Effects of nitriding temperature on the structure and magnetic properties of CoFe2 alloy
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It has been reported that the nitridation can increase the magnetization of α-Fe by 20%. The CoFe2 alloy has the highest magnetization among all binary alloys, thus whether the nitridation can further enhance its magnetization. In the present work, the uniform and dispersed 16-nm CoFe2O4 particles were separated by the MgO matrix in order to prepare the fine CoFe2 particles, beneficial for the nitridation reaction. With increasing the nitridation temperature, the crystal structure of the Co–Fe–N alloy experiences α″-Fe16N2 below 250 °C, γ′-Fe4N at 300 °C and ε-Fe3N between 350 °C and 500 °C. The single-phase ε-CoFe2N was synthesized at 400 °C, a much lower temperature than that previously reported. The results of magnetic measurement at 10 K show that the nitridation at 200 °C increases the magnetization of CoFe2 from 228 to 292 emu/g by 28%; the nitridation at temperatures of 200, 250 and 300 °C enhances both the magnetization and coercivity of the CoFe2 alloy. These CoFe2 nitrides are very interesting and of importance both from physical and industrial aspects, which deserves further investigations.
This work was supported by the National Natural Science Foundation of China (Grant nos. 51471001 and 11174004).
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