Magnetic properties of GdPdAl single crystals

Single crystals of the intermetallic ternary compound GdPdAl, crystallizing in the hexagonal ZrNiAl-type structure, were grown by the Czochralski meth od. Lattice parameters, electrical resistivity, magnetic susceptibility giv e evidence of an isostructural phase transition from a high temperature mod ification HTM I phase to HTM II phase at 180 K. The jump related to this tr ansition causes a decrease of the lattice parameter a of 0.7% and an increa se of the lattice parameter c of 1.3% during the cooling process. These cha nges are responsible for some microcracks in the single crystal. Besides th e structural phase transition, magnetic ordering of the Gd sublattice is ob served at 48 K. At about 20 K a spin reorientation process may occur. The X PS measurements of GdPdAl reveal a dominating contribution of d electrons a t the Fermi level. For comparison the electronic structure of TbPdAl was al so examined. Both compounds reveal formation of a narrow Pd 4d band. Furthe r information on changes of the electronic structure at the isostructural p hase transition were obtained from the temperature dependence of the ESR li newidth. (C) 2001 Elsevier Science B.V. All rights reserved.