Influence of Gd3+ ion substitution on the MnCrFeO4 for their nanoparticle shape formation and magnetic properties

MnCrFeO4 ferrites, where Fe3+ ions stepwise replaced by Gd3+ ions with a chemical formula MnCrGdxFe1-xO4 (x = 0.0, 0.05, 0.1 and 0.15) were synthesized by employing sol-gel auto combustion method. Crystal structure, nanocrystalline nature of particles, magnetic properties and dielectric properties were investigated by energy dispersive spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) and pulse field magnetization techniques. The phase identification of the materials by XRD reveals that the materials formed in the cubic spinel phase with small amounts of GdFeO3. TEM observation shows that some of the spherical nanocrystals are transformed in needle-like shape structure upon Gd3+ substitution. Saturation magnetization and observed magnetic moment are found to increase with Gd3+ substitution for x <= 0.1, obeying Neel's two sublattice model and decreases thereafter, showing existence of non-collinear spin interaction that gives rise to the Yafet-Kittel (theta(YK)) angles. Coercivity increased with the increasing doping of Gd3+ ions in Mn-Cr ferrite. Frequency dependent dielectric constant decreased with Gd3+ ions substitution, these results were discussed in the light of Maxwell-Wagner type interfacial polarization. (C) 2015 Elsevier B.V. All rights reserved.