Chemical synthesis of Mn-Zn magnetic ferrite nanoparticles: Effect of secondary phase on extrinsic magnetic properties of Mn-Zn ferrite nanoparticles

This paper presents a comprehensive investigation of the magnetic properties of co-precipitated MnxZn(1-x)Fe(2)O(4) nanoferrites, where x takes the values of 0.5, 0.6, and 0.7. X-ray diffraction patterns indicated the presence of spinel phase. However, the ferrite composition x = 0.6 contains little trace of secondary phase alpha-Fe2O3. The occurrence of cation redistribution in the current ferrite samples can be concluded from the deviation of oxygen position parameter (U) to that of optimum value (0.375). The bond angles facilitate the reduction of the A-B interaction and the increase of the B-B interaction. With the substitution of Mn2+ ions, the saturation magnetization (M-s) exhibits both drops and increases whereas the coercivity (Hc) consistently declines. The ferrite composition x = 0.7 exhibits the maximum value of M-s and is equal to 27.9 emu/g. The blocking temperature (T-B) rises in proportion to the degree of Mn2+ ion doping. The observation of quadruple doublets in the Mossbauer spectra indicates that the ferrite nanoparticles exist in single domain state exhibiting the quadruple interactions. The range of isomer shift (delta) 0.199-0.267 mm/s indicates the existence of exclusively high spin Fe3+ ions. Two paramagnetic doublets are anticipated to exist as a result of the core and shell of present ferrite nanoparticles. In the core-shell morphology of nanoparticles, the core is characterized by larger quadruple splitting (Delta) while the shell is characterized by smaller Delta. The results are integrated in terms of magneto-crystalline anisotropy and secondary phase presuming the core-shell structure of nanoparticles.