Fabrication of Nd 3+ and Mn 2+ ions Co-doped Spinal Strontium Nanoferrites for High Frequency Device Applications IQBAL AHMAD, 1 SYED MUJTABA SHAH, 1,4 MUHAMMAD NAEEM ASHIQ, 2 FAISAL NAWAZ, 3 AFZAL SHAH, 1 MUHAMMAD SIDDIQ, 1 IQRA FAHIM, 1 and SAMIULLAH KHAN 1 1.—Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan. 2.—Insti- tute of Chemical Sciences, Bahauddin Zakariya University, Multan 60880, Pakistan. 3.—Department of Basic Sciences, University of Engineering and Technology, Lahore, Faisalabad Campus, Lahore, Pakistan. 4.—e-mail: smschem69@yahoo.com Microemulsion method has been used for the synthesis of high resistive spinal nanoferrites with nominal composition Sr 1x Nd x Fe 2y Mn y O 4 (0.0 £ x £ 0.1, 0.0 £ y £ 1.0) for high frequency device applications. It has been confirmed by x-ray diffraction (XRD) results that these ferrites have a cubic spinal structure with a mean crystallite size ranging from 34 mm to 47 nm. The co-substitution of Nd 3+ and Mn 2+ ions was performed, and its effect on electrical, dielectric and impedance properties was analyzed employing direct current (DC) resis- tivity measurements, dielectric measurements and electrochemical impedance spectroscopy (EIS). The DC resistivity (q) value was the highest for the com- position Sr 0.90 Nd 0.1 FeMnO 4 , but for the same composition, dielectric param- eters and alternating current (AC) conductivity showed their minimum values. In the lower frequency range, the magnitudes of dielectric parameters decrease with increasing frequency and show an almost independent fre- quency response at higher frequencies. Dielectric polarization has been em- ployed to explain these results. It was inferred from the results of EIS that the conduction process in the studied ferrite materials is predominantly governed by grain boundary volume. Key words: Spinal nanoferrites, microemulsion method, dielectric polarization, DC electrical resistivity, structural morphology, high frequency devices INTRODUCTION Versatile and unique properties of ferrite materi- als have made this field a hot and demanding topic in last few decades. 1 Ferrite materials have found a broad variety of technological applications ranging from high frequency devices to low frequency devices. Spinal ferrites have the general formula (M 1k Fe k )A(M k Fe 2k )BO 4 , where M indicates metal cations and k represents inversion parameter. In spinal ferrites, metal occupies tetrahedral [A] and octahedral [B] sites in a cubic closed-pack arrangement of oxygen ions. A ferrite system can be called purely normal, completely inverse spinel and randomly arranged for the values of k as 0, 1, and 3/2, respectively. 2 These ferrites posses unique dielectric properties that can be controlled by opti- mizing factors like the synthesis conditions, dopants (metal ions), chemical composition, sintering tem- perature and time. Research on the electrical trans- port and dielectric properties of ferrites has contributed a lot to understanding the behavior of localized electron charge carriers, which in turn is helpful to understanding the dielectric polarization mechanism. Structural and magnetic properties of the ferrite systems can be manipulated by selecting a suitable transition metal, followed by its incorpo- ration into the ferrite lattice. 3–5 (Received February 2, 2016; accepted May 11, 2016) Journal of ELECTRONIC MATERIALS DOI: 10.1007/s11664-016-4653-8 Ó 2016 The Minerals, Metals & Materials Society