Cross-over from an incommensurate singlet spiral state with a vanishingly small spin-gap to a valence bond solid state in dimerized frustrated ferromagnetic spin-chains

Cliò Efthimia Agrapidis, Stefan-Ludwig Drechsler, Jeroen van den Brink +1

Motivated by the magnetic properties of the spin-chain compounds LiCuSbO${}_4$$\equiv$LiSbCuO${}_4$ and Rb${}_2$Cu${}_2$Mo${}_3$O${}_{12}$, we study the ground state of the Heisenberg chain wi…