First-principles discovery of half-metallicity in lead-free CsBCl3(B = Ti, V, Cr) halide perovskites for spintronic and spin-dependent applications

Abstract

We employ density functional theory (DFT) combined with Monte Carlo simulations to investigate the structural, electronic, magnetic, and mechanical properties of lead-free halide perovskites CsBCl${}_3$ (B = Ti, V, Cr). Our findings reveal that CsTiCl${}_3$ and CsCrCl${}_3$ exhibit half-metallic ferromagnetism with wide spin-down band gaps and 100% spin polarization, making them promising candidates for spintronic applications. In contrast, CsVCl${}_3$ stabilizes in an antiferromagnetic semiconducting ground state with a band gap of 3.03 eV (GGA+U), indicating potential for optoelectronic use. By mapping exchange interactions from first-principles onto a classical Heisenberg model and performing Monte Carlo simulations, we estimate Curie temperatures of approximately 200 K and 240 K for CsTiCl${}_3$ and CsCrCl${}_3$, respectively, confirming their finite-temperature magnetic stability. Among them, CsCrCl${}_3$ exhibits the strongest magnetic exchange, highest $T_C$, and notable mechanical resilience (bulk modulus = 34.51 GPa, Pugh’s ratio = 1.76), underscoring its suitability for moderate-temperature spintronic applications. Phonon dispersion analyses confirm the dynamical stability of all three compounds in their cubic phase.