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- Title
Zero-point entropy in stuffed spin-ice.
- Authors
Lau, G. C.; Freitas, R. S.; Ueland, B. G.; Muegge, B. D.; Duncan, E. L.; Schiffer, P.; Cava, R. J.
- Abstract
The third law of thermodynamics dictates that the entropy of a system in thermal equilibrium goes to zero as its temperature approaches absolute zero. In ice, however, a ‘zero point’ or residual entropy can be measured—attributable to a high degeneracy in the energetically preferred positions of hydrogen ions associated with the so-called ‘ice rules’. Remarkably, the spins in certain magnetic materials with the pyrochlore structure of corner-sharing tetrahedra, called ‘spin ice’, have an equivalent degeneracy of energetically preferred states, and also have a zero-point entropy. Here, we chemically alter Ho2Ti2O7 spin ice by ‘stuffing’ extra Ho magnetic moments into otherwise non-magnetic Ti sites surrounding the Ho tetrahedra. The resulting series, Ho2(Ti2−xHox)O7−x/2, provides a unique opportunity to study the effects of increased connectivity between spins on a frustrated lattice. Surprisingly, the zero-point entropy per spin measured appears unchanged by these excess spins. The results suggest a chemical approach for studying ice-like frustration and other properties of the broad family of geometrically frustrated magnets based on the pyrochlore structure.
- Subjects
THERMODYNAMICS; ENTROPY; PHYSICS; MAGNETISM; LATTICE theory
- Publication
Nature Physics, 2006, Vol 2, Issue 4, p249
- ISSN
1745-2473
- Publication type
Article
- DOI
10.1038/nphys270