Effects of Ni2+ concentration on the composition, structure, magnetic properties, and DC-bias superposition characteristics of NiCuZn ferrites

Ni x Cu 0.2 Zn y Fe 1.98 O 4 ( x  = 0.16, 0.26, 0.35, 0.43, 0.50; y  = 0.8− x ) ferrites were prepared via solid-state reaction. The influence of Ni 2+ concentration on ferrites composition, microstructure, magnetic properties and DC-bias superposition characteristics was studied by XRD , SEM, XPS , and VSM. Then, the effect of magnetic properties on the DC-bias superposition characteristics was analyzed. The results showed that the ferrites sintered at 900 °C for 3 h were all in pure spinel phase with an average grain size of 7.5 μm and a relative density of about 5.15 g cm −3 . With the increase in Ni 2+ concentration, the saturation magnetization ( M s ) and coercivity ( H c ) of ferrites increased, but the magnetocrystalline anisotropy constant ( K 1 ) first increased and then decreased. And the M s , H c , and K 1 of the specimen with x  = 0.43 were 63.62 emu·g −1 , 27.36 Oe, and 1813.17 Oe·emu·g −1 , respectively. In particular, the specimen of x  = 0.50 achieved the best DC superposition characteristics, where the H 70% was about 220 A m −1 . The incremental permeability of the specimens decreased rapidly at a bias magnetic field <400 A m −1 . The variation mainly originated from the domain wall displacement, and the rate of decrease was influenced by both M s and K 1 . At a bias magnetic field ≥400 A m −1 , the incremental permeability of the specimens decreased slowly, mainly because the number of domain walls decreased until disappearing, and the specimens tended to become a single domain structure. And the rate of decrease of incremental permeability was mainly affected by K 1 .