Magnetic Phase-Transition Engineering in Fe2P-Type Magnetocaloric Alloys: Multiscale Theoretical Insights

Fe2P-type alloys exhibit strong magnetostructural coupling and tunable magnetic transitions,making them promising magnetocaloric materials. However, achieving a large magnetic entropy change (-∆Sm) while maintaining low thermal hysteresis (∆Thys) near room temperature remains a challenge. Here, we employ multiscale theoretical calculations combining density functional theory (DFT), Monte Carlo simulations, mean-field modeling, and Landau expansion theory to investigate the composition-dependent structural, magnetic, and magnetocaloric properties of MnxFe2-xP1-ySiy alloys. Our calculations show that Mn and Si enrichment stabilizes the hexagonal phase and reduces the c/a ratio, leading to enhanced magnetization and a Curie temperature closer to room temperature. Furthermore, Mn- and Si-rich compositions (x>1 and y>0.5) approach second-order-like magnetic transition behavior, accompanied by more continuous magnetization and suppressed hysteresis. This transition regime is predicted to realize the coexistence of a large magnetic entropy change and low thermal hysteresis, demonstrating that magnetic phase-transition engineering provides adesign principle for high-performance Fe2P-type magnetocaloric materials.