| We study a frustrated quasi-one-dimensional Ising model that describes the magnetic degrees of freedom of Ca3Co2O6. The models comprises a triangular array of Co chains with dominant intra-chain ferromagnetic coupling and weak inter-chain antiferromagnetic exchange. By using unconstrained Mean Field and Quantum Monte Carlo techniques, we show that a quasi-continuous sequence of long-period spin-density-wave (SDW) orders are stabilized along the Co chains in the intermediate-temperature regime. The origin of these micro-phases is related to the frustrated inter-chain coupling that leads to solitons, phasons, and devil's staircases similar to the ones that appear in the well-known axial next-nearest-neighbor Ising (ANNNI) model. At low enough temperatures, the Co chains become ferromagnetic in equilibrium and a three-sublattice (up-up-down) structure is formed in the triangular lattice of Co chains. The quasi-continuous change of the SDW period along the Co chains in the intermediate-temperature regime implies the existence of a number of metastable states, whose significant contribution to the experimentally observed slow dynamics is discussed. Our results explain recent neutron scattering experiments. |
|