Inelastic neutron scattering study of the spin-gap cuprateβ−AgCuPO4

Abstract

We studied magnetism of $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{Ag}\mathrm{Cu}\mathrm{P}{\mathrm{O}}_{4}$ using inelastic neutron scattering and magnetic susceptibility measurements on powder samples. A well-defined asymmetric broad inelastic peak was observed at $6.2\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ in constant-$Q$ (scattering vector) scan spectra, indicating spin-gap excitation. From results of these measurements, we have obtained that the strongest exchange interaction exists in a Cu-O-P-O-Cu path in spite of the existence of Cu-O-Cu paths and that the antiferromagnetic alternating chain model with two exchange interaction values of 80 and $14\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ can explain the experimental results quantitatively. Our results are consistent with the prediction of Yahia et al. [Inorg. Chem. 45, 5501 (2006)].