Synthesis and magnetic properties of novel compounds R-3(Fe,T)(29) (R=Y, Ce, Nd, Sm, Gd, Tb, and Dy; T=V and Cr)

A systematic investigation of structure and intrinsic magnetic properties of the novel compounds R-3(Fe,T)(29) (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy; T = V and Cr) has been performed. The lattice constants and unit cell volume decrease with increasing the rare-earth atomic number from R = Nd to Dy, except for Ce, reflecting the lanthanide contraction. The Curie temperature increases from R = Ce to Gd and decreases from Gd to Dy, respectively, with increasing atomic number and Gd3Fe29-xTx has the highest Curie temperature for each series of R3Fe29-xTx (T = V or Cr) compounds. The saturation magnetization of R3Fe29-xTx at 4.2 K decreases gradually from R = Nd to Dy with increasing atomic number, except for Ce, in each series of R3Fe29-xTx. It is suggested that the Ce ion in Ce3Fe29-xTx valence fluctuated which leads to the unusual magnetic properties. The spin reorientations of the easy magnetization direction of R3Fe29-xTx are observed at around 230, 230; and 160 K for R = Nd, Sm, and Tb when T = V, and at around 230 and 180 K for R = Nd and Tb when T = Cr, respectively. First order magnetization processes are observed around 5.7 T for Sm3Fe26.7V2.3 and 4 T for Sm3Fe24.0Cr5.0 at 4.2 K, 2.0 T for Tb3Fe28.0V1.0, and 2.3 T for Tb3Fe28.0Cr1.0 at room temperature. A phenomenological analysis shows that the saturation magnetization of R3Fe29-xTx compounds with a low T concentration can be roughly calculated based on a combination of those of the 2:17R and 1:12 units in a ratio of 1:1. (C) 1997 American Institute of Physics.