Harnessing disorder to tune, tailor and design classical and quantum spin liquids
Lead Research Organisation:
University of Oxford
Department Name: Oxford Physics
Abstract
Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.
People |
ORCID iD |
| Dharmalingam Prabhakaran (Principal Investigator) |
Publications
Behr D
(2024)
Strain-induced antiferromagnetic domain switching via the spin Jahn-Teller effect
in Physical Review B
Chen J
(2024)
Switching of ferrotoroidal domains via an intermediate mixed state in the multiferroic Y-type hexaferrite Ba 0.5 Sr 1.5 Mg 2 Fe 12 O 22
in Physical Review B
Coak M
(2024)
Magnetotransport of Sm2Ir2O7 across the pressure-induced quantum-critical phase boundary
in npj Quantum Materials
De A
(2025)
Observation of an interfacial magnon-electron drag in a pyrochlore ferromagnet-heavy metal heterostructure
in Physical Review B
Donoway E
(2024)
Multimodal Approach Reveals the Symmetry-Breaking Pathway to the Broken Helix in EuIn 2 As 2
in Physical Review X
Faure Q
(2024)
Spin dynamics and possible topological magnons in the nonstoichiometric pyrochlore iridate Tb 2 Ir 2 O 7 studied by RIXS
in Physical Review B
Lass J
(2024)
Characterizing the diffuse continuum excitations in the classical spin liquid h - YMnO 3
in Physical Review B
Luckin W
(2024)
Controlling charge density order in 2 H - TaSe 2 using a van Hove singularity
in Physical Review Research
Pearce MJ
(2022)
Magnetic monopole density and antiferromagnetic domain control in spin-ice iridates.
in Nature communications
| Description | We have successfully synthesised zirconium based pyrochlore single crystals using EPSRC funded high pressure floating zone furnace. Our collaborators has used this high quality samples and observed the disorder. Further, by doping several transition metals, we have turned the magnetism in the system. We have grown high quality pure and electron/hole doped RE2Ir2O7 and RE2Rh2O7 single crystals. Some of them are insulators, but by substituting divalent elements or applying high pressure it become conductive. This complex magnetic behavior, their highly correlated electronic states, and predictions of topological properties, make pyrochlore iridates fascinating systems for investigating exotic quantum phenomena |
| Exploitation Route | We have synthesised several frustrated magnetic materials during this project and it will be available to other groups for further studies. Based on the recent two publications, we have submitted an ERC proposal to study the domain wall migration and possible spintronics application. |
| Sectors | Education Electronics Transport |
| Description | There is a growing demand for the characterization of small single crystals, both for academic research and industrial applications in devices. Single crystals are materials with a unique orientation, resulting in anisotropic properties-where physical characteristics vary with direction. Two critical needs in single crystal research and applications are precise orientation to exploit anisotropic properties and assessment of crystalline quality (material perfection). We are applying a EPSERC grant partnership with an industry to address these challenges by developing LaueFit, a system for rapid, automated crystal alignment, incorporating predictive turnkey software. The project has two key objectives. First, to develop LaueFit software for automated crystal alignment, featuring refinement and predictive capabilities. Second, to enhance accuracy through hardware advancements, enabling market-leading precision in material alignment and outperforming competing systems. |
| First Year Of Impact | 2024 |
| Sector | Manufacturing, including Industrial Biotechology |
| Title | Empyrean powder X-ray machine |
| Description | We have installed a new Empyrean powder X-ray machine suitable for a multi-user environment where rapid materials characterisation is vital. This instrument has a high-resolution Johansson configuration to do a higher intensity mode and a parallel-beam geometry that is suitable for capillary samples. It has a latest-generation detector technology, capable to perform low and high temperature measurements. |
| Type Of Material | Improvements to research infrastructure |
| Year Produced | 2024 |
| Provided To Others? | Yes |
| Impact | This instrument plays an essential part in checking the phase purity of all our powder samples before attempting any crystal growth. |
| Title | High pressure floating zone method |
