Infrared study of neodymium-copper exchange interaction in Nd2CuO4

We present an infrared transmission study of Nd2CuO4 Kramers doublets as a function of temperature and polarization. Lifting of the J = 9/2, 11/2, 13/ 2 and 15/2 Kramers doublets degeneracies of the order of few cm(-1) is obse rved which we ascribe to the exchange coupling of the Nd spins to the Cu su bsystem. In particular, we show that the doublet splittings data retrace th e Nd2CuO4 spin reorientation transitions and imply that the Nd-Cu coupling is strongly anisotropic. This finding supports a model used earlier to inte rpret the spin reorientation transitions as well as the spin-wave excitatio n gap data. (C) 1999 Elsevier Science B.V. All rights reserved.