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- Edberg, Richard, et al.
(författare)
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Dipolar spin ice under uniaxial pressure
- 2019
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 100:14
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Tidskriftsartikel (refereegranskat)abstract
- The magnetically frustrated spin ice family of materials is host to numerous exotic phenomena such as magnetic monopole excitations and macroscopic residual entropy extending to low temperature. A finite-temperature ordering transition in the absence of applied fields has not been experimentally observed in the classical spin ice materials Dy2Ti2O7 and Ho2Ti2O7. Such a transition could be induced by the application of pressure, and in this work we consider the effects of uniaxial pressure on classical spin ice systems. Theoretically, we find that the pressure-induced ordering transition in Dy2Ti2O7 is strongly affected by the dipolar interaction. We also report measurements of the neutron structure factor of Ho2Ti2O7 under pressure and compare the experimental results to the predictions of our theoretical model.
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| 4. |
- Edberg, Richard, et al.
(författare)
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Effects of uniaxial pressure on the spin ice Ho2Ti2O7
- 2020
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 102:18
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Tidskriftsartikel (refereegranskat)abstract
- The spin ice materials Ho2Ti2O7 and Dy2Ti2O7 are experimental and theoretical exemplars of highly frustrated magnetic materials. However, the effects of applied uniaxial pressure are not well studied, and here we report magnetization measurements of Ho2Ti2O7 under uniaxial pressure applied in the [001], [111], and [110] crystalline directions. The basic features are captured by an extension of the dipolar spin ice model. We find a good match between our model and measurements with pressures applied along two of the three directions, and we extend the framework to discuss the influence of crystal misalignment for the third direction. The parameters determined from the magnetization measurements reproduce neutron scattering measurements that we perform under uniaxial pressure applied along the [110] crystalline direction. In the detailed analysis, we include the recently verified susceptibility dependence of the demagnetizing factor. Our work demonstrates the application of a moderate applied pressure to modify the magnetic interaction parameters. The knowledge can be used to predict critical pressures needed to induce new phases and transitions in frustrated materials, and in the case of Ho2Ti2O7 we expect a transition to a ferromagnetic ground state for uniaxial pressures above 3.3 GPa.
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- Sandberg, L. o., et al.
(författare)
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Design, calibration, and performance of a uniaxial pressure cell for neutron scattering studies of quantum magnetism
- 2023
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 94:10
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Tidskriftsartikel (refereegranskat)abstract
- We provide an overview of a pressure cell designed to apply uniaxial pressure to single crystals for the study, by neutron scattering techniques, of strongly correlated magnetic systems and, in particular, quantum magnets. A detailed overview of the pressure cell components, their requirements, and links to the scientific and technical specifications are presented. The pressure cell is able to accommodate a 200 mm(3) single crystal that can be pressurized up to 2 GPa at cryogenic temperatures. The pressure cell is consistent with the requirements of inelastic neutron scattering and, importantly, neutron polarization analysis. A particular strength of the uniaxial pressure cell is the highly uniform and low background for a wide scattering angle of 360(degrees) horizontally and +/- 20(degrees) vertically. We show the performance of the uniaxial pressure cell using a relevant neutron scattering instrument, the polarized diffuse scattering instrument, D7. The experiments confirm that the cell complies with the scientific and technical requirements. This uniaxial pressure cell will provide a useful additional tool in the sample environment suite available for the study of quantum magnetism.
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- Gendreau, R. Michael, et al.
(författare)
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Self-guided digital behavioural therapy versus active control for fibromyalgia (PROSPER-FM) : a phase 3, multicentre, randomised controlled trial
- 2024
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Ingår i: The Lancet. - : Elsevier. - 0140-6736 .- 1474-547X. ; 404:10450, s. 364-374
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Tidskriftsartikel (refereegranskat)abstract
- Background International guidelines have recommended cognitive behavioural therapy, including acceptance and commitment therapy (ACT), as it offers validated benefits for managing fibromyalgia; however, it is inaccessible to most patients. We aimed to evaluate the effect of a 12-week, self-guided, smartphone-delivered digital ACT programme on fibromyalgia management. Methods In the PROSPER-FM randomised clinical trial conducted at 25 US community sites, adult participants aged 22-75 years with fibromyalgia were recruited and randomly assigned (1:1) to the digital ACT group or an active control group that offered daily symptom tracking and monitoring and access to health-related and fibromyalgiarelated educational materials. Randomisation was done with a web-based system in permuted blocks of four at the site level. We used a blind-to-hypothesis approach in which participants were informed they would be randomly assigned to one of two potentially effective therapies under evaluation. Research staff were not masked to group allocation, with the exception of a masked statistics group while preparing statistical programming for the interim analysis. The primary endpoint was patient global impression of change (PGIC) response rate at week 12. Analyses were by intention to treat. The trial was registered with ClinicalTrials.gov, NCT05243511 (now fully closed). Findings Between Feb 8, 2022, and Feb 2, 2023, 590 individuals were screened, of whom 275 (257 women and 18 men) were randomly assigned to the digital ACT group (n=140) and the active control group (n=135). At 12 weeks, 99 (71%) of 140 ACT participants reported improvement on PGIC versus 30 (22%) of 135 active control participants, corresponding to a difference in proportions of 484% (95% CI 379-589; p<00001). No device-related safety events were reported. Interpretation Digital ACT was safe and efficacious compared with digital symptom tracking in managing fibromyalgia in adult patients. Copyright (c) 2024 Elsevier Ltd. All rights reserved, including those for text and data mining, AI training, and similar technologies.
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- Guthrie, M., et al.
(författare)
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Thermal expansion in UO2 determined by high-energy X-ray diffraction
- 2016
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115. ; 479, s. 19-22
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Tidskriftsartikel (refereegranskat)abstract
- Here we present crystallographic analyses of high-energy X-ray diffraction data on polycrystalline UO2 up to the melting temperature. The Rietveld refinements of our X-ray data are in agreement with previous measurements, but are systematically located around the upper bound of their uncertainty, indicating a slightly steeper trend of thermal expansion compared to established values. This observation is consistent with recent first principles calculations.
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