| Ni0.7Zn0.3Fe2+xO4 (x= -0.3～0.3) and CoxNi0.7-xFe2O4 (x= 0.0～0.4) nanoparticles are fabricated by sol-gel combustion method, in order to study the effect of Fe and Co ion substituted on the structure and magnetic properties in nanosized Ni-Zn ferrite. IR, DTA, TEM, XRD and VSM were used to study the properties of the sample.The thermal decomposition temperature of dried gel is about 210℃, and Ni-Zn ferrite nanoparticles could be synthesized in the self-propagating combustion process. The organic matter such as C has been burnt out and the particles grown up after the sample is annealed at high temperature. For Ni0.7Zn0.3Fe2+xO4 sample,the particles are spherical and uniform, the size is between 44～73 nm,and the configuration of particle is not effected obviously by the content of Fe. The main phase is the spinel structure ferrite,the second phaseα-Fe2O3 appears in the samples when x>0;the second phase NiδZn1-δO appears when x<0. And the content of the second phase increased with the increasing of the absolute value of x. The saturation magnetization (MS) is increased nonlinearly with increasing x. But Ms of the non-stoichiometric sample is smaller than 75 emu/g of Ni0.7Zn0.3Fe2O4. The coercivities (Hc) is between 50～87 Oe.CoxNi0.7-xFe2O4 sample annealed at 600℃and 700℃is spinel phase. The particle size is between 40 and 55 nm,and is increased with the enhance of the annealing temperature and the increase of the content of Co. The lattice constant a increased with increasing x. The peak corresponding to ferrite in IR spectrum appeared red shift with the decrease of the particle size。All samples show ferromagnetism, and the Ms increased with the increasing of x and annealling temperature. The Hc increased with the increasing of x and the decreasing of the annealling temperature.
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