Monte Carlo studies of the dipolar spin ice model

Abstract

We present a detailed theoretical overview of the thermodynamic properties of\nthe dipolar spin ice model, which has been shown to be an excellent\nquantitative descriptor of the Ising pyrochlore materials Dy_2Ti_2O_7 and\nHo_2Ti_2O_7. We show that the dipolar spin ice model can reproduce an effective\nquasi macroscopically degenerate ground state and spin-ice behavior of these\nmaterials when the long-range nature of dipole-dipole interaction is handled\ncarefully using Ewald summation techniques. This degeneracy is, however,\nultimately lifted at low temperature. The long-range ordered state is\nidentified via mean field theory and Monte Carlo simulation techniques.\nFinally, we investigate the behavior of the dipolar spin ice model in an\napplied magnetic field, and compare our predictions with experimental results.\nWe find that a number of different long-range ordered states are favored by the\nmodel depending on field direction.\n