Field induced crossover in antiferromagnetic spin-frustrated clusters: Influence of static and dynamic structural deformations

We propose a theoretical study of the magnetic behavior of spin frustrated trinuclear clusters in the region of the field induced crossover of the levels which are crucial for the description of the static magnetization and dynamic behavior in a sweeping field. The emphasis is made on a competitive role of the antisymmetric (AS) exchange and static structural distortions of the metal center network as well as on the consequences of the dynamic pseudo Jahn–Teller (JT) instability that is closely related to spin frustration. The structural conformations are shown to be controlled by the magnetic field in the anticrossing region (magnetoelastic coupling). We employ the three-spin model for the cluster anion present in K6[V15IVAs6O42(H2O)]·8H2O (V15 cluster) and analyze the role of different components of AS exchange in the shape of the magnetic susceptibility vs field. Both types of deformations (static and dynamic) are shown to be competitive to the AS exchange and tend to reduce the magnetic anisotropy caused by the AS exchange.