32 research outputs found
Microscopic Evidence of Spin State Order and Spin State Phase Separation in Layered Cobaltites RBaCo2O5.5 with R=Y, Tb, Dy, and Ho
We report muon spin relaxation measurements on the magnetic structures of
RBaCo_2O_5.5 with R=Y, Tb, Dy, and Ho. Three different phases, one
ferrimagnetic and two antiferromagnetic, are identified below 300 K. They
consist of different ordered spin state arrangements of high-, intermediate-,
and low-spin Co^3+ of CoO_6 octahedra. Phase separation into well separated
regions with different spin state order is observed in the antiferromagnetic
phases. The unusual strongly anisotropic magnetoresistance and its onset at the
FM-AFM phase boundary is explained.Comment: 4 pages, accepted for publication in Phys. Rev. Let
Anomalous optical phonons in FeTe pnictides: spin state, magnetic order, and lattice anharmonicity
Polarized Raman-scattering spectra of non-superconducting, single-crystalline
FeTe are investigated as function of temperature. We have found a relation
between the magnitude of ordered magnetic moments and the linewidth of A1g
phonons at low temperatures. This relation is attributed to the intermediate
spin state (S=1) and the orbital degeneracy of the Fe ions. Spin-phonon
coupling constants have been estimated based on microscopic modeling using
density-functional theory and analysis of the local spin density. Our
observations show the importance of orbital degrees of freedom for the Fe-based
superconductors with large ordered magnetic moments, while small magnetic
moment of Fe ions in some iron pnictides reflects the low spin state of Fe ions
in those systems.Comment: 17 pages, 3 figure
Phase separation in iron chalcogenide superconductor Rb0.8+xFe1.6+ySe2 as seen by Raman light scattering and band structure calculations
We report Raman light scattering in the phase separated superconducting
single crystal Rb0.77Fe1.61Se2 with Tc = 32 K. The spectra have been measured
in a wide temperature range 3K -500K. The observed phonon lines from the
majority vacancy ordered Rb2Fe4Se5 (245) antiferromagnetic phase with TN= 525 K
demonstrate modest anomalies in frequency, intensity and halfwidth at the
superconductive phase transition. We identify phonon lines from the minority
compressed Rb{\delta}Fe2Se2 (122) conductive phase. The superconducting gap
with dx2-y2 symmetry is also detected in our spectra. In the range 0-600 cm-1
we observed the low intensive but highly polarized B1g-type background which
becomes well structured under cooling. The possible magnetic or multiorbital
origin of this background has been discussed. We argue that phase separation in
M0.8+xFe1.6+ySe2 has pure magnetic origin. It occurs below Neel temperature
when iron magnetic moment achieves some critical magnitude. We state that there
is a spacer between the majority 245 and minority 122 phases. Using ab-initio
spin polarized band structure calculations we demonstrate that compressed
vacancy ordered Rb2Fe4Se5 phase can be conductive and therefore may serve as a
protective interface spacer between the pure metallic Rb{\delta}Fe2Se2 phase
and the insulating Rb2Fe4Se5 phase providing the percolative Josephson-junction
like superconductivity in the whole sample of Rb0.8+xFe1.6+ySe2 Our lattice
dynamics calculations show significant difference in the phonon spectra of the
conductive and insulating Rb2Fe4.Se5 phases.Comment: This paper is devoted to the memory of academician Kirill Borisovich
Tolpygo, prominent Physicist, Teacher and Citizen, who made a great
contribution to the lattice dynamics theory and many other branches of solid
state physic
Low-dimensional magnetism of spin-½ chain systems α- and β-TeVO₄: a comparative study
We present a comparative study of the low-dimensional compounds α- and β-TeVO₄. Our data clearly show
that the change in the local coordination geometry of V⁴⁺ ions comparing α- and β-TeVO₄ leads to a drastic differences
in the magnetic properties. Despite sharing the same crystal structure, the two compounds realize different
magnetic exchange topologies. Both compounds exhibit a transition from ferro- to antiferromagnetic correlations
with decreasing temperature. This effect however is driven by different mechanisms for both compounds.
