A5029394355- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- Rare-earth and actinide compounds
- Magnetic and transport properties of perovskites and related materials
- Iron-based superconductors research
- Magnetic Properties of Alloys
- 2D Materials and Applications
- Muon and positron interactions and applications
- Topological Materials and Phenomena
- Nuclear Physics and Applications
- Multiferroics and related materials
- High-pressure geophysics and materials
- Nuclear Materials and Properties
- Particle Detector Development and Performance
- Traumatic Brain Injury and Neurovascular Disturbances
- Traumatic Brain Injury Research
- Magnetic properties of thin films
- Nuclear physics research studies
- Heusler alloys: electronic and magnetic properties
- Cold Atom Physics and Bose-Einstein Condensates
- Inorganic Chemistry and Materials
- Atomic and Subatomic Physics Research
- Particle accelerators and beam dynamics
- Magneto-Optical Properties and Applications
- ZnO doping and properties
Rutherford Appleton Laboratory
2025
China Spallation Neutron Source
2025
ISIS Neutron and Muon Source
2025
Oak Ridge National Laboratory
2015-2024
Rutgers Sexual and Reproductive Health and Rights
2024
IIT@MIT
2024
National Renewable Energy Laboratory
2022-2023
Riverkeeper
2022
North Carolina Agricultural and Technical State University
2021
Indiana University – Purdue University Indianapolis
2017-2018
CrSiTe3 has attracted recent interest as a candidate single-layer ferromagnetic semiconductor, but relatively little is known about the bulk properties of this material. Here, we report single-crystal X-ray diffraction, magnetic properties, thermal conductivity, vibrational, and optical spectroscopies compare our findings with complementary electronic structure lattice dynamics principles calculations. The high temperature paramagnetic phase characterized by strong spin-lattice interactions...
Recent high-pressure studies found that structural/magnetic phase transitions are very pressure sensitive in ${\text{CaFe}}_{2}{\text{As}}_{2}$ and superconductivity can be achieved under modest pressure, although details of the sharpness temperature vary between liquid medium gas measurements. To better understand this issue, we performed susceptibility transport on ${\text{CaFe}}_{2}{\text{As}}_{2}$, using helium as medium. The signatures to low-temperature orthorhombic collapsed...
Intrinsic, two-dimensional ferromagnetic semiconductors are an important class of materials for overcoming the limitations dilute magnetic spintronics applications. CrSiTe$_3$ is a particularly interesting member this class, since it can likely be exfoliated down to single layers, where T$_C$ predicted increase dramatically. Establishing nature magnetism in bulk necessary precursor understanding behavior thin film samples and possible applications material. In work, we use elastic inelastic...
By muon spin-relaxation measurements on single-crystal specimens, we show that superconductivity in the $A{\text{Fe}}_{2}{\text{As}}_{2}$ $(A=\text{Ca},\text{Ba},\text{Sr})$ systems, both cases of composition and pressure tunings, coexists with a strong static magnetic order partial volume fraction. The superfluid response from remaining paramagnetic fraction $({\text{Ba}}_{0.5}{\text{K}}_{0.5}){\text{Fe}}_{2}{\text{As}}_{2}$ exhibits nearly linear variation $T$ at low temperatures,...
We employ NMR techniques to investigate the nature of Mn spins in I-II-V diluted magnetic semiconductor Li(Zn1-xMnx)P (x = 0.1, Curie temperature Tc 25 K). successfully identify 7Li signals arising from Li sites adjacent Mn2+, and probe static dynamic properties spins. From spin-lattice relaxation data, we show that spin-spin interactions extend over many unit cells.
Compounds with two-dimensional (2D) layers of magnetic ions weakly connected by van der Waals bonding offer routes to enhance quantum behavior, stimulating both fundamental and applied interest. ${\mathrm{CrPS}}_{4}$ is one such material, however, it has undergone only limited investigation. Here we present a comprehensive series neutron scattering measurements determine the structure exchange interactions. The observed excitations allow high degree constraint on model parameters not...
Zero-field (ZF) muon-spin-relaxation $(\ensuremath{\mu}\text{SR})$ measurements have revealed static commensurate magnetic order of Fe moments in NdFeAsO below ${T}_{N}\ensuremath{\sim}135\text{ }\text{K}$, with the ordered moment size nearly equal to that LaFeAsO, and confirmed similar behavior ${\text{BaFe}}_{2}{\text{As}}_{2}$. In single crystals superconducting ${\text{Ba}}_{0.55}{\text{K}}_{0.45}{\text{Fe}}_{2}{\text{As}}_{2}$, $\ensuremath{\mu}\text{SR}$ spectra indicate magnetism...
We have performed transverse field muon spin rotation measurements of single crystals $\text{Ba}{({\text{Fe}}_{0.926}{\text{Co}}_{0.074})}_{2}{\text{As}}_{2}$ with the applied magnetic along $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{c}$ direction. Fourier transforms measured spectra reveal an anisotropic line-shape characteristic Abrikosov vortex lattice. fit $\ensuremath{\mu}\text{SR}$ to a microscopic model in terms penetration depth $\ensuremath{\lambda}$ and Ginzburg-Landau parameter...
Theory predicts the low-temperature magnetic excitations in spin ices consist of deconfined charges, or monopoles. A recent transverse-field (TF) muon rotation (muSR) experiment [S T Bramwell et al, Nature 461, 956 (2009)] reports results claiming to be consistent with temperature and field dependence anticipated for monopole nucleation - so-called second Wien effect. We demonstrate via a new series muSR experiments Dy_2Ti_2O_7 that such an effect is not observable TF experiment. Rather, as...
