The spin-1/2 Heisenberg ferromagnet on the pyrochlore lattice: A Green's function study

Abstract

We consider the pyrochlore-lattice quantum Heisenberg ferromagnet and discuss the properties of this spin model at arbitrary temperatures. To this end, we use the Green's function technique within the random-phase (or Tyablikov) approximation as well as the linear spin-wave theory and quantum Monte Carlo simulations. We compare our results to the ones obtained recently by other methods to corroborate our 1ndings. Finally, we contrast our results with the ones for the simple-cubic-lattice case: both lattices are identical at the mean-1eld level. We demonstrate that thermal 2uctuations are more eWcient in the pyrochlore case (1nite-temperature frustration effects). Our results may be of use for interpreting experimental data for ferromagnetic pyrochlore materials.