Electrical and Magnetic Properties of Mg-Cr and Co-Cr Nano Ferrites Synthesized by Citrate-Gel Method

The work deals with the study of electrical and magnetic properties of Magnesium-Chromium and Cobalt-Chromium nanoFerrites for their potential applications synthesized by Citrate-Gel auto-combustion method. Structural Characterization of prepared nanoferrites was performed using XRD, SEM, EDS and TEM. XRD patterns confirmed the formation of homogeneous single phased cubic spinel belonging to the space group Fd3m (in agreement with ICSD Ref. data). It is found that crystallite size of Mg-Cr ferrites was in the range of 7-23nm and that of Co-Cr nanoferrites in the range of 6-12 nm. Structural morphology of both the ferrites was studied by SEM (Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy). Elemental compositional analysis was carried out by EDS.Electrical properties such as D.C. resistivity of prepared Mg-Cr and Co-Cr nanoferrites were studied by two probe method. The dielectric measurements as a function of frequency at room temperature were performed in the frequency range of 20Hz to 2MHz using LCR meter. Various dielectric parameters like dielectric constant (ε′), dielectric loss (ε′′) and dielectric loss tangent (tan δ) were measured as a function of frequency. The magnetization measurements of the prepared nanoferrite samples were carried out at room temperature in the applied field of ±15KOe using Vibrating Sample Magnetometer (VSM). From the obtained M-H loops, various magnetic parameters such as Saturation Magnetization (Ms), Coercivity (Hc) and Remanence Magnetization (Mr) were measured. Magnetization as a function of field (±10T) at 5K, 25K, 300K temperatures was measured using VSM. Super-paramagnetic nature of some specified samples in Mg-Cr nanoferrites system was investigated from the temperature dependence of both the field cooled (FC) and the zero-field cooled (ZFC) magnetization measurements under a field of 100 Oe in the temperature range 5K to 350K.From the results of D.C. resistivity measurements it is observed that the resistivity decreases with increase in temperature for both Mg-Cr and Co-Cr nanoferrites suggesting the semiconducting behavior of the samples. Dielectric measurements suggest that the conduction in the ferrite systems may be due to the polaron hopping mechanism. The low loss tangent values at high frequency show the potential applications of these materials in high frequency microwave devices. Mg-Cr nanoferrites were synthesized yielding narrow hysteresis loops which are the characteristic of very soft magnetic materials that are desirable for their utility in Transformers, Inductor cores, Microwave devices and Magnetic shielding. Hysteresis loops of Co-Cr nanoferrites show the medium hard magnetic behavior of the materials. MgFe2O4 shows superparamagnetic behavior above room temperature and MgCr0.9Fe1.1O4 shows superparamagnetic behavior with the blocking temperature 94.5K. Hence these nanoferrites find applications in targeted drug delivery and in Magnetic Resonance Imaging (MRI) in biomedical field. The observed results can be explained in detail on the basis of composition and crystallite size.Contents of Paper