Structural and magnetic properties of Nd3(Fe1-xCox)(27.7)Ti-1.3 (0 < x <= 0.4) alloys

Structural and magnetic properties of a novel series of intermetallic compo unds, with nominal stoichiometry Nd-3(Fe1-xCox)(27.7)Ti-1.3 (0 < x less tha n or equal to 0.4) are presented. The samples crystallise in the Nd-3(Fe,Ti )(29)-type structure with monoclinic symmetry (space group A2/m). The unit cell volume is decreasing as the Co content increases; the cell parameters show anisotropic decrease with the Co content. The Curie temperature increa ses monotonically with x from 437 to 878 K and the room temperature saturat ion magnetisation increases from 143.3 for x = 0 to 172.5 Am-2/kg for x = 0 .3 and remains practically the same for x = 0.4. For x = 0 and 0.1 a tilted magnetic structure is observed. For x greater than or equal to 0.2 the com pounds present an easy-magnetisation direction along the [4 0-2] direction. Ac susceptibility curves in the whole range of the Co content (x = 0-0.4) reveal a broad transition at about 160 K, whereas for x = 0-0.2 a sharp one with the corresponding transition temperature decreasing with increasing C o content. The observed changes of the critical temperatures observed in th e ac susceptibility curves and the obtained anisotropy field values are rel ated to the change of the magnetic anisotropy at x = 0.2. The average hyper fine field values depend on the Co content in a way similar to the dependen ce of the saturation magnetisation. (C) 2001 Elsevier Science BN. All right s reserved.