Structures and magnetic properties of Fe-N alloys formed by ball milling of mixture of Fe and BN

摘要

Diffusion reaction between Fe and BN and structural and magnetic properties of Fe-N alloys are investigated by ball milling of mixture of the α-Fe and hexagonal BN powders with volume ratio of 1:12.5, 1:5.4, 1:1.2 and 1:0.38 up to 72 h. It is found that Fe can react with N of the BN to form amorphous Fe-N alloy (α-Fe-N) when the grain size of the Fe decreases to 8 nm and the hexagonal BN transforms into amorphous BN; further milling, α-Fe-N can crystallize to ε-Fe_xN. The formation of ε-Fe_xN is related to the volume ratio of Fe to BN, when the ratio is larger than 1:0.38, no ε-Fe_xN forms. The N content of ε-Fe_xN increases with milling time and the volume ratio increased, resulting in decrease in saturation magnetization of ε-Fe_xN. ε-Fe xN transforms from ferromagnetism to paramagnetism, when the N content exceeds 43 at%.