Inelastic neutron scattering study of the spin-gap cuprate β-AgCuP O4

We studied magnetism of β-AgCuP O4 using inelastic neutron scattering and magnetic susceptibility measurements on powder samples. A well-defined asymmetric broad inelastic peak was observed at 6.2 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 K can explain the experimental results quantitatively. Our results are consistent with the prediction of Yahia [Inorg. Chem. 45, 5501 (2006)].