Raman study of Kramers doublets inNd2CuO4

Raman-scattering measurements involving the ${\mathrm{Nd}}^3$+-ion crystal field Kramers doublets in ${\mathrm{Nd}}_2$ ${\mathrm{CuO}}_4$ are reported. The observed splitting is attributed to the lifting of the Kramers degeneracy by the Nd-Cu exchange interaction. Below 150 K the splitting of these crystal-field excitations is nearly temperature independent. There are also small discontinuities in the amplitude ratio of the doublet components at 30 and 75 K. These discontinuities can be intepreted as arising from the direction reversal of the Nd magnetic moment following the direction reversal of the copper exchange field at these phase transitions.