THE SINGLET-TRIPLET MAGNETISM IN THE CUPRATES

The spin subsystem of the copper oxides within the polar Jahn-Teller C uO4 center model is a two-component spin liquid and corresponds to a s inglet-triplet magnet with, in general, multiparametric (non)collinear spin configurations. In the framework of a modified mean field approx imation several collinear spin orders are discussed including both qui te trivial singlet or triplet states and a purely quantum singlet-trip let mixed state. The spectrum of the elementary excitations is calcula ted by the Green's function method. We conjecture that charge fluctuat ions in a singlet-triplet magnet are accompanied by a modulation of th e on-site spin density that results in a possibility to observe the ch arge fluctuations in the inelastic neutron scattering and the spin lat tice relaxation experiments. The suggested model represents a new appr oach to the description of the spin system of the cuprates. (C) 1998 E lsevier Science B.V. All rights reserved.