Crossover from antiferromagnetic Kondo metal to Kondo insulator in Ce(Pt1-xNix)Sn alloys

Transport, magnetic, inelastic neutron scattering and high field magnetoresistance measurements have been made on Ce(Pt1-xNix)Sn alloys, in order to investigate the crossover from the antiferromagnetic Kondo metal (CePtSn) to the Kondo insulator (CeNiSn). Inelastic neutron scattering from CePtSn shows two well-defined crystal field excitations. These broaden with increasing Ni content x in Ce(Pt1-xNix)Sn. CeNiSn shows a single broad inelastic excitation. High field magnetoresistance of CePtSn and CePt0.5Ni0.5Sn shows good agreement with Schlottmann's J=1/2 Kondo impurity model. CeNiSn exhibits a large negative magnetoresistance (-41% at 20 T and 1.7 K) arising from the suppression of the energy gap with field. (orig.)