Intrinsic magnetic, structural and resistivity properties of ferromagnetic Mn0.5Zn0.5AlxFe2−xO4 nanoparticles

In this work the nano-structural, magnetic and resistivity properties of Al3+ substituted Mn–Zn ferrites powders were investigated. Mn0.5Zn0.5AlxFe2−xO4 powders, where x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 were obtained by the sol–gel auto-combustion method. X-ray diffraction data indicate that, after substitution, all the samples consisted of the main spinel phase in combination with a small amount of a foreign Al2O3 phase. The addition of Al3+ resulted in a reduction of particle size and density of the prepared samples. Cation distribution in the present study was estimated by using X-ray diffraction data. The tetrahedral site radii initially increased with Al3+ content while the octahedral site radii decreased with the Al3+ substitution. FTIR spectra show two strong absorption bands at 529–548 cm−1 and 445–452 cm−1 which are the typical bands for the cubic spinel crystal structure. The magnetic properties were measured by employing a vibrating sample magnetometer. It was observed that the saturation magnetization, coercivity and anisotropy field decreased with the increase of Al3+ substitution. Introduction of Al3+ ions into the Mn–Zn ferrite increased the values of the resistivity, especially in the lower temperature range.