| Description | We have recently installed a piece of equipment to prepare crystals called an optical floating-zone furnace. This type of furnace uses light as a heat source reach up to 2800oC and mirrors to focus the light energy onto a bar of material in order to melt it. By scanning the molten ("floating") zone slowly along the bar one can grow a crystal as the liquid solidifies. The type of furnace is a new design of optical floating-zone furnace which allows the growth process to take place in a high pressure (up to 300 times atmospheric pressure) mixture of oxygen and argon gas. The use of a high gas pressure makes it possible to grow crystals of certain materials which cannot be grown under normal conditions. The equipment is the first of its type in Europe, to grow a broad range of materials, ranging from metal oxides that exhibit desirable magnetic, electronic and superconducting properties, through systems with novel quantum phases to materials that offer considerable promise for use in energy, optoelectronic and information storage applications. we have a programme of crystal growth with the new equipment to provide samples which will ensure the success of quantum and functional materials research in Oxford and other UK universities, and at the national research facilities such as the Diamond Light Source and ISIS Facility on the Harwell campus. |
| Type Of Material | Improvements to research infrastructure |
| Year Produced | 2021 |
| Provided To Others? | Yes |
| Impact | We have commissioned the equipment and grown several standard materials. Our crystal growth program was delayed due to COVID, but recently we have grown some new materials and studying its properties. |
| Description | Harnessing disorder to tune, tailor and design classical and quantum spin liquids |
| Organisation | Royal Holloway, University of London |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | This grant involved a collaboration project between the synthesis group here at Oxford, a neutron scattering experimental group between Royal Holloway University and the ILL facility in Grenoble France, and a condensed matter theory group at Cambridge. We are preparing samples for the collaboration, perform the crystallographic analysis and perform some preliminary measurements where relevant. In addition to this collaboration work we have also sought to prepare additional materials, both new and pre-existing with a focus on chemical and magnetic disorder. We have also begun independent magnetometry and neutron measurements, some chemically disordered pyrochlores. |
| Collaborator Contribution | My collaborators at Royal Holloway University and ILL have completed two neutron experiments to study the disorders in the Pr2ScNbO7 and Y2-xHoxTi2O7 systems and they are analyzing the recent data. They also secured a muon beam time at Canadian neutron source to study the Y2-xHoxTi2O7 system at mK temperature range. My Cambridge University collaborator is working on the theoretical modelling. |
| Impact | Cambridge collaborator has developed theoretical expertise to model and understand local spin environments and exchange interactions which are an important starting point to investigate strain and chemical substitution effects. They are working on internal fields in spin ice materials resulted in the proposal of a novel and more efficient approach to study quantum spin ice (QSI) candidate systems that they only started to explore, which provides a promising route to study the effect of disorder. In parallel, they started to investigate the role of thermal as well as quenched disorder in toy models for quantum spin liquids. Recently they have developed and tested a new numerical approach to investigate QSI in the semiclassical limit, which can be used to look at the effect of disorder and distortion on the emergent QED excitation spectrum and transport properties. My Royal Holloway collaborator is analyzing the recent experimental data and comparing the disorder with the recently developed toy model. |
| Start Year | 2020 |
| Description | Magnetic monopole density and antiferromagnetic domain control in spin-ice iridates |
| Organisation | University of Warwick |
| Department | Department of Physics |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | I have synthesised high quality Sm2Ir2O7 single crystals and characterised them in Oxford. Our Warwick collaborator measured the high pressure resistivity at different applied fields and our Cambridge collaborator developed the theoretical work to study the magnetic monopole density. |
| Collaborator Contribution | Rare-earth pyrochlore iridates host two interlocking magnetic sublattices of corner-sharing tetrahedra and can harbour a unique combination of frustrated moments, exotic excitations and highly correlated electrons. They are also the first systems predicted to display both topological Weyl semimetal and axion insulator phases. We have measured the transport and magnetotransport properties of single-crystal Sm2Ir2O7 up to and beyond the pressure-induced quantum critical point for all-in-all-out (AIAO) Ir order at p(c) = 63 kbar previously identified by resonant X-ray scattering and close to which Weyl semimetallic behavior has been previously predicted. Our findings overturn the accepted expectation that the suppression of AIAO order should lead to metallic conduction persisting down to zero temperature. Instead, the resistivity-minimum temperature, which tracks the decrease in the AIAO ordering temperature for pressures up to 30 kbar, begins to increase under further application of pressure, pointing to the presence of a second as-yet unidentified mechanism leading to non-metallic behavior. The magnetotransport does track the suppression of Ir magnetism, however, with a strong hysteresis observed only within the AIAO phase boundary, similar to that found for Ho2Ir2O7 and attributed to plastic deformation of Ir domains. Around p(c) we find the emergence of a new type of electronic phase, characterized by a negative magnetoresistance with small hysteresis at the lowest temperatures, and hysteresis-free positive magnetoresistance above approximately 5 K. The temperature dependence of our low-temperature transport data are found to be best described by a model consistent with a Weyl semimetal across the entire pressure range. |
