Crystal growth, structure and magnetic properties of Ca10Cr7O28

TL;DR

This study provides a comprehensive structural and magnetic analysis of Ca10Cr7O28, revealing a new crystal structure, valence states, and magnetic ion arrangements, which underpin its quantum spin liquid behavior.

Contribution

It introduces a new crystal structure model with doubled axes and clarifies the valence and magnetic site distribution in Ca10Cr7O28.

Findings

Identified a new crystal structure with doubled axes.

Confirmed presence of Cr5+ and Cr6+ valence states.

Discovered Cr5+ ions form distorted kagome bilayers.

Abstract

A detailed diffraction study of Ca10Cr7O28 is presented which adds significant new insights into the structural and magnetic properties of this compound. A new crystal structure type was used where the a and b axes are doubled compared to previous models providing a more plausible structure where all crystallographic sites are fully occupied. The presence of two different valences of chromium was verified and the locations of the magnetic Cr5+ and non-magnetic Cr6+ ions were identified. The Cr5+ ions have spin-1/2 and form distorted kagome bilayers which are stacked in an ABC arrangement along the c axis. These results lay the foundation for understanding of the quantum spin liquid behavior in Ca10Cr7O28 which has recently been reported in [C. Balz et al., Nature Physics, 12, 942 (2016)].