Structural correlation and tunability of magnetic and electric properties of manganese doped cobalt ferrite nanoparticles

Abstract

In the present work, three systems of manganese (Mn) doped cobalt ferrite nanoparticles were synthesized by the planetary ball milling technique with the composition formula Co1+xMnxFe2-xO4,Co1-xMnxFe2O4 and CoMnxFe2-xO4,where 0.125≤x≤0.5 in step 0.125. The synthesized sampleswere characterized by their structural, electrical, and magnetic properties. The crystallinity and single-phase cubic spinel structure at thecalcinationtemperature 9000Careconfirmed by their XRD patterns.The decreasing trend in their lattice constant may be attributed to the relatively smaller ionic size of dopant (Mn). The enlarged crystallite size is observed Co1+xMnxFe2-xO4 due to elevated calcination temperature.The Field Emission Scanning Electron Microscopic images show agglomerated particles with average particles sizes in the nanoscaled range. The frequency responseof ’of all three systems' demonstrates the ferrimagnetic behavior at room temperature. The appearance of peaks in the”(f)spectra of Co1+xMnxFe2-xO4 showthe grain boundary contribution to their resistivity that causes the thermal energy dissipation. This behavior of” may make the sample suitable for use in hyperthermia or related research in medical science. The increasing trend of the activation energy, EainCoMnxFe2-xO4with Mn content implies a spin disorder phenomena leading to a possible ferrimagnetic-to-paramagnetic phase transition and thus tune the material to behave as a soft magnetic material above the room temperature. The temperature dependence of dc resistivity, of Co1+xMnxFe2-xO4systemexhibits the semiconducting behavior above the room temperature that make them suitable for the possible applications in thermoelectric devices. A characteristic temperature,Tcharis marked at around 162Kin Co1+xMnxFe2-xO4systemthat sets a boundary between long-range mobility and short-range mobility of charge carriers/ions.A crossover frequency is noticed at around 58kHzin the spectra of magnetic modulusofCo1+xMnxFe2-xO4. Above this crossover frequency, magnetic modulus is correlated to the crystallite/grain size. The Nyquistplot of the electric modulus separates the contribution of n-type and p-type ions in the conductivity ofCo1-xMnxFe2O4. Comparatively, an enhanced ac permeability is observed in Co1-xMnxFe2O4 that make this system suitable to be used in high frequency applications.A phase transition between ferromagnetic to spin-glass state is observed in Co1+xMnxFe2-xO4 and CoMnxFe2-xO4 systems in the low temperature regime.