Finite Temperature Simulations of the Frustrated S=1/2 Chains

Thermodynamical properties of the one-dimensional S=1/2 Heisenberg model with dimerized nearest and uniform next-nearest neighbors interactions, applicable to CuGeO3 and Pb[Cu(SO4)(OH)2] compounds, are studied by the numerically exact quantum transfer-matrix method. Suzuki-Trotter formula is used to obtain a classical system with spin σ=3/2 and effective interactions between nearest neighbors only . Magnetic specific heat and magnetic susceptibility curves are calculated and compared with experimental results in a wide temperature range giving estimates of the coupling parameters in the model proposed for CuGeO3 and Pb[Cu(SO4)(OH)2]. (author)