Enhancement of magnetic properties by Co substitution in Nd3(Fe1-xCox)27.5Ti1.5 (x=0, 0.1, 0.2, 0.3, 0.4) intermetallic compounds

A novel series of rare earth - transition metal 3:29-type intermetallic compounds has been synthesised, with nominal stoichiometry Nd-3(Fe1-xCox)(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 alpha-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 xgreater than or equal to 0.2 and at room temperature the compounds present an easy-magnetisation direction along the [4 0 -2] direction.