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We report on a member of the spin-disordered honeycomb lattice antiferromagnet in a quasi-one-dimensional cobaltate Ba3Co2O6(CO3)0.7. Resistivity exhibits as semimetallic along the face-sharing CoO6 chains. Magnetic susceptibility shows strongly anisotropic Ising-spin character with the easy axis along the chain due to significant spin-orbit coupling and a trigonal crystal field. Nevertheless, 135Ba NMR detects no indication of the long-range magnetic order down to 0.48 K. Marginally itinerant electrons possess large entropy and low-lying excitations with a Wilson ratio RW=116, which highlight interplays of charge, spin, and orbital in the disordered ground state. [ABSTRACT FROM AUTHOR]

The effects of pressure on a quantum spin liquid are investigated in an organic Mott insulator κ-(ET)2Ag2(CN)3 with a spin-1/2 triangular lattice. The application of negative chemical pressure to κ-(ET)2Cu2(CN)3, which is a well-known sister Mott insulator, allows for extensive tuning of antiferromagnetic exchange coupling, with J/kB=175-310 K, under hydrostatic pressure. Based on C13 nuclear magnetic resonance measurements under pressure, we uncover universal scaling in the static and dynamic spin susceptibilities down to low temperatures ~0.1kBT/J. The persistent fluctuations and residual specific heat coefficient are consistent with the presence of gapless low-lying excitations. Our results thus demonstrate the fundamental finite-temperature properties of a quantum spin liquid in a wide parameter range. [ABSTRACT FROM AUTHOR]

We have made 53Cr NMR measurements on polycrystalline and single-crystalline film samples to study the local electronic state of a half-metallic ferromagnet CrO2 which has the rutile structure with one crystallographically equivalent Cr site. We observe two kinds of 53Cr NMR spectra in the ferromagnetic state of both the samples. An analysis on the hyperfine field shows the presence of two Cr sites with different orbital occupancies, suggesting that a local orbital order takes place with breaking the local symmetry in the rutile structure. This may be ascribed to the negative charge transfer between chromium and oxygen ions. [ABSTRACT FROM AUTHOR]