Magnetic Behavior of Spin-1/2 Frustrated System Hg_2Cu_2F_6S(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

概要

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Experimental studies have been carried out on geometrically frustrated quantum spins of Cu^<2+> ions of Hg_2Cu_2F_6S with pyrochlore structure. No magnetic and structural phase transitions have been observed in the temperature (T) range down to 2K. The magnetic correlation length ξ deduced from the T dependence of the NMR longitudinal relaxation rate is found to be as small as the atomic distance even at T much lower than the Cu^<2+>-Cu^<2+> exchange coupling energy J〜100K. With decreasing T from 〜200K, the NMR Knight shift first increases, has a maximum at 〜90K and decreases rather rapidly. This low-T behavior suggests that the system approaches the spin-liquid state. The upturn of the uniform magnetic susceptibility observed in the very low T region with decreasing T is due to lattice imperfections, and effects of these imperfections can be considered to be an origin of the large broadening of the NMR spectra observed at low T.
社団法人日本物理学会の論文
2007-08-15