Excitation Spectrum and Superexchange Pathways in the Spin Dimer VODPO_4 . 1/2 D_2O
arXiv:cond-mat/9704093 · doi:10.1103/PhysRevLett.78.4998
Abstract
Magnetic excitations have been investigated in the spin dimer material VODPO_4 \cdot 1/2 D_2O using inelastic neutron scattering. A dispersionless magnetic mode was observed at an energy of 7.81(4) meV. The wavevector dependence of the scattering intensityfrom this mode is consistent with the excitation of isolated V^{4+} spin dimers with a V-V separation of 4.43(7) Ã . This result is unexpected since the V-V pair previously thought to constitute themagnetic dimer has a separation of 3.09 Ã . We identify an alternative V-V pair as the likely magnetic dimer, which involves superexchange pathways through a covalently bonded PO_4 group. This surprising result casts doubt on the interpretation of (VO)_2P_2O_7 as a spin ladder.
4 pages, 4 postscript figures - identical to previous paper but figure 2 and 3 hopefully more compatible .ps