Study of NiCuZn ferrite powders and films prepared by sol–gel method

This paper reports that a series of NiCuZn ferrite powders and films are prepared by using sol–gel method. The effects of raw material composition and the calcinate temperature on magnetic properties of them are investigated. The NiCuZn ferrite powders are prepared by the self-propagating high-temperature synthesis method and subsequently heated at 700℃ ～1000℃. The results show that NiCuZn ferrite powders with single spinel phase can be formed after heat-treating at 750℃. Powders obtained from Ni_0.4Cu_0.2Zn_0.4Fe_1.9O₄ gel have better magnetic properties than those from gels with other composition. After heat-treating at 900℃ for 3 h, coercivity H_c and saturation magnetization M_s are 9.7 Oe (1 Oe = 80 A/m) and 72.4 emu/g, respectively. Different from the powders, NiCuZn films produced on Si (100) from the Ni_0.4Cu_0.2Zn_0.4Fe₂O₄ gel formed at room temperature possess high properties. When heat-treating condition is around 600℃ for 6 min, samples with low H_c and high M_s will be obtained. The minimal H_c is 16.7 Oe and M_s is about 300 emu/cm³. In comparison with the films prepared through long-time heat treating, the films prepared through short heat-treating time exhibits better soft magnetic properties.