The influence of annealing parameters (time $t_a,$ current $I_a,$ and applied stress ${\sigma }_a)$ on magnetic properties of Joule heated amorphous ${\mathrm{Co}}_{\mathrm{68.15}}{\mathrm{Fe}}_{\mathrm{4.35}}{\mathrm{Si}}_{\mathrm{12.5}}{\mathrm{B}}_{\mathrm{15}}$ glass covered microwire (13 μm) was investigated. Annealing under applied stress induces additional anisotropy which is proportional to ${\sigma }_a$ and can be removed by subsequent heating without stress. The magnetoimpedance, measured on the sample with the lowest anisotropy field ${\mathrm{(H}}_K\text{≈120\hspace{0.5em}}{\mathrm{Am}}^{\mathrm{-1}}\mathrm{),}$ shows sharp maxima at ${\mathrm{H=\pm H}}_K.$ For driving currents higher than 0.2 mA nonlinear behavior is observed, and the magnitude of giant magnetoimpedance significantly decreases. The maximum relative change of impedance (60%), observed for the highest frequency, 900 kHz, compares well with the values reported on conventional wires.

Effect of Ni addition on structural properties and, cation distribution of Zn 0.75-x Ni x Mg 0.15 Cu 0.1 Fe 2 O 4 (x = 0.0, 0.15, 0.30, 0.60, 0.75) ferrites, prepared using sol-gel autocombustion method was studied using X-ray diffraction (XRD) technique. XRD analysis reveals the formation of spinel phase even in dry gel form. The lattice constant (a exp.) decreases with Ni 2+ substitution and follows Vegard's law. Scherrer's grain diameter (D) lies within the range of 17.33-26.47 nm. Due to difference in the ionic radii of Zn 2+ and Ni 2+ significant changes are observed in the structural parameters-unit cell volume (V), hopping length at A (L A) and B (L B) site, and x-ray density (ρ XRD). Linear increase in Neel magnetic moment (n B N) with oxygen positional parameter is observed in the studied samples, attributed to simultaneous weakening of A-B interaction and strengthening of the B-B interaction.

We report the role played by cation distribution in determining magnetic properties by comparing dry gel, thermally annealed Ni ferrite prepared by sol-gel auto-combustion technique. X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Mössbauer spectroscopy were used to characterize the samples. Both XRD and Mössbauer measurements validate the formation of spinel phase with grain diameter 39.13−45.53 nm. First time antistructural modeling for Ni ferrite is reported to get information on active surface centers. Decrease of Debye temperature θ_D in annealed sample shows enhancement of lattice vibrations. With thermal annealing experimental and Néel magnetic moment (n_B^e, n_B^N) increases, suggesting migration of Ni²⁺ from B to A site with concurrent migration of Fe³⁺ from A to B site (non-equilibrium cationic distribution), affecting magnetic properties.