Hamiltonian of the S =1/2 dimerized antiferromagnetic-ferromagnetic quantum spin chain BaCu2V2O8

The novel quantum magnet BaCu2V2O8 was recently discovered to be a rare physical realization of a one-dimensional antiferromagnetic-ferromagnetic dimerized chain which displays strongly correlated phenomena at elevated temperatures [E. S. Klyushina et al., Phys.Rev.B 93, 241109(R) (2016)]. This paper presents an extended study of the Hamiltonian of BaCu2V2O8 at base temperature. Static susceptibility and inelastic neutron scattering data are compared to several theoretical models. An analytical relation for the dynamic structure factor of the complex unit cell of BaCu(2)V(2)O(8 )is derived and used to identify the intrachain exchange paths. Further analysis using the first moment of the dynamic structure factor was employed to determine the exchange path responsible for the intradimer interaction. This analysis reveals that the dimer chain is formed by a dominant antiferromagnetic exchange interaction J(intra) = 40.92 meV which is realized via the Cu-O-V(II)-O-Cu superexchange path and a weak ferromagnetic coupling J(intra) = -11.97 meV which arises within the copper-oxygen double plaquettes.