Structural, magnetic and electrical characterization of Cd-substituted Mg ferrites synthesized by double sintering technique R. Zahir a , F.-U.-Z Chowdhury a,n , M.M. Uddin a , M.A. Hakim b,1 a Department of Physics, Chittagong University of Engineering and Technology, Chittagong 4349, Bangladesh b Materials Science Division, Atomic Energy Center, Dhaka 1000, Bangladesh article info Article history: Received 11 December 2015 Received in revised form 4 March 2016 Accepted 4 March 2016 Available online 5 March 2016 Keywords: Ferrites X-ray diffraction Complex permeability Quality factor Electrical resistivity abstract Cd-substituted Mg ferrites with compositional formula Mg 1x Cd x Fe 2 O 4 with 0.1 rx r0.6 in the steps of 0.1 have been synthesized by double sintering ceramic technique. The X-ray diffraction analysis has revealed that the samples crystallize in a single phase cubic spinel structure. The lattice parameter has increased with increasing Cd content in conformity with Vegard's law. The study of scanning electron microscopy has revealed that Cd substitution has increased the particle size of the ferrites increases from 2.2 to 9.2 mm. Some probable interpretations based on literature have been discussed. The increase in particle size with increasing of Cd content has consequently resulted in the initial permeability. The Curie temperature has decreased linearly with increasing Cd content which pointed out the weakening of A-B exchange interaction. The spectra of quality factor have showed a steady bandwidth of 0.1–8 MHz, this finding makes the ferrite system suitable for broadband pulse transformer. The variation of electrical resistivity (DC and AC) has been explained on the basis of electron hopping between Fe 2 þ and Fe 3 þ . & 2016 Elsevier B.V. All rights reserved. 1. Introduction Ferrites are one of the most significant magnetic materials which have been extensively used in modern electronic technol- ogies. These materials possess spontaneously magnetized domains and show the phenomena of magnetic saturation and hysteresis. They have a critical temperature above which they become para- magnetic, known as Curie temperature (T c ). For these reasons, they become important due to its unique magnetic and electrical properties with chemical and thermal stabilities [1]. Soft ferrite is a pertinent magnetic material possessing high resistivity, high permeability with low loss, high T c , low cost, high mechanical hardness and environmental stability. Recently, Mg-based ferrites have attracted much attention due to its high electrical resistivity with good magnetic properties for transformers, ferro-fluids and magnetic cores [2–4]. Magnetic properties of ferrites strongly de- pend on their chemical compositions and additives or substitu- tions. The site distribution and valencies of the cations in the spinel oxides also play an important role in their structural, magnetic, electrical and chemical properties. Magnesium ferrite (MgFe 2 O 4 ) is a partially inverse cubic spinel whose degree of inversion is sensitive to the sample preparation history. On the other hand, Cd ferrite (CdFe 2 O 4 ) has a regular spinel structure where Cd 2 þ ions occupy the tetrahedral A-sites and Fe 3 þ ions occupy the octahedral B-sites. Cd-substituted mixed ferrites such as Ni–Cd [5], Cu–Cd [6] and Li–Cd [7] show canted spin arrangement on the octahedral B-sites. Therefore, it would be interesting to investigate similar effects in the Cd-substituted MgFe 2 O 4 system. The structural, magnetic and electrical properties of MgFe 2 O 4 with nonmagnetic substances such as Cd 2 þ [8], Zn 2 þ [9] Ca 2 þ [10] Ti 4 þ [11], Zr 4 þ [12] and Al 3 þ [13] have been in- vestigated by means of XRD, magnetic and electrical measure- ments. However, it is understood that the structural, electrical and magnetic properties of the Mg–Cd ferrite system to be strongly dependent on factors like sintering temperature, grain size, pre- paration methods and compositions. The influence on the grain size due to Cd substitution; the role of Cd on the initial perme- ability at different measuring temperature and usable operating bandwidth that can be revealed by Q-factor has not been reported yet for the Cd–Mg ferrite system. Therefore, in the present work, samples having general formula Mg 1 x Cd x Fe 2 O 4 with 0.1 rx r0.6, in the step of 0.1, have been prepared by double sintering ceramic technique sintered at 1150 °C for 3 h. The structural, magnetic and electrical properties as a function of frequency and amount of substitutions have been elucidated for the prepared samples. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jmmm Journal of Magnetism and Magnetic Materials http://dx.doi.org/10.1016/j.jmmm.2016.03.019 0304-8853/& 2016 Elsevier B.V. All rights reserved. n Corresponding author. E-mail address: faruque@cuet.ac.bd (F.-U. Chowdhury). 1 Present address: Department of Glass and Ceramic Engineering, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh. Journal of Magnetism and Magnetic Materials 410 (2016) 55–62