34 research outputs found
Confirming the high pressure phase diagram of the Shastry-Sutherland model
A Muon Spin Rotation (+SR) study was conducted to investigate the
magnetic properties of SrCu2(BO3)2 (SCBO) as a function of
temperature/pressure. Measurements in zero field and transverse field confirm
the absence of long range magnetic order at high pressures and low
temperatures. These measurements suggest changes in the Cu spin fluctuations
characteristics above 21 kbar, consistent with the formation of a plaquette
phase as previously suggested by inelastic neutron scattering measurements.
SCBO is the only known realisation of the Shatry-Sutherland model, thus the
ground state mediating the dimer and antiferromagnetic phase is likekly to be a
plaquette state
Magnetic nature of wolframite MgReO
Rhenium oxides belonging to the family ReO where is a metal
cation, exhibit interesting electronic and magnetic properties. In this study
we have utilized the muon spin rotation/relaxation (SR) technique to
study the magnetic properties of the MgReO compound. To the best of our
knowledge, this is the first investigation reported on this interesting
material, that is stabilized in a wolframite crystal structure using a special
high-pressure synthesis technique. Bulk magnetic studies show the onset of an
antiferromagnetic (AF) long range order, or a possible singlet spin state at
~K, with a subtle second high-temperature transition at
~K. Both transitions are also confirmed by heat capacity
() measurements. From our SR measurements, it is clear that the
sample enters an AF order below ~K. We find no
evidence of magnetic signal above , which indicates that is likely linked to a structural transition. Further, via sensitive zero
field (ZF) SR measurements we find evidence of a spin reorientation at
~K. This points towards a transition from a collinear AF
into a canted AF order at low temperature, which is proposed to be driven by
competing magnetic interactions
Magnetic phase boundary of BaVS3 clarified with high-pressure mu+SR
The magnetic nature of the quasi-one-dimensional BaVS3 has been studied as a function of temperature down to 0.25 K and pressure up to 1.97 GPa on a powder sample using the positive muon spin rotation and relaxation (mu(+) SR) technique. At ambient pressure, BaVS3 enters an incommensurate antiferromagnetic ordered state below the Neel temperature (T-N)31 K. T-N is almost constant as the pressure (p) increases from ambient pressure to 1.4 GPa, then T-N decreases rapidly for p > 1.4 GPa, and finally disappears at p similar to 1.8 GPa, above which a metallic phase is stabilized. Hence, T-N is found to be equivalent to the pressure-induced metal-insulator transition temperature (T-MI) at p > 1.4 GPa
Na-ion mobility in P2-type Na0.5MgxNi0.17-xMn0.83O2 (0
Sodium transition metal oxides with a layered structure are one of the most widely studied cathode materials for Na+-ion batteries. Since the mobility of Na+ in such cathode materials is a key factor that governs the performance of material, electrochemical and muon spin rotation and relaxation techniques are here used to reveal the Na+-ion mobility in a P2-type Na0.5MgxNi0.17-xMn0.83O2 (x = 0, 0.02, 0.05 and 0.07) cathode material. Combining electrochemical techniques such as galvanostatic cycling, cyclic voltammetry, and the galvanostatic intermittent titration technique with mu+SR, we have successfully extracted both self-diffusion and chemical-diffusion under a potential gradient, which are essential to understand the electrode material from an atomic-scale viewpoint. The results indicate that a small amount of Mg substitution has strong effects on the cycling performance and the Na+ mobility. Amongst the tested cathode systems, it was found that the composition with a Mg content of x = 0.02 resulted in the best cycling stability and highest Na+ mobility based on electrochemical and mu+SR results. The current study clearly shows that for developing a new generation of sustainable energy-storage devices, it is crucial to study and understand both the structure as well as dynamics of ions in the material on an atomic level
Revised Magnetic Structure and Tricritical Behavior of the CMR Compound NaCrO Investigated with High Resolution Neutron Diffraction and SR
The mixed valence Cr compound NaCrO, synthesized using a
high-pressure technique, offers a unique playground for investigating
unconventional physical properties in condensed matter. In the present study,
muon spin rotation/relaxation (SR) and high-resolution neutron powder
diffraction (NPD) measurements were carried out to clarify the true magnetic
ground state of this interesting compound. Our detailed study brings new
insight, allowing us to confirm the existence of a commensurate
