FeCl₂, Zn(NO₃)₂ and Ni(NO₃)₂ were used as raw material to prepare acicular α-FeOOH via chemical precipitation method. And then used as the intermediate, the acicular α-FeOOH was enwrapped by the citric acid complex of Ni and Zn via citric acid method. Thus the acicular nano-Ni_xZn_1－xFe₂O₄ samples were obtained after the calcinations of the enwrapped α-FeOOH at different temperatures. The phase, the lattice constant, the morphology and the particle size of the samples were characterized by using infrared spectroscopy (IR), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The magnetic properties of the samples were sdudied by vibrating sample magnetometer (VSM). The results indicated that the Ni-Zn ferrite samples obtained via chemical precipitation-citric acid method maintained the morphology of the α-FeOOH intermediate. The diameter and length of the obtained acicular nano-Ni_xZn_1－xFe₂O₄ were found to be about 40 nm and 600 nm respectively, and aspect ratio was higher than 15. The diameter of the samples increased and the aspect ratio decreased with the increasing of the calcinations temperature. With the increasing of x value, the lattice constant of the Ni_xZn_1－xFe₂O₄ samples ranged from 0.8442 (x＝0) to 0.8353 (x＝1.00), and the coercivity changed from 63.5 Oe (x＝0) to 358.7 Oe (x＝1). The saturation magnetization of the sample increased first, and then decreased. The maximum value of the saturation magnetization of the nano-Ni_xZn_1－xFe₂O₄ was up to 58.9 emu/g (x＝0.6). Compared with the amorphous nano-Ni_xZn_1－xFe₂O₄ , the anisotropism of the acicular nano-Ni_xZn_1－xFe₂O₄ by the same method was superior. Thus the acicular nano-Ni_xZn_1－xFe₂O₄ exhibited the character of hard magnetic material.

Key words: acicular, nano-Ni_xZn_1－xFe₂O₄, α-FeOOH, magnetic property