The modification of low-temperature magnetic properties of the Fe-based double-zigzag single-chain magnet under irradiation

An exact solution for a generalized Ising model describing single-chain magnet [FeIII(Tp*)(CN)3]2FeII(bpmh)}·2H2O with alternating high-spin and low-spin iron ions and double-zigzag magnetic topology has been calculated making use of the transfer-matrix technique. The introduction of a statistical ensemble taking into account the presence of iron ions with high-spin (HS) and low-spin (LS) states made it possible to describe the modification of magnetic susceptibility under optical irradiation. It has been shown that joint implementation of iron ions with photoinduced magnetic states and non-magnetic intersite repulsion ions of these states is caused by the difference of the ionic radii of HSFeII and LSFeII leads to the quantum phase transitions in the system.