Microscopic model of (CuCl)LaNb2O7 : Coupled spin dimers replace a frustrated square lattice
Year: 2010
Type: article
Abstract: We present a microscopic model of the spin-gap quantum magnet $(\text{CuCl}){\text{LaNb}}_{2}{\text{O}}_{7}$, previously suggested as a realization of the spin-$\frac{1}{2}$ frustrated square lattice. Taking advantage of the precise atomic positions from recent crystal structure refinement, we evaluate individual exchange integrals and construct a minimum model that naturally explains all the available experimental data. Surprisingly, the deviation from tetragonal symmetry leads to the formation of spin dimers between fourth neighbors due to a Cu-Cl-Cl-Cu pathway with an antiferromagnetic exchange ${J}_{4}\ensuremath{\simeq}25\text{ }\text{K}$. The total interdimer exchange amounts to 12--15 K. Our model is in agreement with inelastic neutron-scattering results and is further confirmed by quantum Monte Carlo simulations of the magnetic susceptibility and the high-field magnetization. We establish $(\text{CuCl}){\text{LaNb}}_{2}{\text{O}}_{7}$ as a nonfrustrated system of coupled spin dimers with predominant antiferromagnetic interactions and provide a general perspective for related materials with unusual low-temperature magnetic properties.
Source: Physical Review B
Authors: Alexander A. Tsirlin, Helge Rosner
Language: Latvian
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2094490505