CORRELATIONS OF THE ND MAGNETIC-MOMENTS AND THEIR INFLUENCE ON THE SPECIFIC-HEAT IN ND2-XCEXCUO4

We study the effect of Ce substitution on the magnetic excitations of Nd in Nd2-xCexCuO4 by inelastic neutron scattering. A strong softening of the spin waves upon doping is observed, due to a decrease of the C u-Nd exchange field at the Nd site. Consequently, a high spin-wave den sity of states is created at low energies, which leads ta giant gamma = C/T values at low temperatures. This demonstrates that the magnetism of the Nd ions is the only source of the large gamma values found in specific-heat experiments, i.e., Nd2-xCexCuO4 has to be excluded as a prototype of a novel heavy-fermion system.