Dy^3＋-doped ferrite nanocrystals were prepared by a chemical co-precipitation method and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Gouy magnetic balance, vibrating sample magnetometer (VSM), and X-ray energy spectrum (EDX), respectively. The effects of dysprosium contents on structure, magnetic properties and size of the ferrite were investigated. The results show that Dy^3＋can enhance the magnetic properties which are strongest while n(Fe^3＋)∶n(Dy^3＋) is 14∶1 among the samples prepared, and weaken the coercive force of the spinel ferrite. Dy^3＋ fills in the spinel ferrite lattice and mostly enters B site. The size of the Dy-doped ferrite nanoparticles becomes smaller and their distribution is more concentrated and uniform. The average diameter of the ferrite nanoparticles is 14 nm before doping and reduces to 8 nm after doping when n(Fe^3＋)∶n(Dy^3＋) is 14∶1. The results support the concept that the soft magnetic ferrite nanocrystals with superparamagnetism can be applied to nanometer magnetic fluid field.

Key words: spinel, ferrite, dysprosium, doping, magnetic property