Stability of Ferromagnetism and Ferromagnetic Orbital Selective Mott Phase in Three-Orbital Hubbard Model

In this paper we investigate the nature of ferromagnetic (FM) phase in three-orbital Hubbard model by using Kotliar-Ruckenstein slave-boson approach. We find that the FM metallic phase widely exists and stabilizes in magnetic phase diagram for large Hund’s rule coupling, and FM insulator is not seen. An FM orbital-selective Mott phase (OSMP), mainly due to large crystal field splitting and strong electronic correlation, is observed and identified as double-exchange FM. An antiferromagnetic (AFM) OSMP is also found. We conclude that large Coulomb correlation and Hund’s rule coupling is crucial for stable FM phase, and further crystal field splitting also enhance the stability of AFM and FM OSMP.