Giant magnetocaloric effect in magnets down to the monolayer limit

TL;DR

This study predicts giant magnetocaloric effects in monolayer magnets like CrX3 and Fe3GeTe2, with strain tuning significantly enhancing their cooling capabilities, opening new avenues for nanoscale magnetic cooling technologies.

Contribution

The paper demonstrates, through multiscale calculations, the existence of giant and strain-tunable magnetocaloric effects in monolayer magnets, a previously unexplored area.

Findings

Max adiabatic temperature change up to 11 K in CrF3

Strain increases MCE in CrCl3 and CrOF by over 200%

Large magnetic moments enhance magnetocaloric effect

Abstract

Two-dimensional magnets could potentially revolutionize information technology, but their potential application to cooling technology and magnetocaloric effect (MCE) in a material down to the monolayer limit remain unexplored. Herein, we reveal through multiscale calculations the existence of giant MCE and its strain tunability in monolayer magnets such as CrX$_3$ (X=F, Cl, Br, I), CrAX (A=O, S, Se; X=F, Cl, Br, I), and Fe$_3$GeTe$_2$. The maximum adiabatic temperature change ($\Delta T_\text{ad}^\text{max}$), maximum isothermal magnetic entropy change, and specific cooling power in monolayer CrF$_3$ are found as high as 11 K, 35 $\mu$Jm$^{-2}$K$^{-1}$, and 3.5 nWcm$^{-2}$ under a magnetic field of 5 T, respectively. A 2% biaxial and 5% $a$-axis uniaxial compressive strain can remarkably increase $\Delta T_\text{ad}^\text{max}$ of CrCl$_3$ and CrOF by 230% and 37% (up to 15.3 and 6.0 K), respectively. It is found that large net magnetic moment per unit area favors improved MCE. These findings advocate the giant-MCE monolayer magnets, opening new opportunities for magnetic cooling at nanoscale.