To investigate the spin state of azurite, Cu3(CO3)2(OH)2, we have measured the thermal conductivity along the c-Axis, κc, perpendicular to the spin diamond chains. It has been found that the temperature dependence of κc shows a broad peak at ∼100 K, which is explained as being due to the strong phonon scattering by the strong spin fluctuation owing to the spin frustration at low temperatures below ∼100 K. Furthermore, it has been found that the temperature dependence of κc shows another peak at low temperatures below 20K and that κc is suppressed by the application of magnetic field along the c-Axis at low temperatures below ∼35 K. In high magnetic fields above ∼8 T at low temperatures below ∼6K, it has been found that κc increases with increasing field. The present results have indicated that both spin-singlet dimers with a spin gap of ∼35K and antiferromagnetically correlated spin chains with the antiferromagnetic exchange interaction of ∼5.4K are formed at low temperatures, which is consistent with the recent conclusion by Jeschke et al. [Phys. Rev. Lett. 106, 217201 (2011)] that the ground state of spins in azurite in zero field is a spin-fluid one. In addition, a new quantum critical line in magnetic fields at temperatures above 3K has been proposed to exist.
ASJC Scopus subject areas
- Physics and Astronomy(all)