Sub-ambient magnetic properties of nanophase Nd/Pr–Fe–B based hard magnetic alloys

The magnetic characteristics of nanocrystalline Nd/Pr–Fe–B based alloys at sub-ambient temperatures have been investigated. The increasing degree of exchange coupling between the RE2Fe14B nano-grains with decreasing mean diameter dg leads to a progressive decrease in the spin reorientation temperature TSR. Co substitution for Fe slightly decreases TSR. Increasing Pr substitution for Nd decreases TSR linearly but a spin reorientation still occurred up to at least 75% Pr substitution. The effects of composition on the low temperature magnetic properties for (Nd/Pr)–(Fe/Co)–B alloys result not only from the changes in saturation magnetization and anisotropy field but also from the spin reorientation. However, the present results show that the spin reorientation does not degrade the low temperature magnetic properties for (Nd/Pr)FeB based alloys. Both the single phase nanocrystalline (Nd/Pr)FeB alloys and the nanocomposite (Nd/Pr)FeB alloys with small to medium volume fractions of α-Fe phase have very good properties and can be considered as ideal magnets for low temperature applications.