We report low-temperature specific heat and positive muon spin relaxation/rotation ($\ensuremath{\mu}$SR) measurements on both polycrystalline single-crystal samples of the pyrochlore magnet Yb${}_{2}$Ti${}_{2}$O${}_{7}$. This material is believed to possess a Hamiltonian able support quantum ice (QSI) ground state. Yb${}_{2}$Ti${}_{2}$O${}_{7}$ displays sample variation in its capacity and, while our two exhibit extremes this variation, $\ensuremath{\mu}$SR indicate similar disordered state...
Fermi showed that electrons, as a result of their quantum nature, form gas particles where the temperature and density follow so called distribution. In metal, shown by Landau, despite strong Coulomb interaction with each other positive background ions, electrons continue to act like free mechanical but enhanced masses. This state matter, Landau-Fermi liquid, is recognized experimentally an electrical resistivity proportional square absolute plus term frequency applied field. Calculations...
We present high-resolution angle-resolved photoemission spectra of the heavy-fermion superconductor URu2Si2. Detailed measurements as a function both photon energy and temperature allow us to disentangle variety spectral features, revealing evolution low-energy electronic structure across "hidden order" transition. Above transition, our reveal existence weakly dispersive states that exhibit large scattering rate do not appear shift from above below Fermi level, previously reported. Upon...
Kitaev materials, based on bond-directional Ising interactions, offer an intriguing platform for hosting exotic magnetic ground states and excitations. Significant interactions are most commonly realized in heavy transition metal magnets with so-called ${J}_{\mathrm{eff}}$ = \textonehalf{} electronic the local geometries consisting of metal-ligand edge-sharing octahedra. Here, authors show that materials can also be via extended superexchange pathways mediated by more than one anion.
Replacing a magnetic atom by spinless in heavy-fermion compound generates quantum state often referred to as "Kondo-hole". No experimental imaging has been achieved of the atomic-scale electronic structure Kondo-hole, or their destructive impact [Lawrence JM, et al. (1996) Phys Rev B 53:12559-12562] [Bauer ED, (2011) Proc Natl Acad Sci. 108:6857-6861] on hybridization process between conduction and localized electrons which state. Here we report visualization at Kondo-holes created...
A special type of anisotropic spin exchange called the ``Kitaev interaction'' provides rare exactly-soluble models gapless quantum liquids in 2d and 3d. The main goals this work were to identify other lattice geometries that support elusive Kitaev interactions understand magnetic properties such materials. By performing inelastic neutron scattering on La${}_{2}$MgIrO${}_{6}$ La${}_{2}$ZnIrO${}_{6}$, authors find these magnets, which possess long-range antiferromagnetic order, yield clear...
Neutron scattering, magnetometry, and muon spin rotation ($\mu$SR) measurements were performed to investigate the magnetic order dynamics across ferromagnet-to-paramagnet transition in hole-doped Mott insulator Y$_{1-x}$Ca$_x$TiO$_3$. We find that proceeds through a volume-wise phase separation into ferromagnetic paramagnetic regions. Spin fluctuations with characteristic timescale of $\sim$ 0.1 $\mu$s, as detected via $\mu$SR, are observed appear at Ca concentrations $x \geq 0.10$. The...
We report muon spin rotation $(\ensuremath{\mu}\text{SR})$ measurements of single-crystal $\text{Ba}{({\text{Fe}}_{1\ensuremath{-}x}{\text{Co}}_{x})}_{2}{\text{As}}_{2}$ and $\text{Sr}{({\text{Fe}}_{1\ensuremath{-}x}{\text{Co}}_{x})}_{2}{\text{As}}_{2}$. From the magnetic field penetration depth $\ensuremath{\lambda}$ we find that for optimally overdoped samples, $1/\ensuremath{\lambda}{(T\ensuremath{\rightarrow}0)}^{2}$ varies monotonically with superconducting transition temperature...
We report elastic and inelastic neutron-scattering measurements of the high-${T}_{\mathrm{C}}$ ferromagnet ${\mathrm{Mn}}_{1+\ensuremath{\delta}}\mathrm{Sb}$. Measurements were performed on a large, ${T}_{\mathrm{C}}=434$ K, single crystal with an interstitial Mn content $\ensuremath{\delta}\ensuremath{\approx}0.13$. The neutron-diffraction results reveal that has magnetic moment, it is aligned antiparallel to main moment. perform density functional theory calculations including find be...
We have performed magnetic susceptibility, heat capacity, muon spin relaxation, and neutron-scattering measurements on three members of the family ${\mathrm{Ba}}_{3}M{\mathrm{Ru}}_{2}{\mathrm{O}}_{9}$, where $M\phantom{\rule{0.16em}{0ex}}=\phantom{\rule{0.16em}{0ex}}\mathrm{In}$, Y, Lu. These systems consist mixed-valence Ru dimers a triangular lattice with antiferromagnetic interdimer exchange. Although previous work has argued that charge order within or intradimer double exchange plays an...
We present a comprehensive neutron scattering study of the breathing pyrochlore magnet LiGaCr4S8. observe an unconventional magnetic excitation spectrum with separation high- and low-energy spin dynamics in correlated paramagnetic regime above spin-freezing transition at 12(2) K. By fitting to diffuse-scattering data, we parametrize Hamiltonian. find that interactions are ferromagnetic within large small tetrahedra lattice, but antiferromagnetic further-neighbor also essential explain our...