A5032382798- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- Multiferroics and related materials
- Magnetic and transport properties of perovskites and related materials
- Nuclear materials and radiation effects
- Rare-earth and actinide compounds
- Iron-based superconductors research
- Theoretical and Computational Physics
- High-pressure geophysics and materials
- Ferroelectric and Piezoelectric Materials
- Crystal Structures and Properties
- Atomic and Subatomic Physics Research
- Inorganic Fluorides and Related Compounds
- Magnetism in coordination complexes
- Topological Materials and Phenomena
- Advanced Chemical Physics Studies
- Magneto-Optical Properties and Applications
- Acoustic Wave Resonator Technologies
- Magnetic properties of thin films
- Lanthanide and Transition Metal Complexes
- Inorganic Chemistry and Materials
- Quantum, superfluid, helium dynamics
- Quantum many-body systems
- Electronic and Structural Properties of Oxides
- Adhesion, Friction, and Surface Interactions
Paul Scherrer Institute
2015-2024
Institut Laue-Langevin
2009-2022
University of Kent
2016
London Centre for Nanotechnology
2007-2010
University College London
2001-2010
Université Joseph Fourier
2009
Centre National de la Recherche Scientifique
2009
European Synchrotron Radiation Facility
2007
Royal Institution of Great Britain
2001-2005
Magnetic Monopoles Magnets come with a north and south pole. Despite being predicted to exist, searches in astronomy high-energy particle physics experiments for magnetic monopoles (either or on their own) have defied observation. Theoretical work condensed-matter systems has that spin-ice structures may harbor such elusive particles (see the Perspective by Gingras ). Fennell et al. (p. 415 , published online 3 September) Morris 411 used polarized neutron scattering probe spin structure...
The pyrochlore material Ho2Ti2O7 has been suggested to show "spin ice" behavior. We present neutron scattering and specific heat results that establish unambiguously exhibits spin ice correlations at low temperature. Diffuse magnetic is quite well described by a nearest neighbor model very accurately dipolar model. capacity accounted for the sum of contribution an expected nuclear contribution, known exist in other Ho3+ salts. These settle question nature temperature which contradictory...
Er_2Ti_2O_7 has been suggested to be a realization of the frustrated < 111 > XY pyrochlore lattice antiferromagnet, for which theory predicts fluctuation-induced symmetry breaking in highly degenerate ground state manifold. We present theoretical analysis classical model compared neutron scattering experiments on real material, both below and above T_N = 1.173(2) K. The correctly ordered magnetic structure, suggesting that system order stabilised by zero-point quantum fluctuations can...
We report the low-temperature magnetic properties of Ce2Sn2O7, a rare-earth pyrochlore. Our susceptibility and magnetization measurements show that due to thermal isolation Kramers doublet ground state, Ce2Sn2O7 has Ising-like moments ∼1.18 μ_{B}. The are confined local trigonal axes, as in spin ice, but exchange interactions antiferromagnetic. Below 1 K, system enters regime with antiferromagnetic correlations. In contrast predictions for classical ⟨111⟩-Ising spins on pyrochlore lattice,...
At low temperatures, ${\mathrm{Tb}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ enters a spin liquid state, despite expectations of magnetic order and/or structural distortion. Using neutron scattering, we have discovered that in this state an excited crystal field level is coupled to transverse acoustic phonon, forming hybrid excitation. Magnetic and phononlike branches with identical dispersion relations can be identified, the hybridization vanishes paramagnetic state. We suggest aptly named...
The rare earth pyrochlore material Gd2Ti2O7 is considered to be an ideal model frustrated Heisenberg antiferromagnet with additional dipolar interactions. For this system there are several untested theoretical predictions of the ground state ordering pattern. Here we establish magnetic structure isotopically enriched (160)Gd2Ti2O7, using powder neutron diffraction at a temperature 50 mK. partially ordered, non-collinear antiferromagnetic structure, propagation vector k= 1/2 1/2. It can...
Dy2Ti2O7 is a geometrically frustrated magnetic material with strongly correlated spin ice regime that extends from 1 K down to as low 60 mK. The diffuse elastic neutron scattering intensities in the can be remarkably well described by phenomenological model of weakly interacting hexagonal clusters, invoked other magnets. We present highly refined microscopic theory includes long-range dipolar and exchange interactions third nearest neighbors which demonstrates clusters are purely fictitious...
We investigate the low-temperature state of rare-earth pyrochlore Tb(2)Ti(2)O(7) using polarized neutron scattering. is often described as an antiferromagnetic spin liquid with correlations extending over lengths comparable to individual tetrahedra lattice. confirm this picture at 20 K but find that 0.05 data contain evidence pinch-point scattering, suggesting low temperature has power-law correlations.
