INFLUENCE OF ND MAGNETIC SUBSYSTEM ON SPIN-REORIENTATION PHASE-TRANSITION IN ND2CUO4 AT LOW-TEMPERATURE

Acoustic measurements on Nd2CuO4 single crystals have recently reveale d a ferroelastic phase transition at about T-c = 5 K. In view of the s trong magnetoelastic coupling in the compound it was attributed to an additional reorientation of Cu spins. In the present report it is show n that this transition can be successfully described if one takes the Nd magnetic subsystem into account explicitly. This approach requires treating a phenomenological Hamiltonian within invariants of the fourt h order in spins only, which is natural for a tetragonal symmetry of t he system. Complementary information about the strength of Nd-Nd inter actions has been derived. (C) 1997 American Institute of Physics.