Onset of magnetism in concentrated ternary alloys II: Laves phase compounds A(Fe1-xBx)2 (A = Y,Zr, U; B = Mn,Co and Al)

The onset of magnetism as a function of concentration and the magnetic properties of nine ternary Laves phase systems A(Fe_1-xB_x)₂ (A=Y, Zr, U; B=Mn, Co and Al) are discussed in terms of homogeneous and heterogeneous models based on the SEW model and the Landau theory of phase transition of second order. A significant influence of the nomagnetic elements Y, Zr and U upon the Fe magnetic moment substituted by Mn, Co and Al is observed. Low temperature freezing phenomena affect the magnetization process around the critical concentration x_c in Y and Zr compounds while they seem to be of minor importance for the U systems. Comparing the magnetic properties of these nine systems implies that the magnetization process becomes more homogeneous in the sequence of Y-, Zr- and U(Fe, B)₂ compounds. This - together with volume considerations and the different magnetovolume effects observed as well as susceptibility measurements lead to the suggestion that the Fe moment tends to become more delocalized as one proceeds from Y to U compounds as a consequence of the growing extent to which Y, Zr, U d-electrons are hybridized with the 3d electrons. Furthermore, U can be regarded as tetravalent in these Laves phase compounds, except UAl₂, in which presumably an admixture of U³⁺ and U⁴⁺ occurs.