Well-dispersed uniform hard magnetic CoFe_2O_4 nanoparticles were synthesized by thermal decomposition of a metal-organic salt.Then they were reduced in H_2 ambient at low temperature to prepare hard CoFe_2O_4/soft CoFe_2 composites in order to weaken as possibly the agglomeration.The improved magnetic performances were obtained in this work:a higher remanence to saturation magnetization ratio Mr/Msvalue of 0.64 was obtained;with increasing the reducing time the Msvalue greatly increases to 124emu·g~(-1) wi...