Magnetization non-rational quasi-plateau and spatially modulated spin order in the model of the single-chain magnet, [{(CuL) 2Dy}{Mo(CN) 8}]·2CH3CN·H2O

Abstract

Using the exact solution in terms of the generalized classical transfer matrix method, we present a detailed analysis of the magnetic properties and ground-state structure of the simplified model of the single-chain magnet, trimetallic coordination polymer compound, L2− is N,N-propylenebis(3-methoxysalicylideneiminato). Due to the presence of highly anisotropic Dy3+ ions, this material is a unique example of the one-dimensional magnets with Ising and Heisenberg bonds, allowing exact statistical-mechanical treatment. We found two zero-temperature ground states corresponding to different parts of the magnetization curve of the material. The zero-field ground state is shown to be an antiferromagnetic configuration with spatial modulation of the local Dy3+ (which is proven to posses well-defined Ising-like properties due to the large anisotropy of g-factors) and composite spin of the quantum spin trimer Cu-Mo-Cu in the form "up"-"down"-"down"-"up". Another important feature of this compound is the appearance of the quasi-plateau at a non-rational value of magnetization due to the difference of the g-factors of the Cu- and Mo-ion in quantum spin trimers. The quasi-plateau is a nearly horizontal part of the magnetization curve where the corresponding zero-temperature ground state of the chain demonstrates slow, but monotonous dependence of the magnetization on the external magnetic field, while the z-projection of the total spin, is constant.