Si doping magnetite particles were synthesized by hydrothermal using of silane coupling agents. According to increase the amount of the silane coupling agent, the crystallite diameter of the magnetite particles was reduced. The saturation magnetizations tend to decrease gradually with an increase in the content of Si, and the coercivity was rapidly decreased. According to increasing the amount of the silane coupling agents, the dispersibility of the particles by working silicon and carbon functionalities was improved. These magnetite particles were reduced by H2 gas and nitrided by NH3 gas. In the case of the using the pure magnetite, it was not only synthesized with α-Fe. In the case of the magnetite doped with the silicon content of 1.6 mol％ and 2.7mol％, α"-Fe16N2 could be synthesized. Furthermore the case of silicon addition 4.2 mol％, α-Fe particles kept and the coercivity was decreased.
