Neutronenstreuexperimente und Messung des spezifischen Widerstands zur Untersuchung der Kristallfeld-Grundzustände in Seltenen-Erd-Hexaboriden

By means of magnetic neutron scattering and resistivity measurements the rare earth hexaborides $Ce_{x}La_{1-x}B_{6}, Pr_{x}La_{1-x}B_{6}$ and $Nd_{x}La_{1-x}B_{6}$ were investigated to determine the splitting of the crystal field ground states in the magnetically ordered state. In all three systems a splitting of the ground state was observed which amounts to about 2 meV in the full compounds (x =1). In diluted systems (x < 1) the splitting is reduced, as the 4f-electron interaction is diminished as a consequence of an enlarged average 4f-electron distance. In case of $PrB_{6}$ and $NdB_{6}$ we were able to establish the dispersive character of the splittings which indicates the collective origine of the excitations (magnons)