Elevated temperature magnetic properties and micromagnetic analysis in Nd-Fe-B based hard-magnetic nanocomposites

Effects of partial substitution of nonmagnetic Sn for Fe on elevated temperature magnetic properties in exchange-coupled Nd2Fe14B/(Fe3B, α-Fe) nanocomposites have been investigated. Thermal stability of remanent magnetization (Jr) and coercivity (Hc) is found to increase on Sn substitution. The absolute values of the temperature coefficients α(Jr) and β(Hc) decrease from 0.098 and 0.323 to 0.061 and 0.288, respectively with increase in Sn content from 0 to 1.5 at%. Influence of non-ideal microstructure and exchange coupling on the coercivity has been studied by analyzing the microstructural parameters αKαex and Neff determined from the temperature dependence of the coercivity. Substitution of Sn significantly decreases the value of Neff from 0.042 to 0.005 indicating a decrease in the local stray fields at the grain boundary.