Curie temperature enhancement of Nd2Fe14B in nanocomposite exchange-spring alloys

Curie temperatures were measured on a series of four melt-spun nanocomposite materials comprised of Nd2Fe14B and varying amounts of excess iron ranging from ∝0 to 27 wt%. The phase constitution and grain size were assessed with synchrotron X-ray diffraction; the Curie temperatures were measured by differential thermal analysis and DC SQUID magnetometry in the temperature range 375 K≤T≤800 K. The Curie temperature of the 2-14-1 phase increases with increasing excess iron; thermal measurements indicate a 13 enhancement over that of pure Nd2Fe14B for 27 wt% α-Fe, while the magnetic measurements indicate a 18 enhancement for the same composition. The results are consistent with the theoretical predictions of Wang and Mills for analogously modeled materials. (orig.)