Additionally, a dimensional crossover is found in β-TeVO₄
Phase separation in iron chalcogenide superconductor Rb₀.₈₊xFe₁.₆₊ySe₂ as seen by Raman light scattering and band structure calculations
We report Raman light scattering in the phase separated superconducting single crystal Rb₀.₇₇Fe₁.₆₁Se₂ with Tc = 32 K over a wide temperature region 3–500 K. The observed phonon lines from the majority vacancy ordered Rb₂Fe₄Se₅ (245) antiferromagnetic phase with TN = 525 K demonstrate modest anomalies in the frequency, intensity and halfwidth at the superconductive phase transition. We identify phonon lines from the minority compressed RbδFe₂Se₂ (122) conductive phase. The superconducting gap with dx₂₋y₂ symmetry has been detected in our spectra. In the range 0–600 cm–¹ we observe a weak but highly polarized B₁g-type backgroundwhich becomes well-structured upon cooling. A possible magnetic or multiorbital origin of this background is discussed. We argue that the phase separation in M₀.₈₊xFe₁.₆₊ySe₂ is of pure magnetic origin. It occurs below the Néel temperature when the magnetic moment of iron reaches a critical value. We state that there is a spacer between the majority 245 and minority 122 phases. Using ab initio spin-polarized band structure calculations we demonstrate that the compressed vacancy ordered Rb₂Fe₄Se₅ phase can be conductive and therefore may serve as a protective interface spacer between the purely metallic RbδFe₂Se₂ phase and the insulating Rb₂Fe₄Se₅ phase providing percolative Josephson-junction like superconductivity all throughout of Rb₀.₈₊xFe₁.₆₊ySe₂. Our lattice dynamics calculations show significant differences in the phonon spectra of the conductive and insulating Rb₂Fe₄Se₅ phases
Magnetoelectricity in the ferrimagnetic Cu2OSeO3: symmetry analysis and Raman scattering study
sublattices ferrimagnet Cu2OSeO3 with a cubic symmetry and a linear
magnetoelectric effect. There is no spectroscopic evidence for
structural lattice distortions below T-C=60 K, which are expected due to
magnetoelectric coupling. Using symmetry arguments we explain this
observation by considering a special type of ferrimagnetic ground state
which does not generate a spontaneous electric polarization.
Interestingly, Raman scattering shows a strong increase of electric
polarization of media through a dynamic magnetoelectric effect as a
remarkable enhancement of the scattering intensity below T-C. New lines
of purely magnetic origin have been detected in the magnetically ordered
state. A part of them are attributed as scattering on exchange magnons.
Using this observation and further symmetry considerations we argue for
strong Dzyaloshinskii-Moriya interaction existing in the Cu2OSeO3. (c)
2010 American Institute of Physics. [doi:10.1063/1.3455808]]]>
eng
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https://serval.unil.ch/notice/serval:BIB_C998E6489D93
Innovations pragmatiques, recherche d'évidences et évaluations, dans la construction et la poursuite d'une politique publique de la drogue.
Dubois-Arber, Françoise
Lehmann, Philippe
info:eu-repo/semantics/bookPart
incollection
2012
Drogenpolitik als Gesellschaftspolitik: ein Rückblick auf dreissig Jahre Schweizer Drogenpolitik, 1981-2011 = La politique drogue en tant que politique de société: un rétrospectif sur trente ans de politique suisse en matière de drogues, 1981-2011, pp. 50-58
info:eu-repo/semantics/altIdentifier/isbn/978-3-03777-114-3
info:eu-repo/semantics/altIdentifier/isbn/978-2-88351-057-9
Substance-Related Disorders ; Public Policy ; Program Evaluation ; Switzerland
fre
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Olanzapine or chlorpromazine plus lithium in first episode psychotic mania: An 8-week randomised controlled trial.
info:doi:10.1016/j.eurpsy.2015.09.009
info:eu-repo/semantics/altIdentifier/doi/10.1016/j.eurpsy.2015.09.009
info:eu-repo/semantics/altIdentifier/pmid/26485297
Conus, P.
Berk, M.
Cotton, S.M.
Kader, L.
Macneil, C.
Hasty, M.K.
Hallam, K.
Lambert, M.
Murphy, B.P.
McGorry, P.D.
info:eu-repo/semantics/article
article
2015
European Psychiatry, vol. 30, no. 8, pp. 975-982
info:eu-repo/semantics/altIdentifier/eissn/1778-3585
urn:issn:0924-9338
<![CDATA[BACKGROUND: Treatment strategies for mental disorders may vary according to illness stage. However no data currently exist to guide treatment in first episode psychotic mania. The aim of this study was to compare the safety and efficacy profile of chlorpromazine and olanzapine, as add-on to lithium, in patients with a first episode of psychotic mania, expecting better safety profile and adherence to olanzapine but similar efficacy for both treatments.
METHODS: Data from 83 patients were collected in an 8-week randomised controlled trial on clinical variables, side effects, vital signs, and weight. Analyses of treatment differences over time were based on intent-to-treat principles. Kaplan-Meier estimated survival curves were used to analyse time-to-event data and mixed effects models repeated measures analysis of variance were used to determine treatment group differences over time on safety and efficacy measures.
RESULTS: Ethics committee approval to delay informed consent procedure until recovery from the acute episode allowed the inclusion of 83 patients highly representative of those treated in the public sector. Contrary to our hypotheses, safety profile of both medications was similar. A signal for higher rate (P=.032) and earlier occurrence (P=.043) of mania remission was observed in the olanzapine group which did not survive correction for multiple comparisons.
CONCLUSIONS: Olanzapine and chlorpromazine have a similar safety profile in a uniquely representative cohort of patients with first episode psychotic mania. The possibility for a greater impact of olanzapine on manic symptoms leading to earlier remission of the episode needs exploration in a large sample