High coercivity in Fe-Nb-B-Dy bulk nanocrystalline magnets

The paper refers to structural and magnetic properties of the (Fe80Nb6B14)(1-x)Dy-x (x = 0.08, 0.10, 0.12, 0.16) bulk nano-crystalline alloys prepared by making use of the vacuum suction casting technique. The samples are in a form of rods with different diameters d = 1.5, 1, and 0.5 mm. The phase structure was investigated by XRD technique and reveals an occurrence of magnetically hard Dy2Fe14B as well as other relatively soft Dy-Fe, Fe-B, and Fe phases dependently on the Dy content. The alloys show hard magnetic properties with high coercive field up to 5.5 T (for x = 0.12 and d = 0.5 mm). The observed magnetic hardening effect with the increase of cooling rate (decrease of sample diameter d) can be attributed to a formation of ultra-hard magnetic objects as well as increasing role of low dimensional microstructure. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim