Neutron scattering study of Sr2Cu3O4Cl2

Y. J. Kim, R. J. Birgeneau, F. C. Chou, M. Greven, M. A. Kastner, Y. S. Lee, B. O. Wells, A. Aharony, O. Entin-Wohlman, I. Ya Korenblit, A. B. Harris, R. W. Erwin, G. Shirane

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We report a neutron scattering study on the tetragonal compound Sr2Cu3O4Cl2, which has two-dimensional (2D) interpenetrating CuI and CuII subsystems, each forming a S = 1/2 square lattice quantum Heisenberg antiferromagnet (SLQHA). The mean-field ground state is degenerate, since the intersubsystem interactions are geometrically frustrated. Magnetic neutron scattering experiments show that quantum fluctuations lift the degeneracy and cause a 2D Ising ordering of the CuII subsystem. Due to quantum fluctuations a dramatic increase of the CuI out-of-plane spin-wave gap is also observed. The temperature dependence and the dispersion of the spin-wave energy are quantitatively explained by spin-wave calculations which include quantum fluctuations explicitly. The values for the nearest-neighbor superexchange interactions between the CuI and CuII ions and between the CuII ions are determined experimentally to be JI-II= -10(2) meV and JII = 10.5(5) meV, respectively. Due to its small exchange interaction JII, the 2D dispersion of the CuII SLQHA can be measured over the whole Brillouin zone with thermal neutrons, and a dispersion at the zone boundary, predicted by theory, is confirmed. The instantaneous magnetic correlation length of the CuII SLQHA is obtained up to a very high temperature, T/JII≈0.75. This result is compared with several theoretical predictions as well as recent experiments on the S = 1/2 SLQHA.

Original languageEnglish
Article number024435
Pages (from-to)244351-2443519
Number of pages2199169
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number2
StatePublished - 2001


FundersFunder number
National Science Foundation
Directorate for Mathematical and Physical Sciences9423101


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