Magnetic phase diagram of a five-orbital Hubbard model in the real-space Hartree-Fock approximation varying the electronic density

摘要

Using the real-space Hartree-Fock approximation, the magnetic phase diagram of a five-orbital Hubbard model for the iron-based superconductors is studied varying the electronic density n in the range from five to seven electrons per transition metal atom. The Hubbard interaction U is also varied, at a fixed Hund coupling J/U = 0.25. Several qualitative trends and a variety of competing magnetic states are observed. At n = 5, a robust G-type antiferromagnetic insulator is found, in agreement with experimental results for BaMn_2As_2). As n increases away from 5, magnetic states with an increasing number of nearest-neighbors ferromagnetic links become energetically stable. This includes the well-known C-type antiferromagnetic state at n - 6, the E-phase known to exist in FeTe, and also a variety of novel states not found yet experimentally, some of them involving blocks of ferromagnetically oriented spins. Regions of phase separation, as in Mn oxides, have also been detected. Comparison to previous theoretical investigations indicate that these qualitative trends may be generic characteristics of phase diagrams of multi-orbital Hubbard models.