SPIN DYNAMICS OF THE QUASI-2-DIMENSIONAL HEISENBERG-ANTIFERROMAGNET EU2CUO4

The microwave measurements of dielectric Eu2CuO4 crystal with no const ant magnetic field applied have revealed homogeneous (q = 0), well-def ined spin-wave excitations (with the decay gamma < < omega(0)) of a sp in-wave type frequency omega(0) in a wide temperature range including temperatures much higher than the Neel point T-N. It is shown that the existence of such excitations in the spin subsystem may be responsibl e for by the effect of random Ising fields generating in an orbital su bsystem in the orbital glass state.