Structural distortion and frustrated magnetic interactions in the layered copper oxychloride [CuCl]LaNb(2)O(7)

TL;DR

This study computationally investigates the layered copper oxychloride [CuCl]LaNb(2)O(7), revealing a Jahn-Teller distortion, complex spin interactions, and frustration effects that influence its magnetic properties.

Contribution

It uncovers a Jahn-Teller distortion in [CuCl]LaNb(2)O(7) that alters local structure and spin interactions, providing new insights into its magnetic behavior.

Findings

Identification of a Jahn-Teller distortion in the structure

Complex three-dimensional spin interactions with frustration

Agreement of computed exchange couplings with experimental data

Abstract

We present a computational study of the layered copper oxychloride [CuCl]LaNb(2)O(7) that has been recently proposed as a spin-1/2 frustrated square lattice compound. Our results evidence an orbitally degenerate ground state for the reported tetragonal crystal structure and reveal a Jahn-Teller-type structural distortion. This distortion heavily changes the local environment of copper -- CuO(2)Cl(2) plaquettes are formed instead of CuO(2)Cl(4) octahedra -- and restores the single-orbital scenario typical for copper oxides and oxyhalides. The calculated distortion is consistent with the available diffraction data and the experimental results on the electric field gradients for the Cu and Cl sites. The band structure suggests a complex three-dimensional spin model with the interactions up to the fourth neighbors. Despite the layered structure of (CuCl)LaNb(2)O(7), the spin system has pronounced one-dimensional features. Yet, sizable interchain interactions lead to the strong frustration and likely cause the spin-gap behavior. Computational estimates of individual exchange couplings are in qualitative agreement with the experimental data.