Vacancy defects and monopole dynamics in oxygen-deficient pyrochlores

G. Sala; M. J. Gutmann; D. Prabhakaran; D. Pomaranski; C. Mitchelitis; J. B. Kycia; D. G. Porter; C. Castelnovo; J. P. Goff

doi:10.1038/nmat3924

Vacancy defects and monopole dynamics in oxygen-deficient pyrochlores

G. Sala, M. J. Gutmann, D. Prabhakaran, D. Pomaranski, C. Mitchelitis, J. B. Kycia, D. G. Porter, C. Castelnovo, J. P. Goff

Research output: Contribution to journal › Article › peer-review

85 Scopus citations

Abstract

The idea of magnetic monopoles in spin ice has enjoyed much success at intermediate temperatures, but at low temperatures a description in terms of monopole dynamics alone is insufficient. Recently, numerical simulations were used to argue that magnetic impurities account for this discrepancy by introducing a magnetic equivalent of residual resistance in the system. Here we propose that oxygen deficiency is the leading cause of magnetic impurities in as-grown samples, and we determine the defect structure and magnetism in Y 2 Ti 2 O 7 using diffuse neutron scattering and magnetization measurements. These defects are eliminated by oxygen annealing. The introduction of oxygen vacancies causes Ti 4+ to transform to magnetic Ti 3+ with quenched orbital magnetism, but the concentration is anomalously low. In the spin-ice material Dy 2 Ti 2 O 7 we find that the same oxygen-vacancy defects suppress moments on neighbouring rare-earth sites, and that these magnetic distortions markedly slow down the long-time monopole dynamics at sub-Kelvin temperatures.

Original language	English
Pages (from-to)	488-493
Number of pages	6
Journal	Nature Materials
Volume	13
Issue number	5
DOIs	https://doi.org/10.1038/nmat3924
State	Published - May 2014
Externally published	Yes

Funding

We thank M. Jura and T. Lehner for their help, and B. Gaulin, M. T. Hutchings, K. Refson, R. Moessner, S. L. Sondi, S. Dutton and U. Karahasanovic for helpful discussions. We acknowledge support from the South East Physics Network and the Hubbard Theory Consortium, and we are grateful for the financial support and hospitality of ISIS. This work was supported in part by EPSRC grants EP/G049394/1, EP/H033939/1 and EP/K028960/1, NSERC, the Helmholtz Virtual Institute ‘New States of Matter and Their Excitations’, and the EPSRC NetworkPlus on ‘Emergence and Physics far from Equilibrium’.

Funders	Funder number
Hubbard Theory Consortium
ISIS
South East Physics Network
Natural Sciences and Engineering Research Council of Canada
Engineering and Physical Sciences Research Council	EP/G049394/1, EP/H033939/1, EP/J011150/1, EP/K028960/1

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abstract = "The idea of magnetic monopoles in spin ice has enjoyed much success at intermediate temperatures, but at low temperatures a description in terms of monopole dynamics alone is insufficient. Recently, numerical simulations were used to argue that magnetic impurities account for this discrepancy by introducing a magnetic equivalent of residual resistance in the system. Here we propose that oxygen deficiency is the leading cause of magnetic impurities in as-grown samples, and we determine the defect structure and magnetism in Y 2 Ti 2 O 7 using diffuse neutron scattering and magnetization measurements. These defects are eliminated by oxygen annealing. The introduction of oxygen vacancies causes Ti 4+ to transform to magnetic Ti 3+ with quenched orbital magnetism, but the concentration is anomalously low. In the spin-ice material Dy 2 Ti 2 O 7 we find that the same oxygen-vacancy defects suppress moments on neighbouring rare-earth sites, and that these magnetic distortions markedly slow down the long-time monopole dynamics at sub-Kelvin temperatures.",

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AU - Sala, G.

AU - Gutmann, M. J.

AU - Prabhakaran, D.

AU - Pomaranski, D.

AU - Mitchelitis, C.

AU - Kycia, J. B.

AU - Porter, D. G.

AU - Castelnovo, C.

AU - Goff, J. P.

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Vacancy defects and monopole dynamics in oxygen-deficient pyrochlores

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