Spin Dynamics of the Spin-1/2Kagome Lattice AntiferromagnetZnCu3(OH)6Cl2

Abstract

We have performed thermodynamic and neutron scattering measurements on the S=1/2 kagomé lattice antiferromagnet ZnCu3(OH)6Cl2. The susceptibility indicates a Curie-Weiss temperature of theta CW approximately = -300 K; however, no magnetic order is observed down to 50 mK. Inelastic neutron scattering reveals a spectrum of low energy spin excitations with no observable gap down to 0.1 meV. The specific heat at low-T follows a power law temperature dependence. These results suggest that an unusual spin liquid state with essentially gapless excitations is realized in this kagomé lattice system.

Orbital switching in a frustrated magnet

“…Such a transition is an order-disorder transition associated with the orbital degree of freedom. Similar orbital ordering phenomena are observed in various 3d transition metal compounds such as the perovskite manganite LaMnO 3 (19). In contrast, because of the strong Jahn-Teller effect for the Cu 2 + ion, no corresponding orbital disordered state has been observed in copper compounds even at HT; most compounds decompose before orbital disordering.…”

Numerical study of the thermodynamics of clinoatacamite

“…The x = 1 endmember of this family, herbertsmithite, has attracted interest as a strong candidate to display a spin liquid ground state on almost perfectly decoupled twodimensional (2D) kagomé layers. [5][6][7] However, the best available samples are likely not stoichiometric, 8 with a small fraction of Cu ions on the triangular lattice planes weakly (of order 1 K) coupled to the kagomé planes. 9 Materials such as YBaCo 4 O 7 10 and Y 0.5 Ca 0.5 BaCo 4 O 7 11 also feature alternating kagomé and triangular layers, but with a stacking that is structurally distinct from the pyrochlore lattice.…”

Impact of Mn–O–O–Mn superexchange pathways in a honeycomb lattice Mn oxide with small charge-transfer energy

“…The exchange interaction J in a Mott insulator is roughly given by −2t 2 /E g , where t is the transfer integral between the two localized orbitals and E g is the excitation energy across the Mott gap. In Mott insulators on frustrated lattices, spin-disordered systems including organic and inorganic materials [2][3][4][5][6] all have relatively small E g , suggesting that the smallness of E g or the closeness to the Mott transition would be important to realize the spin-disordered ground states.Various insulating transition-metal oxides are known as Mott insulators and can be classified into (i) the Mott-Hubbard type insulators where the Mott gap E g is mainly determined by the Coulomb interaction U between the transition-metal d electrons and (ii) the chargetransfer type insulators where E g is determined by the charge-transfer energy ∆ from the oxygen p state to the transition-metal d state [7]. Therefore, the smallness of E g can be obtained in transition-metal oxides with small U or small ∆.…”

“…The exchange interaction J in a Mott insulator is roughly given by −2t 2 /E g , where t is the transfer integral between the two localized orbitals and E g is the excitation energy across the Mott gap. In Mott insulators on frustrated lattices, spin-disordered systems including organic and inorganic materials [2][3][4][5][6] all have relatively small E g , suggesting that the smallness of E g or the closeness to the Mott transition would be important to realize the spin-disordered ground states.…”

“…The experimental spectrum has a sharp peak at ∼ 641. 5 [12]. We performed configuration-interaction (CI) cluster-model calculations [15] to obtain electronic parameters.…”