Magnetic Order and Charge Disproportionation in a Spin-ice type Kondo Lattice Model: Large Scale Monte Carlo Study

Phase diagram of a spin-ice type Kondo lattice model, potentially relevant to metallic pyrochlore oxides, is obtained by the Monte Carlo simulation implementing the polynomial expansion technique up to the system size with 2048 sites. We identified a new 32-sublattice magnetic phase with concomitant charge disproportionation, along with other phases such as two-in two-out and all-in/all-out orders. The spin and charge pattern can be switched by external magnetic field to a different one accompanied by a half magnetization plateau.