In this work, we present inelastic neutron scattering experiments which probe the single ion ground states of rare-earth pyrochlores ${R}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ ($R=\text{Tb}$, Dy, Ho). ${\text{Dy}}_{2}{\text{Ti}}_{2}{\text{O}}_{7}$ and ${\text{Ho}}_{2}{\text{Ti}}_{2}{\text{O}}_{7}$ are dipolar spin ices, now often described as hosts emergent magnetic monopole excitations; low-temperature state ${\text{Tb}}_{2}{\text{Ti}}_{2}{\text{O}}_{7}$ has features both liquids glasses,...
We report the low temperature magnetic properties of pyrochlore ${\mathrm{Pr}}_{2}{\mathrm{Hf}}_{2}{\mathrm{O}}_{7}$. Polycrystalline and single-crystal samples are investigated using time-of-flight neutron spectroscopy macroscopic measurements, respectively. The crystal-field splitting produces a non-Kramers doublet ground state for ${\mathrm{Pr}}^{3+}$, with Ising-like anisotropy. Below 0.5 K ferromagnetic correlations develop, which suggests that system enters spin-ice-like associated...
Abstract Magnon polarons are novel elementary excitations possessing hybrid magnonic and phononic signatures, responsible for many exotic spintronic phenomena. Despite long-term sustained experimental efforts in chasing magnon polarons, direct spectroscopic evidence of their existence is hardly observed. Here, we report the observation using neutron spectroscopy on a multiferroic Fe 2 Mo 3 O 8 strong magnon-phonon coupling. Specifically, below magnetic ordering temperature, gap opens at...
At low temperatures, a spin ice enters Coulomb phase - state with algebraic correlations and topologically constrained configurations. In Ho2Ti2O7, we have observed experimentally that this process is accompanied by non-standard temperature evolution of the wave vector dependent magnetic susceptibility, as measured neutron scattering. Analytical numerical approaches reveal signatures crossover between two Curie laws, one characterizing high paramagnetic regime, other which call liquid law....
The charge ordered structure of ions and vacancies characterizing rare-earth pyrochlore oxides serves as a model for the study geometrically frustrated magnetism. organization magnetic into networks corner-sharing tetrahedra gives rise to highly correlated phases with strong fluctuations, including spin liquids ices. It is an open question how these ground states governed by local rules are affected disorder. In Tb$_2$Hf$_2$O$_7$, we demonstrate that vicinity disordering transition towards...
Superconducting domes, ubiquitous across a variety of quantum materials, are often understood as window in which pairing is favored, opened by the fluctuations competing orders. Yet, understanding how such closes missing. Here, we show that inelastic neutron scattering, quantifying length scale associated with dipoles correlation, ℓ0, addresses this issue. We find that, within experimental precision, end superconducting dome coincides highly polarizable state (in ℓ0 longer than interatomic...
The magnetic dynamics of the spin ice material Ho2Ti2O7 in its paramagnetic ('hot') phase have been investigated by a combination neutron echo and ac-susceptibility techniques. Relaxation at high temperatures (T > 15 K) is proved to occur thermally activated single-ion process that distinct from dominates lower (1 K < T K). It argued low-temperature must involve quantum mechanical tunnelling, as quasi-classical channels relaxation are exhausted this temperature range. Our results resolve...
Neutron scattering and ac-susceptibility techniques have been performed on the spin ice material Ho2Ti2O7 to study relaxation processes in 'hot' paramagnetic phase (T>1 K). echo (NSE) proves that above K dynamics are governed by a thermally activated single-ion process. At lower temperatures (T<15 K) this cannot account for found measurements. It is inferred second, slower process, with different thermal signature dominates. We suggest quantum-mechanical tunnelling process between states...
Neutron diffraction has been used to investigate the magnetic correlations in single crystals of spin ice materials ${\mathrm{Ho}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ and ${\mathrm{Dy}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ an external field applied along either $[001]$ or $[1\overline{1}0]$ crystallographic directions. With a long range ordered ground state is selected from manifold. system separated into parallel $(\ensuremath{\alpha})$ perpendicular $(\ensuremath{\beta})$ chains with...
Sr_{2}CuTeO_{6} presents an opportunity for exploring low-dimensional magnetism on a square lattice of S=1/2 Cu^{2+} ions. We employ ab initio multireference configuration interaction calculations to unravel the electronic structure and evaluate exchange interactions in Sr_{2}CuTeO_{6}. The latter results are validated by inelastic neutron scattering using linear spin-wave theory series-expansion corrections quantum effects extract true coupling parameters. Using this methodology, which is...
Abstract In vortex-like spin arrangements, multiple spins can combine into emergent multipole moments. Such moments have broken space-inversion and time-reversal symmetries, therefore exhibit linear magnetoelectric (ME) activity. Three types of such are known: toroidal; monopole; quadrupole So far, however, the ME activity these has only been established experimentally for toroidal moment. Here we propose a magnetic square cupola cluster, in which four corner-sharing square-coordinated...