Magnetocaloric effect and magnetic cooling near a field-induced quantum-critical point

TL;DR

This study investigates the magnetocaloric effect near a field-induced quantum critical point in a spin-1/2 antiferromagnetic chain, demonstrating potential for efficient low-temperature magnetic cooling through entropy accumulation.

Contribution

It provides the first combined experimental and theoretical analysis of the magnetocaloric effect near a quantum critical point in a spin chain system.

Findings

Enhanced magnetocaloric effect near the QCP

Effective low-temperature magnetic cooling demonstrated

Correlation between entropy accumulation and cooling efficiency

Abstract

The presence of a quantum critical point (QCP) can significantly affect the thermodynamic properties of a material at finite temperatures T. This is reflected, e.g., in the entropy landscape S(T, r) in the vicinity of a QCP, yielding particularly strong variations for varying the tuning parameter r such as pressure or magnetic field B. Here we report on the determination of the critical enhancement of $ \delta S / \delta B$ near a B-induced QCP via absolute measurements of the magnetocaloric effect (MCE), $(\delta T / \delta B)_S$, and demonstrate that the accumulation of entropy around the QCP can be used for efficient low-temperature magnetic cooling. Our proof of principle is based on measurements and theoretical calculations of the MCE and the cooling performance for a Cu$^{2+}$-containing coordination polymer, which is a very good realization of a spin-1/2 antiferromagnetic Heisenberg chain - one of the simplest quantum-critical systems.