INFLUENCE OF CE-DOPING ON THE MAGNETIC EXCITATIONS OF ND IN ND2-XCEXCUO4

We present a study of the spin-wave excitations of Nd in Nd2-xCexCuO4( x = 0, 0.09, 0.15, 0.18) by inelastic neutron scattering. Upon Ce-dopi ng one observes a softening of the spin-wave branches. This is mainly explained by the decrease of the Cu-Nd exchange field at the Nd site, while the Nd-Nd exchange interactions remain almost unchanged. Consequ ently a high density of states of spin-wave excitations at low energie s is created. The resulting calculated specific-heat shows a large gam ma = C/T-value at low temperatures, which indicates that the novel hea vy-fermion behavior in these compounds is mainly due to magnetic corre lations of the Nd ions. (C) 1998 Elsevier Science B.V. All rights rese rved.