We present thermal expansion alpha, magnetostriction and specific heat C measurements of \tal, which shows a quantum phase transition from a spin-gap phase to a Neel-ordered ground state as a function of magnetic field around H_{C0}->4.8T. Using Ehrenfest's relation, we find huge pressure dependencies of the spin gap for uniaxial as well as for hydrostatic pressure. For T->0 and H->H_{C0} we observe a diverging Grueneisen parameter Gamma(T)=alpha/C, in qualitative agreement with theoretical predictions. However, the predicted individual temperature dependencies alpha(T) and C(T) are not reproduced by our experimental data.
@article{arxiv.cond-mat/0609348,
title = {Thermodynamics of the coupled spin-dimer system TlCuCl3 close to a quantum phase transition},
author = {T. Lorenz and S. Stark and O. Heyer and N. Hollmann and A. Vasiliev and A. Oosawa and H. Tanaka},
journal= {arXiv preprint arXiv:cond-mat/0609348},
year = {2009}
}
Comments
6 pages including 7 figures, contribution to the III Joint European Magnetic Symposia 2006, San Sebastian