High pressure sequence of Ba₃NiSb₂O₉ structural phases: new S = 1 quantum spin-liquids based on Ni²⁺

2011/08/14 by J. G. Cheng, G. Li, L. Balicas +4
Physics and Astronomy · #cond-mat.str-el #cond-mat.other

paper · pdf · doi:10.1103/physrevlett.107.197204

published as Phys. Rev. Lett., 107, 19720 (2011) · 4 pages, 3 figures

arxiv created 2011/08/14 · arxiv updated 2011/11/08

Abstract

By using a high pressure, high temperature (HPHT) technique, the antiferromagnetically ordered (T_N = 13.5 K) 6H-A phase of Ba₃NiSb₂O₉ was transformed into two new gapless quantum spin liquid(QSL) candidates with S=1 (Ni²⁺) moments: the 6H-B phase with a Ni²⁺-triangular lattice and the 3C-phase with a Ni²⁺-three-dimensional (3D) edge-shared tetrahedral lattice. Both compounds show no magnetic order down to 0.35 K despite Curie-Weiss temperatures θ_CW of -75.5 K (6H-B) and -182.5 K (3C), respectively. Below ∼ 25 K the magnetic susceptibility of the 6H-B phase saturates to a constant value χ₀ = 0.013 emu/mol which is followed below 7 K, by a linear-temperature dependent magnetic specific heat (C_M) displaying a giant coefficient γ = 168 mJ/mol-K². Both observations suggest the development of a Fermi-liquid like ground state characterized by a Wilson ratio of 5.6 in this insulating material. For the 3C phase, the C_M ∝ T² behavior indicates a unique S=1, 3D QSL ground-state.

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