Magnetic permeability stability of composite material with nominal composition Ni_0.6Fe_2.4O₄

A composite material with a nominal composition of Ni_0.6Fe_2.4O₄ was prepared by the solid-phase reaction method. X-ray diffraction analysis shows that the product is composed of α-Fe₂O₃ and a solid solution of Fe₃O₄ and NiFe₂O₄. Although α-Fe₂O₃ non-magnetic phase reduces the saturation magnetization, it greatly improves the temperature and frequency stability of magnetic permeability. Based on the measurement results of the amplitude permeability in the range of −60 °C to 100 °C, the temperature coefficient α_μ and specific temperature coefficient β were calculated. α_μ and β of the composite material are 7.15 ×10^-5/^°C and 8.6 ×10^-6/^°C, respectively, which are much smaller than α_μ (1.26×10^-3/^°C) and β (9.5×10^-5/^°C) of NiFe₂O₄. At the same time, the magnetic spectrum curves show that the real part of the complex permeability μ' basically remains unchanged within the measurement frequency range (f < 10⁶ Hz). This improvement in temperature and frequency stability is attributed to the effect of the α-Fe₂O₃ phase.