Raman study of crystal-field excitations in Nd2CuO4 under pressure - art. no. 214106

The effect of hydrostatic pressure on crystal-field (CF) levels of Nd3+ in Nd2CuO4 has been studied. Raman spectroscopy was used to measure the pressu re dependences of two CF transitions near 750 cm(-1) and 1995 cm(-1) at T = 5 K. On the basis of the superposition model and an ab initio method we ca lculated the CF level energies as a function of pressure. Good agreement wi th the experimental data is found for the 750-cm(-1) excitation while devia tions in case of the 1995-cm(-1) transitions can be attributed to changes o f the free-ion parameters of the Hamiltonian. Pressure-induced changes in t he splitting of the 1995-cm(-1) doublet are interpreted considering the ani sotropy of the Nd-Cu exchange coupling. Experiments at T = 44 K indicate a possible pressure-induced magnetic reorientation transition similar to what was observed earlier around T = 30 K as a function of temperature.