Specific heat study of the field-induced magnetic ordering in the spin-gap system TlCuCl3 -: art. no. 134416

Specific heat measurements have been performed in the coupled dimer system TlCuCl3, which has a singlet ground state with the excitation gap Delta = 7.5 K. The cusplike anomaly indicative of the three-dimensional magnetic ordering was clearly observed in magnetic fields higher than the critical field N-g corresponding to the gap Delta. The phase boundary determined by the present specific heat measurements coincides with that determined by previous magnetization measurements. The phase boundary can he described by the power law [H-c(T) - H-g] proportional to T-phi with phi = 2.1(1). This result supports the magnon Bose condensation picture for the field-induced magnetic ordering in TlCuCl3.