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

A 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 a 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 an external magnetic field to a different one accompanied by the formation of a half-magnetization plateau.