Magneto-resistive coefficient enhancement observed around Verwey-like transition on spinel ferrites XFe2O4 (X = Mn, Zn)

Manganese and Zinc ferrites were prepared by solid state reaction. The resulting powders were pressed into pellets and heat treated at 1100 ⁰C. The samples were characterized by using X-ray diffraction, pure phases of zinc ferrite (ZnFe²O₄) and manganese ferrite (MnFe₂O₄) were obtained. Scanning electron microscopy images showed a good contact between particles. A drop of electrical resistance was found in both samples, MnFe₂O₄ and ZnFe₂O₄, with values going from 2750 to 130 Ω and from 1100 to 55 Ω, respectively. Transition temperatures were determined to be Tv = 225 K for MnFe₂O₄ and Tv = 130 K for ZnFe₂O₄. Magnetoresistance measurements were carried out in the temperature range where R showed the transition, defined as the Verwey-like transition temperature range, ∆Tv. No magnetoresistive effect was observed out of it. The magnetoresistive coefficient (MRC) observed at ∆Tv reached its maximum values of 1.1% for MnFe₂O₄ and 6.68% for ZnFe₂O₄. The differences between MRC values are related to the divalent metal element used. Finally, the magnetoresistive response indicates that the electrical transition observed is strongly influencing the magnetoresistance; where the underlying responsible for this behavior could be a charge reordering occurring at the Verwey-like transition temperature