The experimental study of the magnetic field dependence of specific heat in S = 12 quantum-spin chain CuSO4 · 5H2O

The magnetic specific heat measurements were performed on monocrystalline CuSO4·5H2O in a magnetic field from 0 up to T applied in a direction parallel to the easy axis at temperatures 415, 615 and 815 mK. The specific heat as a function of the applied magnetic field exhibits behaviour that cannot be accounted for by the spin-wave approximation.