Influences of Co on structural and magnetic properties of R3(Fe1−xCox)29−yMy (R = rare earth metal, M = transition metal) intermetallic compounds

The study of the effect of Co substitution on the structural and magnetic properties of R3(Fe1−xCox)29−yMy (R = Y, Nd, Tb, Dy; M = Ti, V, Cr, Mn; 0 ≤ x ≤ 1; y = 0.9–7.0) is presented. For the compounds with low Co content (0 ≤ x ≤ 0.4) the unit cell volume is decreasing as the Co content increases. 57Fe Mössbauer spectroscopy has shown that the Co atoms avoid the dumb-bell sites. The Curie temperature values, TC, increase monotonically with x. For the compounds with high Co and low M content (0.6 ≤ x ≤ 1 and y = 1.6) the situation is rather different. Starting with the 3:29 stoichiometry a disordered variant of the hexagonal Th2Ni17-type structure is formed. In Y3(Fe1−xCox)29−yCry the monoclinic 3:29 structure is retained if the amount of the stabilizing element is increased. The TC values of the compounds are reduced; this should be attributed to the larger Cr content. The same behavior is observed in the case of Nd based products with 0.6 ≤ x ≤ 1 stabilized by Cr or Mn.