47 research outputs found
Magnetic order and transitions in the spin-web compound Cu3TeO6
The spin-web compound Cu3TeO6, belongs to an intriguing group of materials
where magnetism is governed by 3d9 copper Cu2+ ions. This compound has been
sparsely experimentally studied and we here present the first investigation of
its local magnetic properties using muon-spin relaxation/rotation ({\mu}+SR).
Our results show a clear long-range 3D magnetic order below TN as indicated by
clear zero-field (ZF) muon-precessions. At TN = 61.7 K a very sharp transition
is observed in the weak transverse-field (wTF) as well as ZF data. Contrary to
suggestions by susceptibility measurements and inelastic neutron scattering, we
find no evidence for either static or dynamic (on the time-scale of {\mu}+SR)
spin-correlations above TN
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
Confirming the high pressure phase diagram of the Shastry-Sutherland model
A Muon Spin Rotation (μ + 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 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
Pressure dependence of ferromagnetic phase boundary in BaVSe3 studied with high-pressure μ+SR
The magnetic nature of a quasi-one-dimensional compound, BaVSe3, has been investigated with positive muon spin rotation and relaxation (μ+SR) measurements at ambient and high pressures. At ambient pressure, the μ+SR spectrum recorded under zero external magnetic field exhibited a clear oscillation below the Curie temperature (TC∼41K) due to the formation of quasistatic ferromagnetic order. The oscillation consisted of two different muon spin precession signals, indicating the presence of two magnetically different muon sites in the lattice. However, the two precession frequencies, which correspond to the internal magnetic fields at the two muon sites, could not be adequately explained with relatively simple ferromagnetic structures using the muon sites predicted by density functional theory calculations. The detailed analysis of the internal magnetic field suggested that the V moments align ferromagnetically along the c axis but slightly canted toward the a axis by 28 that is coupled antiferromagnetically. The ordered V moment (MV) is estimated as (0.59, 0, 1.11) μB. As pressure increased from ambient pressure, TC was found to decrease slightly up to about 1.5 GPa, at which point TC started to increase rapidly with the further increase of the pressure. Based on a strong ferromagnetic interaction along the c axis, the high-pressure μ+SR result revealed that there are two magnetic interactions in the ab plane; one is an antiferromagnetic interaction that is enhanced with pressure, mainly at pressures below 1.5 GPa, while the other is a ferromagnetic interaction that becomes predominant at pressures above 1.5 GPa
Pressure driven magnetic order in Sr 1-x Ca x Co 2 P 2
The magnetic phase diagram of Sr1-xCaxCo2P2 as a function of hydrostatic pressure and temperature is investigated by means of high pressure muon spin rotation, relaxation and resonance (μ+SR). The weak pressure dependence for the x≠1 compounds suggests that the rich phase diagram of Sr1-xCaxCo2P2 as a function of x at ambient pressure may not solely be attributed to chemical pressure effects. The x= 1 compound on the other hand reveals a high pressure dependence, where the long range magnetic order is fully suppressed at pc 2≈ 9.8 kbar, which seem to be a first order transition. In addition, an intermediate phase consisting of magnetic domains is formed above pc 1≈ 8 kbar where they co-exist with a magnetically disordered state. These domains are likely to be ferromagnetic islands (FMI) and consist of an high- (FMI-1) and low-temperature (FMI-2) region, respectively, separated by a phase boundary at Ti≈ 20 K. This kind of co-existence is unusual and is originating from a coupling between lattice and magnetic degrees of freedoms
Cation Distributions and Magnetic Properties of Ferrispinel MgFeMnO4
The crystal structure and magnetic properties of the cubic spinel MgFeMnO4 were studied by using a series of in-house techniques along with large-scale neutron diffraction and muon spin rotation spectroscopy in the temperature range between 1.5 and 500 K. The detailed crystal structure is successfully refined by using a cubic spinel structure described by the space group Fd3\uaf m. Cations within tetrahedral A and octahedral B sites of the spinel were found to be in a disordered state. The extracted fractional site occupancies confirm the presence of antisite defects, which are of importance for the electrochemical performance of MgFeMnO4 and related battery materials. Neutron diffraction and muon spin spectroscopy reveal a ferrimagnetic order below TC = 394.2 K, having a collinear spin arrangement with antiparallel spins at the A and B sites, respectively. Our findings provide new and improved understanding of the fundamental properties of the ferrispinel materials and of their potential applications within future spintronics and battery devices
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
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