19 research outputs found
Understanding the magnetism in noncentrosymmetric CeIrGe3 Muon spin relaxation and neutron scattering studies
The magnetic properties of a pressure induced noncentrosymmetric
heavy-fermion superconductor CeIrGe have been investigated by muon spin
relaxation (SR), powder neutron diffraction (ND) and inelastic neutron
scattering (INS) techniques at ambient pressure. For completeness we have also
measured the ac magnetic susceptibility , dc magnetic
susceptibility , dc isothermal magnetization and heat capacity
down to 2 K. CeIrGe is known to exhibit pressure induced
superconductivity ( K) at a pressure of 20 GPa and
antiferromagnetic ordering at 8.7 K, 4.7 K and 0.7 K at ambient pressure. Our
and data show an additional anomaly near 6.2 K
which is also captured in data. From ,
and measurements we infer three antiferromagnetic
transitions above 2 K at K, K and K. Our SR study also confirms the presence of three transitions
through the observation of one frequency for ,
two frequencies for and three frequencies for
in the oscillatory asymmetry. The ND data reveal an
incommensurate nature of the magnetic ordering at K with the propagation
vector k = (0,0,0.688(3)), and a commensurate magnetic structure at K
with the propagation vector locked to the value k = (0,0,2/3) and magnetic
moments oriented along the axis. The commensurate structure couples a
macroscopic ferromagnetic component, resulting in a strong dependence of the
lock-in transition temperature on external magnetic field. The INS data show
two well defined crystal electric field (CEF) excitations arising from the
CEF-split Kramers doublet ground state of Ce.Comment: 13 pages, 16 figures, 1 tabl
Investigating the magnetic ground state of the skyrmion host material Cu2OSeO3 using long-wavelength neutron diffraction
We present long-wavelength neutron diffraction data measured on both single crystal and polycrystalline samples of the skyrmion host material Cu2OSeO3. We observe magnetic satellites around the (01⎯⎯1) diffraction peak not accessible to other techniques, and distinguish helical from conical spin textures in reciprocal space. Our measurements show that not only the field-polarised phase but also the helical ground state are made up of ferrimagnetic clusters instead of individual spins. These clusters are distorted Cu tetrahedra, where the spin on one Cu ion is anti-aligned with the spin on the three other Cu ions
Composition-, temperature- and pressure-induced transitions between high-pressure stabilized perovskite phases of the (1-x)BiFe0.5Sc0.5O3 - xLaFe0.5Sc0.5O3 series
Crystal structures of the high-pressure synthesized perovskite phases of the (1-x)BiFe0.5Sc0.5O3-xLaFe0.5Sc0.5O3 (0 ​= ​x ​≤ ​1) system and their temperature and pressure behaviours were studied using laboratory and synchrotron X-ray diffractions as well as neutron diffraction. At room temperature, the as-prepared phases with x ​≤ ​0.05 have an antipolar structure with the Pnma symmetry and with the √2ap ​× ​4ap ​× ​2√2ap superstructure (where ap is the pseudocubic perovskite unit-cell parameter). An incommensurately modulated phase with the Imma(00γ)s00 superspace group is observed for 0.10 ​= ​x ​≤ ​0.33, while a non-polar Pnma phase (√2ap ​× ​2ap ​× ​√2ap) is stable when x ​≥ ​0.34. The antipolar Pnma phase in the as-prepared samples with composition corresponding to x ​= ​0 transforms into the polar Ima2 one via irreversible annealing-caused transformation accompanied by a formation of a high-temperature intermediate polar R3c polymorph, while the antipolar Pnma phase in samples with x ​= ​0.05 is stable until the decomposition temperature. In the solid solutions with 0.10 ​= ​x ​≤ ​0.33, increasing temperature was found to result in a reversible transformation of the Imma(00γ)s00 phase into a non-polar Pnma one. The transition temperature decreases with increasing x. A hydrostatic pressure of few GPa was also shown to induce a reversible Imma(00γ)s00 → Pnma transformation.publishe
Synchronization of multi-phase oscillators: An Axelrod-inspired model
Inspired by Axelrod's model of culture dissemination, we introduce and
analyze a model for a population of coupled oscillators where different levels
of synchronization can be assimilated to different degrees of cultural
organization. The state of each oscillator is represented by a set of phases,
and the interaction --which occurs between homologous phases-- is weighted by a
decreasing function of the distance between individual states. Both ordered
arrays and random networks are considered. We find that the transition between
synchronization and incoherent behaviour is mediated by a clustering regime
with rich organizational structure, where some of the phases of a given
oscillator can be synchronized to a certain cluster, while its other phases are
