depending on the applications of interest. Generally, substitutions of divalent or trivalent ions in pure ferrites results in the modifica- tion of their structural, electrical and magnetic properties. What makes investigation of ferrite nanoparticles such as Ni–Cu– Zn or Ni–Cu noteworthy is the difference in cation distributions and spin structure of A and B sites. Li et al. [13] studied the structure and applied field Mössbauer properties of NiCuZn ferrites. They found the hyperfine field of A site increased from Hhf(A) from 507 to 521 kOe, while the average value of B site decreased from Hhf(B) from 522 to 447 kOe at 4.2 K. Geisari et al. [14] observed the satura- tion magnetization in NiZn ferrite nanocrystalline powder increased significantly from 17.92 emu/g to 77.04 emu/g with increasing tem- perature from 300 °C to 750 °C. Khan et al. [15] reported that the complex permeability of the Fe-deficient NiCuZn can result in an in- crease in complex initial permeability, increase in Curie tempera- 0925-8388/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jallcom.2013.02.129 ⇑ Corresponding author. Tel.: +966 562783779; fax: +966 14670662. E-mail addresses: khalid.mujasam@gmail.com, kbatoo@ksu.edu.sa (K.M. Batoo). Journal of Alloys and Compounds 566 (2013) 112–119 Contents lists available at SciVerse ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom