Interplay between lattice, orbital, and magnetic degrees of freedom in the chain-polymer Cu(II) breathing crystals

TL;DR

This study investigates how structural changes at 146 K in Cu(II) breathing crystals influence orbital order and magnetic interactions, revealing a link between lattice, orbital, and magnetic degrees of freedom.

Contribution

It demonstrates the temperature-induced structural transition causes orbital reordering and switches magnetic interaction signs in Cu(II) breathing crystals.

Findings

Structural transition at 146 K affects orbital order.

Orbital reordering leads to magnetic interaction sign change.

Magnetic behavior aligns with Goodenough-Kanamori-Andersen theory.

Abstract

The chain-polymer Cu(II) breathing crystals C21H19CuF12N4O6 were studied using the x-ray diffraction and ab initio band structure calculations. We show that the crystal structure modification at T=146 K, associated with the spin crossover transition, induces the changes of the orbital order in half of the Cu sites. This in turn results in the switch of the magnetic interaction sign in accordance with the Goodenough-Kanamori-Andersen theory of the coupling between the orbital and spin degrees of freedom.