Magnetic properties of Ni-Cu-Zn ferrite nanoparticles at cryogenic temperature probed under Mössbauer and VSM studies

Abstract

This article presents a comprehensive analysis of magnetic properties of Ni_xCu_0.1Zn_0.9−xFe₂O₄ (x = 0.5, 0.6, 0.7). Typical variation of bond angles supported the A-B superexchange interaction. The unsaturated magnetization even at higher applied field shows the core–shell interactions of present ferrite nanoparticles. Neel’s sublattice and core–shell models have been adopted to analyze the magnetic behaviour. The saturation magnetization is unevenly varying in both sintered ferrite samples. It was found to be in the range of 15.29–28.04 emu/g. The highest of saturation magnetization (28.04 emu/g) was reported for the ferrite composition Ni_0.7Cu_0.1Zn_0.4Fe₂O₄ sintered at 500 °C. The coercivity seems to be dependent on magnetic anisotropy. The cusp between the field cooled and zero field cooled curves revealed the large distribution of ferrite nanoparticles in different sizes. The blocking temperature increases in both sintered ferrite samples with the substitution of Ni²⁺. The blocking temperature depends on the variation of crystallite size. The appearance of quadruple and hyperfine spectral lines in Mössbauer spectra represent the distribution of ferrite nanoparticles in different sizes. The range of isomer shift (0.194 – 0.463 mm/s) is less than 0.5 mm/s that represents the presence of only high spin Fe³⁺ ions.