Magnetic Properties of GdCl3 from Gd3+ Pair Measurements in LaCl3 and EuCl3

Abstract

Previous EPR measurements on Gd³⁺ pairs in LaCl₃ have shown that the interactions between nearest and next‐nearest neighbors are accurately described by isotropic bilinear exchange and magnetic dipole coupling, and they indicated that the ferromagnetic ordering of GdCl₃ at 2.2°K is due to dominant next‐nearest neighbor exchange. Similar measurements have now been made using EuCl₃ as the host lattice. The results are similar to those in LaCl₃, and since the lattice spacing in EuCl₃ is very close to that of GdCl₃, it is now possible to use the interaction constants measured for the Gd³⁺ pairs to make quantitative predictions of magnetic bulk properties of GdCl₃. Excellent agreement is found for the high‐temperature susceptibility; for the specific heat, there is a small discrepancy. The measured interaction constants are close to one of a set of values recently used by Marquard to predict some highly anomalous spin‐wave spectra for GdCl₃.