synchronized to different clusters.Comment: 6 pages, 5 figure
Singularities of Magnetic and Elastic Characteristics of La2/3Ba1/3MnO3: Analysis of Martensitic Kinetics
A coordinated temperature behavior of magnetic susceptibility and internal
friction has been observed in the La2/3Ba1/3MnO3 manganite in the temperature
region of the crystal phase separation 5-340 K. Stepwise temperature behavior
of the susceptibility of the single crystal sample and corresponding singular
behavior of the internal friction in the polycrystalline manganite have been
found. These small-scale features of the temperature dependences of the
susceptibility and the internal friction are considered to be a reflection of
martensitic kinetics of the structural phase transformation R3c-Imma in the 200
K temperature region.Comment: 13 pages, 4 figures, Submitted J. Magn. Magn. Mate
Magnetic properties of the Bi0.65La0.35Fe0.5Sc0.5O3 perovskite
Magnetic properties of polycrystalline multiferroic Bi0.65La0.35Fe0.5Sc0.5O3 synthesized under high-pressure (6 GPa) and high-temperature (1500 K) conditions were studied using a SQUID magnetometer technique. The temperature dependent static magnetic moment M was measured in both zero-field-cooled and field-cooled modes over the temperature range of 5-300 K in low magnetic field H = 0.02 kOe. The field dependent magnetization M(H) was measured in magnetic fields up to 50 kOe at different temperatures up to 230 K after zero-field cooling procedure. A long-range magnetic ordering of the antiferromagnetic type with a weak ferromagnetic contribution takes place below TN ≈ 220 K. Magnetic hysteresis loops taken below TN show a huge coercive field up to Hc ≈ 10 kOe, while the magnetic moment does not saturate up to 50 kOe. A strong effect of magnetic field on the magnetic properties of the compound has been found. Below TN ≈ 220 K the derivatives of the initial magnetization curves demonstrate the existence of a temperature-dependent anomaly in fields of H = 15÷25 kOe. The nature of the anomaly is unknown and requires additional study.publishe
Spin state ordering and magnetic structures in the cobaltites YBaCo2O5 delta delta 0.50 and 0.44
The antiferromagnetic ferromagnetic phase transition in YBaCo2O5.50 and YBaCo2O5.44 cobaltites with different types of oxygen ion ordering in the [YO0.5 0.44] layers has been studied by neutron powder diffraction in combination with group theoretical analysis. As a result, the crystal and magnetic structures above and below the phase transformation temperature Ti were determined and successfully refined. In both cases, the proposed models involve a spin state ordering between diamagnetic t lt;sub gt;2g lt; sub gt; lt;sup gt;6 lt; sup gt;e lt;sub gt;g lt; sub gt; lt;sup gt;0 lt; sup gt;, S 0 and paramagnetic t lt;sub gt;2g lt; sub gt; lt;sup gt;4 lt; sup gt;e lt;sub gt;g lt; sub gt; lt;sup gt;2 lt; sup gt;, S 2 Co3 ions with octahedral coordination. Electronic ordering results in a nonzero spontaneous magnetic moment in the high temperature magnetic phases with isotropic negative exchange interactions. In the case of YBaCo2O5.5, the phase transformation does not change the Pmma 2ap 2ap 2ap symmetry of the crystal structure. The wave vectors of magnetic structures above and below Ti are k 0 and k c 2, respectively. In the case of YBaCo2O5.44 a crossover P4 nmm 3sqrt 2 ap 3sqrt 2 ap 2ap gt;I4 mmm 3sqrt 2 ap 3sqrt 2 ap 4ap was involved to solve the low temperature magnetic structure. The wave vectors in both high temperature and low temperature magnetic phases are k 0. Mechanisms of the phase transformation in both compositions are discussed in the light of obtained magnetic structures. The proposed spin configurations were compared with other models reported in literatur
Modulated spin helicity stabilized by incommensurate orbital density waves in a quadruple perovskite manganite
International audienceThrough a combination of neutron diffraction and Landau theory we describe the spin ordering in the ground state of the quadruple perovskite manganite CaMn7O12 - a magnetic multiferroic supporting an incommensurate orbital density wave that onsets above the magnetic ordering temperature, TN1=90 K. The multi-k magnetic structure in the ground state was found to be a nearly-constant-moment helix with modulated spin helicity, which oscillates in phase with the orbital occupancies on the Mn3+ sites via trilinear magneto-orbital coupling. Our phenomenological model also shows that, above TN2=48 K, the primary magnetic order parameter is locked into the orbital wave by an admixture of helical and collinear spin density wave structures. Furthermore, our model naturally explains the lack of a sharp dielectric anomaly at TN1 and the unusual temperature dependence of the electrical polarization. © 2016 American Physical Society