Electronic structure and magnetic properties of Gd(Co1-xMx)2 compounds, M=Ga, Si, Ge

We report the results of measurements of the magnetic susceptibility and the crystal and electronic structures of the polycrystalline intermetallic compounds Gd(Co1-xMx)(2),M=Ga, Si, Ge, and the results of the electrical resistivity measurements for these systems when M=Ga and Si. The dependence of the Curie temperature, T-C, and the lattice constant versus concentration, x, of the M element was established for all investigated systems. The influence of the partial substitution of Ga for Co is reflected in a drastic change in T-C with concentration x. This result differs very much from that when M=Si, where we do not detect a change in the T-C(x) and also when M=Ge, where we observe a very weak dependence of the Curie temperature on x. The electronic structure of all systems was studied by using X-ray photoelectron spectroscopy (XPS). From the XPS spectra in the valence band region we derive that there is hybridization between the Co d states and the M p states. This effect changes the shape of the valence band in the vicinity of the Fermi level. The observed changes in the electronic structure correlate with the change in magnetic properties of the investigated systems. (C) 2002 Elsevier Science B.V. All rights reserved.