PUB - Publikationen an der Universität Bielefeld

The thermodynamic quantities (spin-spin correlation functions < S(0)S(n)>, correlation length xi, spin susceptibility chi, and specific heat C(V)) of the frustrated one-dimensional J(1)-J(2) Heisenberg ferromagnet with arbitrary spin quantum number S below the quantum critical point, i.e., for J(2) < vertical bar J(1)vertical bar/4, are calculated using a rotation-invariant Green-function formalism and full diagonalization as well as a finite-temperature Lanczos technique for finite chains of up to N = 20 sites. The low-temperature behavior of the susceptibility chi and the correlation length xi are well described by chi = 2/3 S(4) (vertical bar J(1)vertical bar - 4J(2)) T(-2) + AS(5/2) (vertical bar J(1)vertical bar - 4J(2))(1/2) T(-3/2) and xi = S(2) (vertical bar J(1)vertical bar - 4J(2)) T(-1) + BS(1/2) (vertical bar J(1)vertical bar - 4J(2))(1/2) T(-1/2) with A approximate to 1.1 ... 1.2 and B approximate to 0.84 ... 0.89. The vanishing of the factors in front of the temperature at J(2) = vertical bar J(1)vertical bar/4 indicates a change of the critical behavior of chi and xi at T -> 0. The specific heat may exhibit an additional frustration-induced low-temperature maximum when approaching the quantum critical point. Such a maximum appears for S = 1/2 and S = 1, but was not found for S > 1.