Restoration of the third law in spin ice thin films

L Bovo; X Moya; D Prabhakaran; Yeong-Ah Soh; A T Boothroyd; N D Mathur; G Aeppli; S T Bramwell

doi:10.1038/ncomms4439

Restoration of the third law in spin ice thin films

Nat Commun. 2014 Mar 12:5:3439. doi: 10.1038/ncomms4439.

Authors

L Bovo¹, X Moya², D Prabhakaran³, Yeong-Ah Soh⁴, A T Boothroyd³, N D Mathur², G Aeppli¹, S T Bramwell¹

Affiliations

¹ London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, 17-19 Gordon Street, London WC1H OAH, UK.
² Department of Materials Science, University of Cambridge, Cambridge CB2 3QZ, UK.
³ Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, UK.
⁴ 1] London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, 17-19 Gordon Street, London WC1H OAH, UK [2] Department of Materials, Imperial College London, Prince Consort Rd, London SW7 2BP, UK.

Abstract

A characteristic feature of spin ice is its apparent violation of the third law of thermodynamics. This leads to a number of interesting properties including the emergence of an effective vacuum for magnetic monopoles and their currents - magnetricity. Here we add a new dimension to the experimental study of spin ice by fabricating thin epitaxial films of Dy2Ti2O7, varying between 5 and 60 monolayers on an inert substrate. The films show the distinctive characteristics of spin ice at temperatures >2 K, but at lower temperature we find evidence of a zero entropy state. This restoration of the third law in spin ice thin films is consistent with a predicted strain-induced ordering of a very unusual type, previously discussed for analogous electrical systems. Our results show how the physics of frustrated pyrochlore magnets such as spin ice may be significantly modified in thin-film samples.

Publication types

Research Support, Non-U.S. Gov't