Giant magnetocaloric effect in Cr-based two-dimensional materials

Abstract

The rise of two-dimensional magnets offers a broad research platform for exploring low-dimensional magnetocaloric technology for efficient and green refrigeration applications. Here, we focus on a two-dimensional ferromagnetic semiconductor CrSX (X = F, Cl, Br, I) to investigate its magnetocaloric properties and thermal transport properties along with the underlying physical mechanisms. It is found that CrSX intrinsically possesses a substantial isothermal entropy change (−ΔSmagmax) of 12.3 μJ m−2 K−1 and adiabatic temperature change (ΔTadmax) of 2.3 K during magnetic phase transition. Surprisingly, it exhibits remarkably high thermal conductivity of up to 54.47 W/mK that is attributed to the extended phonon lifetime. Additionally, tensile strain effectively modulates the Curie temperature and refrigerant capacity, with tensile strain weakening direct antiferromagnetic coupling, thus enhancing ferromagnetism. Hole doping efficiently adjusts the magnetic exchange interaction, which enhances the Curie temperature of CrSI to room temperature (305 K) while maintaining a high refrigerant capacity of 180 J/mol under a magnetic field, ascribing to the reduced energy gap between eg orbitals of transition metal cations and p orbitals of nonmagnetic anions. The present work provides insights for understanding the relation between magnetic exchange interactions, thermal transport, and refrigerant performance, offering guidance for designing two-dimensional magnets for magnetocaloric applications.