Journal
NATURE MATERIALS
Volume 13, Issue 5, Pages 488-493Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/NMAT3924
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Funding
- South East Physics Network
- Hubbard Theory Consortium
- ISIS
- EPSRC [EP/G049394/1, EP/H033939/1, EP/K028960/1]
- NSERC
- Helmholtz Virtual Institute 'New States of Matter and Their Excitations'
- EPSRC NetworkPlus on 'Emergence and Physics far from Equilibrium'
- Engineering and Physical Sciences Research Council [EP/J011150/1, EP/K028960/1, EP/H033939/1] Funding Source: researchfish
- EPSRC [EP/K028960/1, EP/H033939/1, EP/J011150/1] Funding Source: UKRI
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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 insuffcient. 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 Y2Ti2O7-delta using diffuse neutron scattering and magnetization measurements. These defects are eliminated by oxygen annealing. The introduction of oxygen vacancies causes Ti4+ to transform to magnetic Ti3+ with quenched orbital magnetism, but the concentration is anomalously low. In the spin-ice material Dy2Ti2O7 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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