Ising pyrochlore magnets: Low temperature properties, ice rules and beyond

TL;DR

This paper investigates the low-temperature magnetic behaviors of pyrochlore magnets, revealing three distinct states influenced by competing interactions, and clarifies the specific behavior of Ho2Ti2O7 as a partially ordered system.

Contribution

It provides a theoretical framework and experimental validation for understanding diverse magnetic states in R2Ti2O7 pyrochlores, including the novel identification of Ho2Ti2O7 as a partially ordered state.

Findings

Identified three distinct magnetic behaviors driven by interactions.

Revealed Ho2Ti2O7 corresponds to a partially ordered state.

Showed behavior differs from conventional spin ice models.

Abstract

Pyrochlore magnets are candidates for spin-ice behavior. We present theoretical simulations of relevance for the pyrochlore family R2Ti2O7 (R= rare earth) supported by magnetothermal measurements on selected systems. By considering long ranged dipole-dipole as well as short-ranged superexchange interactions we get three distinct behaviours: (i) an ordered doubly degenerate state, (ii) a highly disordered state with a broad transition to paramagnetism, (iii) a partially ordered state with a sharp transition to paramagnetism. Thus these competing interactions can induce behaviour very different from conventional ``spin ice''. Closely corresponding behaviour is seen in the real compounds---in particular Ho2Ti2O7 corresponds to case (iii) which has not been discussed before, rather than (ii) as suggested earlier.