UCL Discovery

Abstract

The frustrated magnet clinoatacamite, gamma-Cu-2(OH)(3)Cl, is attracting a lot of interest after suggestions that at low temperature it forms an exotic quantum state termed a Valence Bond Solid (VBS) made from dimerised Cu2+ (S = 1/2) spins.[12] Key to the arguments surrounding this proposal were suggestions that the kagome planes in the magnetic pyrochlore lattice of clinoatacamite are only weakly coupled, causing the system to behave as a quasi-2-dimensional magnet. This was reasoned from the near95 degrees angles made at the bridging oxygens that mediate exchange between the Cu ions that link the kagome planes.Recent work pointed out that this exchange model is in appropriate for gamma-Cu-2(OH)(3)Cl, where the oxygen is present as a mu(3)-OH.[11] Further, it used symmetry calculations and neutron powder diffraction to show that the low temperature magnetic structure (T < 6 K) was canted and involved significant spin ordering on all the Cu2+ spins, which is in compatible with the interpretation of simultaneous VBS and Neel ordering. Correspondingly, clinoatacamite is best considered a distorted pyrochlore magnet. In this report we show detailed inelastic neutron scattering spectra and revisit the responses of this frustrated quantum magnet.