antiferromagnetic order (C-AFM) and to extract its ordered Cr moment . Such a value of the ordered moment is in fact
compatible with the existence of high-spin Cr sites. Further, the value of the
canting angle of the Cr spin axial vector is refined as . Employing high-quality samples in combination with
time-of-flight NPD, a novel magnetic supercell was also revealed. Such
supercell display an incommensurate (IC)-AFM propagation vector
(0~0~), having an ordered moment . It is suggested that the C-AFM and IC-AFM
modulations are due to itinerant and localized contributions to the magnetic
moment, respectively. Finally, the direct measurement of the magnetic order
parameter provided a value of the critical exponent , suggesting a non conventional critical behavior for the magnetic
phase transition in NaCrO
Structural Evolution and Onset of the Density Wave Transition in the CDW Superconductor LaPtSi Clarified with Synchrotron XRD
The quasi-2D Pt-based rare earth intermetallic material LaPtSi has
attracted attention as it exhibits strong interplay between charge density wave
(CDW) and and superconductivity (SC). However, the most of the results reported
on this material come from theoretical calculations, preliminary bulk
investigations and powder samples, which makes it difficult to uniquely
determine the temperature evolution of its crystal structure and, consequently,
of its CDW transition. Therefore, the published literature around
LaPtSi is often controversial. In this paper, we clarify the complex
evolution of the crystal structure, and the temperature dependence of the
development of density wave transitions, in good quality LaPtSi single
crystals, with high resolution synchrotron X-ray diffraction data. According to
our findings, on cooling from room temperature LaPtSi undergoes a
series of subtle structural transitions which can be summarised as follows:
second order commensurate tetragonal ()-to-incommensurate structure
followed by a first order incommensurate-to-commensurate orthorhombic ()
transition and then a first order commensurate orthorhombic
()-to-commensurate tetragonal (). The structural transitions are
accompanied by both incommensurate and commensurate superstructural distortions
of the lattice. The observed behavior is compatible with discommensuration of
the CDW in this material
Magnetic Properties of Multifunctional LiFePO under Hydrostatic Pressure
LiFePO (LFPO) is an archetypical and well-known cathode material for
rechargeable Li-ion batteries. However, its quasi-one-dimensional (Q1D)
structure along with the Fe ions, LFPO also displays interesting
low-temperature magnetic properties. Our team has previously utilized the muon
spin rotation (SR) technique to investigate both magnetic spin order as
well as Li-ion diffusion in LFPO. In this initial study we extend our
investigation and make use of high-pressure SR to investigate effects on
the low- magnetic order. Contrary to theoretical predictions we find that
the magnetic ordering temperature as well as the ordered magnetic moment
increase at high pressure (compressive strain).Comment: 8 pages, 6 figures, submitted as a part of the International
Conference on Muon Spin Rotation, Relaxation and Resonance 2022. Accepted Dec
202
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Engineering a pure Dirac regime in ZrTe5
Real-world topological semimetals typically exhibit Dirac and Weyl nodes that coexist with trivial Fermi pockets. This tends to mask the physics of the relativistic quasiparticles. Using the example of ZrTe5, we show that strain provides a powerful tool for in-situ tuning of the band structure such that all trivial pockets are pushed far away from the Fermi energy, but only for a certain range of Van der Waals gaps. Our results naturally reconcile contradicting reports on the presence or absence of additional pockets in ZrTe5, and provide a clear map of where to find a pure three-dimensional Dirac semimetallic phase in the structural parameter space of the material
Engineering a pure Dirac regime in ZrTe
Real-world topological semimetals typically exhibit Dirac and Weyl nodes that
coexist with trivial Fermi pockets. This tends to mask the physics of the
relativistic quasiparticles. Using the example of ZrTe, we show that strain
provides a powerful tool for in-situ tuning of the band structure such that all
trivial pockets are pushed far away from the Fermi energy, but only for a
certain range of Van der Waals gaps. Our results naturally reconcile
contradicting reports on the presence or absence of additional pockets in
ZrTe, and provide a clear map of where to find a pure three-dimensional
Dirac semimetallic phase in the structural parameter space of the material.Comment: 17 page