Static and dynamic magnetic properties of coupled spin-1/2antiferromagnetic chains

Abstract

Calculations of the thermodynamic quantities, and the spectra ofspinons, triplet excitations, and two-particle spin-singlet (ΔSz = 0,±1) excitations for a weakly coupled antiferromagneticS = 1/2 spin chain are made using a mean-field approximation for theinterchain couplings (J2) by the quantum Monte Carlo method. Themass gaps in these excitation spectra are estimated as functions ofthe interchain coupling. The critical field Hc, and thetemperatures at which the spinon and singlet gaps close (T1 andT2, respectively) are obtained. Some peculiarities of thestaggered magnetization, the specific heat, and the spin-spincorrelation function are found at T1 = 0.9J2, T2 = 1.5J2,Hc = 3.8J2, as determined by linear function fitting for J2/J1<0.15. The intrachain and interchain couplings, and the staggeredmagnetization for KCuF3, Sr2CuO3, and Ca2CuO3 areestimated, and mass gaps are predicted to exist in the spectra ofthe spinons and the singlet two-particle excitations.