391 research outputs found
Experimental Proof of a Magnetic Coulomb Phase
Spin ice materials are magnetic substances in which the spin directions map
onto hydrogen positions in water ice. Recently this analogy has been elevated
to an electromagnetic equivalence, indicating that the spin ice state is a
Coulomb phase, with magnetic monopole excitations analogous to ice's mobile
ionic defects. No Coulomb phase has yet been proved in a real magnetic
material, as the key experimental signature is difficult to resolve in most
systems. Here we measure the scattering of polarised neutrons from the
prototypical spin ice Ho2Ti2O7. This enables us to separate different
contributions to the magnetic correlations to clearly demonstrate the existence
of an almost perfect Coulomb phase in this material. The temperature dependence
of the scattering is consistent with the existence of deconfined magnetic
monopoles connected by Dirac strings of divergent length.Comment: 18 pages, 4 fig
The magnetic dynamics of NiPS
Neutron spectroscopy measurements have been performed on single crystals of
the antiferromagnetic van der Waals compound NiPS. Linear spin wave theory
using a Heisenberg Hamiltonian with single-ion anisotropies has been applied to
determine the magnetic exchange parameters and the nature of the anisotropy.
The analysis reveals that NiPS is less two-dimensional than its sister
compounds, with a relatively large ferromagnetic exchange of meV between the layered \emph{ab} planes. In-plane magnetic exchange
interactions up to the third nearest-neighbour were required to fit the data.
The nearest-neighbour exchange was ferromagnetic with meV, the
second neighbour was antiferromagnetic and small with meV, and the
dominant antiferromagnetic third neighbour exchange was meV. The
anisotropy was shown to be largely XY-like with a small uniaxial component,
leading to the appearance of two low-energy spin wave modes in the spin wave
spectrum at the Brillouin zone centre. The analysis could reproduce the spin
wave energies, however there are discrepancies with the calculated neutron
intensities hinting at more exotic phenomena.Comment: 12 pages, 8 figures, 33 reference
Dipolar spin-waves and tunable band gap at the Dirac points in the 2D magnet ErBr3
Topological magnon insulators constitute a growing field of research for
their potential use as information carriers without heat dissipation. We report
an experimental and theoretical study of the magnetic ground-state and
excitations in the van der Waals two-dimensional honeycomb magnet ErBr3. We
show that the magnetic properties of this compound are entirely governed by the
dipolar interactions which generate a continuously degenerate non-collinear
ground-state on the honeycomb lattice with spins confined in the plane. We find
that the magnon dispersion exhibits Dirac-like cones when the magnetic moments
in the ground-state are related by time-reversal and inversion symmetries
associated with a Berry phase \pi as in single-layer graphene. A magnon band
gap opens when the dipoles are rotated away from this state, entailing a finite
Berry curvature in the vicinity of the K and K' Dirac points. Our results
illustrate that the spin-wave dispersion of dipoles on the honeycomb lattice
can be reversibly controlled from a magnetic phase with Dirac cones to a
topological antiferromagnetic insulator with non-trivial valley Chern number
Reliability and accuracy of delirium assessments among investigators at multiple international centres
The elevated Curie temperature and half-metallicity in the ferromagnetic semiconductor LaEuO
Here we study the effect of La doping in EuO thin films using SQUID
magnetometry, muon spin rotation (SR), polarized neutron reflectivity
(PNR), and density functional theory (DFT). The SR data shows that the
LaEuO is homogeneously magnetically ordered up to its
elevated . It is concluded that bound magnetic polaron behavior does
not explain the increase in and an RKKY-like interaction is
consistent with the SR data. The estimation of the magnetic moment by DFT
simulations concurs with the results obtained by PNR, showing a reduction of
the magnetic moment per LaEuO for increasing lanthanum doping.
This reduction of the magnetic moment is explained by the reduction of the
number of Eu-4 electrons present in all the magnetic interactions in EuO
films. Finally, we show that an upwards shift of the Fermi energy with La or Gd
doping gives rise to half-metallicity for doping levels as high as 3.2 %.Comment: 7 pages, 11 figure
Eating Pathology Symptoms Inventory – Clinician Rated Version (EPSI-CRV)
The files in this record contain supplemental information about the EPSI-CRV including: a copy of the EPSI-CRV, suggested training plan, training videos with an example of completed ratings, and a list of items that were removed during the final development process.The Eating Pathology Symptoms Inventory – Clinician Rated Version (EPSI-CRV) is a semi-structured interview that was designed to assess dimensional constructs of eating-disorder psychopathology and generate current Diagnostic and Statistical Manual- Fifth Edition (DSM-5) eating-disorder diagnoses. The EPSI-CRV is based on the self-report version of the EPSI (Forbush et al., 2013). There are 13 modules (or sections) within the EPSI-CRV. Eight modules measure content that is assessed in the self-report version of the EPSI, including: Body Dissatisfaction, Binge Eating, Cognitive Restraint, Excessive Exercise, Restricting, Purging, Muscle Building, and Negative Attitudes Towards Obesity. Five additional modules are included to derive DSM-5 diagnoses. The five DSM-5 modules include: Subjective Binge Episodes, Binge Eating Disorder, Low Weight, Overvaluation of Weight and Shape, and Fear of Weight Gain. The average administration time is approximately 38 minutes. The EPSI-CRV is designed to be used by clinicians and researchers working with adults with eating disorders across a range of settings. The interview may be useful for making admissions decisions, treatment planning, and discharge planning, as well as for research studies
Energy separation of single-particle and continuum states in a S=1/2 weakly-coupled chains antiferromagnet
Inelastic neutron scattering is used to study transverse-polarized magnetic
excitations in the quasi-one-dimensional S=1/2 antiferromagnet BaCu_2Si_2O_7,
where the saturation value for the N\'eel order parameter is per spin. At low energies the spectrum is totally dominated by
resolution-limited spin wave-like excitations. An excitation continuum sets in
above a well-defined threshold frequency. Experimental results are discussed in
the context of current theories for weakly-interacting quantum half-integer
spin chains.Comment: 4 pages 4 figure
Iris classification based on sparse representations using on-line dictionary learning for large-scale de-duplication applications
De-duplication of biometrics is not scalable when the number of people to be enrolled into the biometric system runs into billions, while creating a unique identity for every person. In this paper, we propose an iris classification based on sparse representation of log-gabor wavelet features using on-line dictionary learning (ODL) for large-scale de-duplication applications. Three different iris classes based on iris fiber structures, namely, stream, flower, jewel and shaker, are used for faster retrieval of identities. Also, an iris adjudication process is illustrated by comparing the matched iris-pair images side-by-side to make the decision on the identification score using color coding. Iris classification and adjudication are included in iris de-duplication architecture to speed-up the identification process and to reduce the identification errors. The efficacy of the proposed classification approach is demonstrated on the standard iris database, UPOL
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