Spin Order by Quantum Frustration in Triangular Lattice Mott Insulator NaCrO2 : A Neutron Scattering Study

D. Hsieh; D. Qian; R. F. Berger; C. Liu; B. Ueland; P. Schiffer; Q. Huang; R. J. Cava; J. W. Lynn; M. Z. Hasan

paper

Spin Order by Quantum Frustration in Triangular Lattice Mott Insulator NaCrO2 : A Neutron Scattering Study

arXiv:1405.6184

Abstract

We report high resolution neutron scattering measurements on the triangular lattice Mott insulator Na $_{x}$ CrO $_{2}$ ( $x$ =1) which has recently been shown to exhibit an unusually broad fluctuating crossover regime extending far below the onset of spin freezing ( $T_{c} \sim$ 41K). Our results show that below some crossover temperature ( $T \sim 0.75 T_{c}$ ) a small incommensuration develops which helps resolve the spin frustration and drives three-dimensional magnetic order supporting coherent spin wave modes. This incommensuration assisted dimensional crossover suggests that inter-layer frustration is responsible for stabilizing the rare 2D correlated phase above 0.75 $T_{c}$ . In contrast to the host compound of 2D cobaltate superconductor such as Na $_{x}$ CoO $_{2}$ ( $ξ_{c} > 50$ Å), no magnetic long-range order is observed down to 1.5K ( $ξ_{c} < 16$ Å).

5 pages, 4 figures