Origin of the intermediate-temperature magnetic specific heat capacity in the spin-liquid candidate Ca$_{10}$Cr$_7$O$_{28}$

TL;DR

This paper investigates the specific heat capacity of the spin-liquid candidate Ca$_{10}$Cr$_7$O$_{28}$ using various theoretical methods, but fails to match experimental data, suggesting the need for revised models of its magnetic properties.

Contribution

The study applies multiple computational approaches to model the specific heat of Ca$_{10}$Cr$_7$O$_{28}$ and highlights discrepancies with experimental results, indicating potential inaccuracies in the current magnetic Hamiltonian.

Findings

Exact diagonalization and other methods do not reproduce experimental specific heat.

Discrepancies suggest the magnetic Hamiltonian may need revision.

Discussion of possible reasons for the mismatch.

Abstract

We present several approximate calculations of the specific heat capacity of the model for Ca$_{10}$Cr$_7$O$_{28}$ proposed by Balz et al. [Phys. Rev. B 95, 174414 (2017)], using methods including exact diagonalization, Thermal Pure Quantum States, and high-temperature expansions. In none of these cases are we able to reproduce the magnitude of the zero-field specific heat capacity shown in the intermediate-temperature $({\sim}\,5-15\,\rm{K})$ experimental data. We discuss possible reasons for the discrepancy, and what it might tell us about the magnetic Hamiltonian for Ca$_{10}$Cr$_7$O$_{28}$.