MAGNETIC-PROPERTIES OF HIGH-TEMPERATURE SUPERCONDUCTORS - A SPIN LIQUID APPROACH

We argue that strongly correlated two dimensional electrons form a spi n liquid in some regimes of density and temperature and give the theor y of the magnetic properties of this spin liquid using a representatio n in terms of fermions interacting with a gauge field. We show that th is state is characterized by anomalous power law spin correlations and discuss the implications of these correlations for the temperature de pendence of NMR relaxation rates 1/T-1 and 1/T-2 and for the uniform s usceptibility. We also discuss the transition from the spin liquid to antiferromagnet and the critical behavior of these properties at the t ransition. We compare these theoretical results with data on high T-c superconductors. Finally, we discuss the formation of a spin gap due t o the spin exhange interaction between adjacent layers in bilayer mate rials.