Quantum Spin Liquid in Frustrated One-DimensionalLiCuSbO4

Abstract

A quantum magnet, LiCuSbO 4 , with chains of edge-sharing spin-½ CuO 6 octahedra is reported. While short-range order is observed for T < 10 K, no zero-field phase transition or spin freezing occurs down to 100 mK. Specific heat indicates a distinct high field phase near the 12 T saturation field. Neutron scattering shows incommensurate spin correlations with q = (0.47±0.01)π/a and places an upper limit of 70 µeV on any spin gap. Exact diagonalization of 16-spin easy-plane spin-½ chains with competing ferro-and antiferromagnetic interactions (J 1 = -75 K, J 2 = 34 K) accounts for the T > 2 K data. PACS: 75.10.Jm, 75.30.Kz, 75.40.Cx, 75.30.Et 2 The Heisenberg spin-½ chain is one of very few quantum critical systems to be realized in a crystalline solid. An element of frustration is added by next-nearest-neighbor (NNN) interactions (J 2 ). [1][2][3] In such systems, theoretical work [4][5][6][7][8][9] indicates that qualitatively different quantum phases are possible as a function of α = J 2 /J 1 , axial exchange anisotropy, ∆, and the applied field h = gµ B H/|J 1 |. Finite values of α are observed in copper oxide spin-chains formed by corner-or edge-sharing Jahn-Teller distorted CuO 6 polyhedra. [10][11][12][13][14][15][16][17] While the sign and magnitude of J 1 is dependent on the <Cu-O-Cu bond angles, J 2 is always antiferromagnetic (AFM), ensuring frustration. For FM-AFM chains with ferromagnetic (FM) near-neighbor (NN) interactions (J 1 < 0), theory indicates a quantum critical point (QCP) at α c = -0.25, ∆ = 1, 18,19 which separates a gapless FM state (α > α c ) from a short-range ordered (SRO) phase with a small yet finite gap (α < α c ). 20Dimer, spiral, vector-chiral and multipolar phases have been predicted as a function of α, ∆ and h. 4,6,8 Interest has been further amplified by the observation that ferroelectricity accompanies magnetic ordering in some of these systems. 14,21,22 Known spin-½ FM-AFM chains span a wide range of α and include Li 2 CuO 2 , 17,21,22 Here we present the structure and magnetic properties of the one-dimensional (1D) spin chain compound LiCuSbO 4 . Due to weak inter-chain interactions it has no 3D ordering down to 100 mK and can be driven to a saturated-FM phase above the experimentally accessible field <µ o H s > = 12 T. The magnetic susceptibility, isothermal magnetization and specific heat can be simultaneously modelled for T > 2 K using the approximate spin Hamiltonian:Here θ is the angle between the applied field, h, and the unique molecular axis, z. The parameters J 1 = -75K, α = -0.45, and ∆ = 0.83 account for the main features in the thermomagnetic data and are also consistent with the magnetic excitations measured by inelastic neutron scattering.Powder samples of LiCuSbO 4 were prepared using a ceramic synthesis. 25LiCuSbO 4 has an orthorhombic structure 26, 27 related to that of LiFeSnO 4 . 28Rietveld analysis 29 of powder neutron diffraction data acquired on the BT1 diffractometer at NIST 30 was carried out using FULLPROF. 31The final fit, with the corr...

Формирование в системе (Sm-=SUB=-1-y-=/SUB=-Gd-=SUB=-y-=/SUB=-)-=SUB=-0.55-=/SUB=-Sr-=SUB=-0.45-=/SUB=-MnO-=SUB=-3-=/SUB=- манганитов фазы бесщелевой Z-=SUB=-2-=/SUB=--спиновой жидкости в нулевом магнитном поле: топологические фазовые переходы в состояния с низкой и высокой плотностью 2D-вихревых пар, индуцированных магнитным полем

“…Система спинов не может или вообще быть магнитно упорядоченной, или температура упорядочения оказывается значительно ниже температуры Кюри−Вейсса θ CW . Эти так называе-мые геометрически фрустрированные системы включа-ют различные классы материалов [24][25][26][27][28][29][30][31][32][33].…”

Spin-flop and antiferromagnetic phases of the ferromagnetic half-twist ladder compounds Ba3Cu3In4O12and Ba3Cu3Sc4O12

“…The half-twist geometry results in a different magnetic exchange pathway than in other 1D Cu 2+ chains with FM J 1 . [6][7][8][9][10][11][12][13] Unlike Exchange constants J are difficult to assign or compute because they are small on the scale of electronic energies and depend on both direct overlap between magnetic centres and through-bond pathways. We considered J 22 > 0 in figure 1b between Cu2 in the same rung but did not find improved fits.…”

“…Spin-1/2 chains of Cu 2+ with FM exchange J 1 < 0 have recently been identified in oxides [6][7][8][9][10][11][12][13] on either side of the quantum critical point [14], α c = −1/ 4, that is the exact boundary between a FM and a singlet ground state (GS) for isotropic exchange. Theory indicates the possibility of exotic ground states (GS) in FM/AFM chains with isotropic or anisotropic exchange [15][16][17][18][19][20].…”

Multipolar phase in frustrated spin-1/2 and spin-1 chains

“…[1,38,39]. It is hidden in nature, although the probes like the INS [28,40] and the resonant inelastic X-Ray scattering (RIXS) [41] methods can indirectly measure these phases. The nematic phase in LiCuVO 4 compound is confirmed by using the INS data of dynamical structure factor [40], and NMR data of this compound shows a sharp single and solitary line which moves with magnetic field [42,43].…”