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

¹ INFN-Laboratori Nazionali di Frascati - Via E. Fermi 40, I-00044 Frascati, Italy
² Institut für Theoretische Physik, Leibniz Universität Hannover - D-30167 Hannover, Germany
³ Department of Theoretical Physics, Yerevan State University - Alex Manoogian 1, 0025 Yerevan, Armenia
⁴ ICTP - Strada Costiera 11, I-34151 Trieste, Italy
⁵ Departamento de Ciencias Exatas, Universidade Federal de Lavras - CP 3037, 37200000, Lavras, MG, Brazil

Received: 23 October 2013
Accepted: 10 February 2014

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, , in which 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.