Temperature stability of magnetic permeability of NixFe3−xO4 ferrites

NixFe3−xO4 ferrites (x = 0.6, 0.7, 0.8, 0.9, 1.0) were prepared by solid-phase reaction method. Structure and morphology were characterized by X-ray diffractometer (XRD) and scanning electron microscope (SEM). Magnetic properties were measured with B-H analyzer and magnetic properties measurement system (MPMS). NixFe3−xO4 ferrites with high Ni2+ content (x = 0.7 ~ 1.0) present pure cubic spinel phase and dense microstructure. Their saturation magnetization (Ms) and initial permeability (μi) decrease with x increasing. Temperature coefficient (αμ) and specific temperature coefficient (β) were calculated based on the permeability from -60 °C to 100 °C. The results show both of αμ and β decrease with x decreasing, indicating that proper reduction of Ni2+ content and increasing Fe2+ content help to improve the temperature stability of NixFe3-xO4. This improvement in temperature stability is attributed to the influence of Fe2+ in the ferrites on the magnetocrystalline anisotropy.