Magnetic State of the Geometrically Frustrated Quasi-One-Dimensional Spin System Cu${}_3$Mo${}_2$O${}_9$ Studied by Thermal Conductivity

Abstract

We have measured the thermal conductivity of the geometrically frustrated quasi-onedimensional spin system Cu${}_3$Mo${}_2$O${}_9$ in magnetic fields. A contribution of the thermal conductivity due to spins has been observed in the thermal conductivity along the spin chains. The thermal conductivity due to phonons, ${\kappa }_{\mathrm{phonon}}$, has been found to decrease by the application of a magnetic field, which has been explained as being due to the reduction in the spin gap originating from the spin-singlet dimers. Moreover, it has been found that ${\kappa }_{\mathrm{phonon}}$ increases with increasing field in high fields above ~7 T at low temperatures. This suggests the existence of a novel field-induced spin state and is discussed in terms of the possible spin-chirality ordering in a frustrated Mott insulator.

15 pages, 7 figures, Journal of the Physical Society of Japan (2015)