Study of spinel ferrites with addition of small amount of metallic elements Hafiz Muhammad Tahir Farid 1 & Ishtiaq Ahmad 1 & Irshad Ali 1 & Shahid M. Ramay 2 & Asif Mahmood 3 Received: 22 April 2017 /Accepted: 20 September 2018 /Published online: 5 December 2018 # Springer Science+Business Media, LLC, part of Springer Nature 2018 Abstract Spinel ferrites MPr 0.1 Fe 1.9 O 4 (M = Mn, Cu, Mg) were prepared by sol-gel technique. X-ray Diffraction (XRD) showed that along with spinel phase, secondary phase (PrFeO 3 ) appeared for all composition. Scanning electron microscopy showed the inhomo- geneous grain size. Temperature dependence normalized AC susceptibility and Curie temperature of spinel ferrites revealed that in all the samples transitions from multi domain (MD) to single domain (SD) occurred. Magnetic properties exhibited the soft nature of all the samples at room temperature. Temperature dependent resistivity of all the samples increased as the temperature was enhanced, representing the semiconducting behavior. Dielectric constant and complex dielectric constants were determined at the high-frequency range of 1 MHz to 3 G Hz. Impedance analysis clearly demonstrated the role of grains and grain boundary in the spinel ferrites. Cole-cole plots of all the samples showed only one semi-circle at high-frequency. All the samples elaborated the good picture of Koop’ s theory and Maxwell-Wagner model. The low value of coercivity and high magnetization of Mn-based spinel ferrites made it suitable for hyperthermia applications. Keywords Spinel ferrites . Pr-Fe-O . Susceptibility . Hyperthermia . AC conductivity . Cole-Cole plots 1 Introduction Ferrites are the ferrimagnetic oxides that can be classified into several classes on the basis of their shape such as hexagonal ferrites, spinel ferrites and garnet ferrites etc. The spinel fer- rites are included in a broad family of the ferrites because of their potential applications. At microwave frequencies, the spinel ferrites are found most suitable for their uses because of high electrical resistivity and minute losses of eddy current [1]. MFe 2 O 4 is a chemical formula for the cubic spinel ferrite in which BM^ is the divalent metal ion, as for example Cu 2+ , Zn 2+ , Sr 2+ , Mg 2+ , Fe 2+ , Ni 2+ and Cd 2+ etc. [2]. For a spinel ferrite, FCC is the unit cell with eight formula units. The shape of spinel crystals is being found by the ions of oxygen or by the arrangement of anions in the lattice. Scientifically, the spinel ferrites have well-known significance in the modern society because of their hopeful magnetic properties [3]. Gilchrist et al. [4] initially exposed the treatment of cancer that is known as magnetic hyperthermia treatment. In a logical society, the nano-shaped magnetic materials are greatly used for bio-medication [5]. In case of magnetic hyperthermia, the multifunctional and super paramagnetic nano-particles are re- ceiving additional appreciation [6]. These nano-particles are being used as contrasting agents and multi-functional probes for MRI (magnetic resonance imaging), MPI (magnetic parti- cle imaging), OFI (optical fluorescence imaging), MFH (mag- netic fluid hyperthermia), MRS (magnetic resonance spectros- copy), PET (positron emission tomography) and USI (ultra- sound imaging) due to their non-toxicity, high sensitivity, high magnetic susceptibility and simplistic conjugation with bio- logical functional unit [6]. For the preparation of samples, sol- gel auto-combustion technique has been adopted. This tech- nique is best to prepare the spinel ferrites of controlled size. Mostly this technique is being used because it provides sig- nificant results. The motivation of the present study was to improve the electrical properties at high frequencies (from microwaves to radio frequencies). Polycrystalline properties of the ferrites like dielectric properties & DC electrical resis- tivity are mostly influenced by the sintering conditions, * Hafiz Muhammad Tahir Farid tahirfaridbzu@gmail.com 1 Department of Physics, Bahauddin Zakariya, University Multan, Multan 60800, Pakistan 2 College of Science, Physics and Astronomy Department, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia 3 Chemical Engineering Department, College of Engineering, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia Journal of Electroceramics (2019) 42:57–66 https://doi.org/10.1007/s10832-018-0154-x