Inelastic neutron scattering studies of the quantum frustrated magnet clinoatacamite, $\gamma$-Cu2(OD)3Cl, a proposed valence bond solid (VBS)

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 Cu${}^{2+}$ ($S=1/2$) spins.\cite{Lee_clinoatacamite} Key to the arguments surrounding this proposal were suggestions that the kagomé 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 near 95${}^{\circ }$ angles made at the bridging oxygens that mediate exchange between the Cu ions that link the kagomé planes. Recent work pointed out that this exchange model is inappropriate for $\gamma$-Cu${}_2$(OH)${}_3$Cl, where the oxygen is present as a ${\mu }_3$-OH.\cite{Wills_JPC} 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 Cu${}^{2+}$ spins, which is incompatible with the interpretation of simultaneous VBS and Néel 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.

Proceedings of The International Conference on Highly Frustrated Magnetism 2008 (HFM2008)

References in corpus (1)

• Magnetic ordering in Gd2Sn2O7: the archetypal Heisenberg pyrochlore antiferromagnet