ENHANCEMENT OF MAGNETIC PROPERTIES BY Co SUBSTITUTION IN Nd_3(Fe_(1-x)Co_x)_(27.5)(x= 0, 0.1, 0.2,0.3,0.4) INTERMETALLIC COMPOUNDS

摘要

A novel series of rare earth - transition metal 3:29-type intermetallic compounds has been synthesised, with nominal stoichiometry Nd_3(Fe_(1-x)Co_x)_(27.5)Ti_(1.5) (x= 0, 0.1,0.2, 0.3, 0.4), extending the solubility limit of Co atoms in the Fe sites up to 0.4. The Nd_3(Fe,Ti)_(29)-type structure with monoclinic symmetry (space group A2/m) is dominant in all samples, with some Nd(Fe,Co,Ti)_(12) as a secondary phase and a small amount of α-Fe(Co). The unit cell volume is decreasing anisotropically as the Co content increases. The Curie temperature increases monotonically with x, from 437 to 876 K for the 3:29 phase, and from 553 to 918 K for the 1:12 secondary phase. The saturation magnetisation increases with x from 143.3 to 175.5 Am~2/kg and the anisotropy field increases from 3.7 T to 5.2 T. For x≥0.2 and at room temperature the compounds present an easy-magnetisation direction along the direction.