Crystal water induced switching of magnetically active orbitals in CuCl2

TL;DR

This study uncovers how crystal water removal from CuCl2 causes a switch in magnetically active orbitals, fundamentally altering its magnetic ground state from 3D antiferromagnetic to quasi-1D behavior, with implications for magnetic material design.

Contribution

It reveals the microscopic mechanism behind water-driven orbital switching in CuCl2, combining experimental thermodynamics and electronic structure calculations.

Findings

Dehydration changes magnetic behavior from 3D to quasi-1D.

CuCl2 modeled as a frustrated J1-J2 Heisenberg chain.

Predicted helical ground state due to ferromagnetic J1 and J2/J1 ~ -1.5.

Abstract

The dehydration of CuCl2*2(H2O) to CuCl2 leads to a dramatic change in magnetic behavior and ground state. Combining density functional electronic structure and model calculations with thermodynamical measurements we reveal the microscopic origin of this unexpected incident -- a crystal water driven switching of the magnetically active orbitals. This switching results in a fundamental change of the coupling regime from a three-dimensional antiferromagnet to a quasi one-dimensional behavior. CuCl2 can be well described as a frustrated J1-J2 Heisenberg chain with ferromagnetic exchange J1 and J2/J1 ~ -1.5 for which a helical ground state is predicted.