Abstract
The pyrochlore spin ice compounds and are well described by classical Ising models down to low temperatures. Given the empirical success of this description, the question of the importance of quantum effects in these materials has been mostly ignored. We show that the common wisdom that the strictly Ising moments of isolated and ions imply Ising interactions is too naïve; a more complex argument is needed to explain the close agreement between theory and experiment. From a microscopic picture of the interactions in rare-earth oxides, we show that the high-rank multipolar interactions needed to induce quantum effects in these two materials are generated only very weakly by superexchange. Using this framework, we formulate an estimate of the scale of quantum effects in and , finding it to be well below experimentally relevant temperatures. We discuss the implications of these results for realizing quantum spin ice in other materials.
- Received 20 March 2015
- Revised 11 September 2015
DOI:https://doi.org/10.1103/PhysRevB.92.144417
©2015 American Physical Society