title: Spin correlations in the paramagnetic phase and ring exchange in La2CuO4.
abstract: Spin correlations in the paramagnetic phase of La(2)CuO(4) have been studied using polarized neutron scattering, with two important results. First, the temperature dependence of the characteristic energy scale of the fluctuations and the amplitude of the neutron structure factor are shown to be in quantitative agreement with the predictions of the quantum nonlinear sigma model. Second, a comparison of a high-temperature series expansion of the equal-time spin correlations with the diffuse neutron intensity provides definitive experimental evidence for ring exchange.
authors.affiliation: Department of Physics, University of Liverpool, Oliver Lodge Laboratory, UK.
authors.forename: A M
authors.initials: AM
authors.lastname: Toader
authors.forename: J P
authors.initials: JP
authors.lastname: Goff
authors.forename: M
authors.initials: M
authors.lastname: Roger
authors.forename: N
authors.initials: N
authors.lastname: Shannon
authors.forename: J R
authors.initials: JR
authors.lastname: Stewart
authors.forename: M
authors.initials: M
authors.lastname: Enderle