| Impact | DOI10.1038/s41535-024-00624-8 |
| Start Year | 2021 |
| Description | Pressure-induced Quantum critical phase boundary studies in conducting pyrochlore materials |
| Organisation | University of Cambridge |
| Department | Department of Physics |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | I have synthesised high quality Sm2Ir2O7 single crystals using flux technique for the first time. This has enabled our collaborators to study the magnetotransport under high pressure to establish the quantum critical phase boundary. |
| Collaborator Contribution | Rare-earth pyrochlore iridates host two interlocking magnetic sublattices of corner-sharing tetrahedra and can harbour a unique combination of frustrated moments, exotic excitations and highly correlated electrons. They are also the first systems predicted to display both topological Weyl semimetal and axion insulator phases. Our experimental collaborators have measured the transport and magnetotransport properties of single-crystal Sm2Ir2O7 up to and beyond the pressure-induced quantum critical point for all-in-all-out (AIAO) Ir order at pc = 63 kbar previously identified by resonant X-ray scattering and close to which Weyl semimetallic behavior has been previously predicted. Our theory collaborators from University of Cambridge has performed the crystal-field calculations. |
| Impact | Based on this work, we have submitted an ERC proposal in collaboration with Cambridge University theory group. |
| Start Year | 2023 |
| Description | Pressure-induced Quantum critical phase boundary studies in conducting pyrochlore materials |
| Organisation | University of Warwick |
| Department | Department of Physics |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | I have synthesised high quality Sm2Ir2O7 single crystals using flux technique for the first time. This has enabled our collaborators to study the magnetotransport under high pressure to establish the quantum critical phase boundary. |
| Collaborator Contribution | Rare-earth pyrochlore iridates host two interlocking magnetic sublattices of corner-sharing tetrahedra and can harbour a unique combination of frustrated moments, exotic excitations and highly correlated electrons. They are also the first systems predicted to display both topological Weyl semimetal and axion insulator phases. Our experimental collaborators have measured the transport and magnetotransport properties of single-crystal Sm2Ir2O7 up to and beyond the pressure-induced quantum critical point for all-in-all-out (AIAO) Ir order at pc = 63 kbar previously identified by resonant X-ray scattering and close to which Weyl semimetallic behavior has been previously predicted. Our theory collaborators from University of Cambridge has performed the crystal-field calculations. |
| Impact | Based on this work, we have submitted an ERC proposal in collaboration with Cambridge University theory group. |
| Start Year | 2023 |
| Description | Tuning complex orbital ordering and excitonic magnetism |
| Organisation | University of Edinburgh |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | Grow high quality crystals incorporating 3d transition metal ions with orbital degeneracy, on a scale appropriate for experiments using high pressure floating zone, flux and chemical vapour transport. |
| Collaborator Contribution | University of Edinburgh group is working on the characterisation methodologies for neutron spectroscopy. They also apply scattering to tune phases and connect magnetic and stricture properties in single crystals. University of Glasgow is developing the electromechanical resonant techniques to improve the acoustic sound fluctuation techniques thereby connecting neutron THz frequency scales with lower frequencies relevant for critical behaviour of new phases and applications. |
| Impact | Recently we have performed a neutron scattering measurement on a high quality single crystal which was grown in Oxford. Our Edinburgh collaborators are analysing the data now. |
| Start Year | 2023 |
| Description | New materials discovery using high pressure floating-zone furnace |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Industry/Business |
| Results and Impact | I have introduced the recently installed EPSRC funded 300bar high pressure floating-zone furnace capabilities at the American Crystal Growth meeting. It was well received by the industrial representatives and general public. |
| Year(s) Of Engagement Activity | 2021 |