Mechanically Strong and Room-Temperature Magnetocaloric Monolayer VSi2N4 Semiconductor

Abstract

In the realm of emerging two-dimensional MoSi2N4 family, the majority of research endeavors gravitate towards their versatile physical properties, while their magnetocalotic effect (MCE) for the potential refrigeration application remains uncharted. Here, we comprehensively explore the magnetic, electronic, mechanical, and magnetocaloric properties of monolayer VA2Z4 (A=Si, Ge; Z=N, P, As) family by multiscale simulations, revealing that monolayer VSi2N4 semiconductor is mechanically strong and exhibits room-temperature MCE. The nonlinear elastic response of VSi2N4 unveils strong mechanical properties, featuring a substantial in-plane Young’s modulus (E2D ∼ 350 N/m) and a high strength of 40.8 N/m, comparable to that of graphene. MCE of VA2Z4 encompasses the working temperature from low to room temperature (78–318 K). Specifically, room-temperature MCE of monolayer VSi2N4 exhibits a maximum magnetic entropy change (−∆SMmax) of 2.82 µJ m−2 K−1, a maximum adiabatic temperature change (∆Tadmax) of 0.37 K, and a relative cooling power of 313 µJ m−2 under a magnetic field of 5 T. Moreover, applying biaxial strain can significantly improve −∆SMmax and ∆Tadmax in VSi2N4 by 80.9% and 197.3%, respectively. Room-temperature MCE with wide working temperature and mechanical robustness make monolayer VSi2N4 as an appealing candidate for magnetic refrigeration applications over large temperature range. These findings offer new insights for advancing the development of magnetic cooling in small-sized systems.

Keywords: Monolayer magnets, Magnetocaloric effect, Nonlinear elasticity, Mechanical strength, Entropy