A5016744199- Muon and positron interactions and applications
- Physics of Superconductivity and Magnetism
- Rare-earth and actinide compounds
- Graphene research and applications
- Advanced Condensed Matter Physics
- Advancements in Battery Materials
- Magnetic and transport properties of perovskites and related materials
- Magnetic Properties of Alloys
- Iron-based superconductors research
- Particle accelerators and beam dynamics
- Ammonia Synthesis and Nitrogen Reduction
- Advanced NMR Techniques and Applications
- Inorganic Chemistry and Materials
- Particle Detector Development and Performance
- Superconductivity in MgB2 and Alloys
- High-pressure geophysics and materials
- Magnetic properties of thin films
- Superconducting Materials and Applications
- Hydrogen Storage and Materials
- Crystallography and Radiation Phenomena
- Neutrino Physics Research
- Boron and Carbon Nanomaterials Research
- Semiconductor materials and interfaces
- Fullerene Chemistry and Applications
- Fusion materials and technologies
TRIUMF
2009-2024
Trimble (Germany)
2012
University of British Columbia
1992-2009
Texas Tech University
1992-2007
University of Alberta
2005-2007
University of Oxford
1996
Rice University
1991-1995
ETH Zurich
1987-1994
University of Saskatchewan
1992-1993
Board of the Swiss Federal Institutes of Technology
1988-1993
Zero-field muon-spin-resonance and lower-critical-field data are presented for a wide range of Th concentrations in ${\mathrm{U}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Th}}_{\mathit{x}}$${\mathrm{Be}}_{13}$, spanning the region where both superconducting second, lower-temperature phase transition observed. Overall T-x boundaries assigned discussed according to nature lower transition. Arguments associating with possible magnetic (time-reversal--violating) state given.
Positive muons injected into solid ${\mathrm{C}}_{60}$, ${\mathrm{K}}_{4}$${\mathrm{C}}_{60}$, and ${\mathrm{K}}_{6}$${\mathrm{C}}_{60}$ form vacuumlike muonium (${\mathrm{\ensuremath{\mu}}}^{+}$${\mathit{e}}^{\mathrm{\ensuremath{-}}}$) with a (6--12)% probability. Observation of coherent spin precession establishes that all three materials are nonmagnetic nonconducting at low temperatures. From the temperature dependence signals we estimate electronic band gaps in...
Experimental data are presented that show low-energy muons able to cause single event upsets in 65 nm, 45 and 40 nm CMOS SRAMs. Energy deposition measurements using a surface barrier detector characterize the kinetic energy spectra produced by M20B muon beam at TRIUMF. A Geant4 application is used simulate estimate incident on memories. Results indicate sensitivity this mechanism will increase for scaled technologies.
Zero- and longitudinal-field muon-spin-relaxation measurements on a heavy-fermion system ${\mathrm{CeCu}}_{2.1}$${\mathrm{Si}}_{2}$ have revealed an onset of static magnetic ordering below ${T}_{M}$\ensuremath{\sim}0.8 K, which coexists with superconductivity ${T}_{C}$=0.7 K. The line shapes the observed muon spin depolarization functions suggest in either spin-glass or incommensurate spin-density-wave states, small averaged moment order 0.1${\ensuremath{\mu}}_{B}$ per formula unit at...
The results of zero-, transverse-, and longitudinal-field muon-spin rotation measurements in polycrystalline Ce${\mathrm{Al}}_{3}$ are reported. They provide evidence for static magnetic correlations below 2 K. From the magnitude local field at muon site it was estimated that effective ${\mathrm{Ce}}^{3+}$ moments may be order 0.05${\mathrm{\ensuremath{\mu}}}_{\mathrm{B}}$. appear as a spatially inhomogeneous phenomenon, partly coherent 0.7 No cooperative phase transition is found.
The dynamics of transitions among muonium (Mu) states in Si have been studied by radio-frequency (rf) muon-spin-resonance techniques. A total ten samples doped to roughly ${10}^{15}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ p type and ${10}^{16}$ n were investigated at temperatures from 10 500 K. normalized rf asymmetry for the ionized center p-type is well described a three-state strong-collision model involving ${\mathrm{Mu}}_{\mathrm{BC}}^{+}$, ${\mathrm{Mu}}_{\mathrm{BC}}^{0}$,...
The molecular dynamics and electronic structure of the ${\mathrm{\ensuremath{\mu}}}^{+}$-${\mathrm{C}}_{60}$ radical in crystalline ${\mathrm{C}}_{60}$ have been studied using muon spin rotation relaxation. At room temperature appears to be a state quasifree rotation. critical ${\mathit{T}}_{\mathit{S}}$=260 K local change discontinuously as expected for first-order phase transition. correlation times reorientation are remarkably close those determined by recent NMR experiments on...
We report measurements on the dynamics of negatively charged muonium ( ${\mathrm{Mu}}^{\ensuremath{-}}$) from 295 to 1000 K in heavily doped n-type GaAs:Si. The ${\mathrm{Mu}}^{\ensuremath{-}}$ center begins diffuse above $500\mathrm{K}$ with a hop rate described by an Arrhenius function $\ensuremath{\nu}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}{\ensuremath{\nu}}_{0}{e}^{{\ensuremath{-}E}_{\ensuremath{\mu}}/{k}_{B}T}$ where...
Zero-field positive muon-spin relaxation rates in ${\mathrm{U}}_{0.965}$${\mathrm{Th}}_{0.035}$${\mathrm{Be}}_{13}$ provide definitive evidence for the onset of magnetic correlations at lower phase transition temperature ${T}_{c2}$ below normal-superconducting ${T}_{c1}$. The is found to be second order and mean field like, with a moment (${10}^{\mathrm{\ensuremath{-}}3}$--${10}^{\mathrm{\ensuremath{-}}2}$)${\ensuremath{\mu}}_{B}$/f atom. Candidates phase, such as superconducting states, are...
The magnetic screening and flux distribution within a polycrystalline sample of La1.85Sr0.15CuO4 has been measured by means muon spin rotation spectrocopy (μSR) between 7.6 K Tc = 34 in applied fields 10 Oe to 2 kOe. Above 500 the transverse field relaxation rate μ+ polarization is quasi-field-independent, as expected for superconducting material mixed state. At low field, clear reduction observed, interpreted disappearance However, average internal at sites, deduced from Larmor frequency...
We report muon spin rotation measurements in $n$-type silicon from 10 to 310 K electric fields up 5 kV/cm. These experiments reveal the nature of partition neutral muonium centers into normal $({\mathrm{Mu}}_{T}^{0})$ and anomalous $({\mathrm{Mu}}_{\mathrm{BC}}^{0})$: Formation ${\mathrm{Mu}}_{T}^{0}$ is consistent with epithermal processes prior thermalization, while ${\mathrm{Mu}}_{\mathrm{BC}}^{0}$ formed via electron transport a thermalized positive muon. The spatial distribution excess...
Muon level-crossing resonance and muon-spin-rotation measurements on heavily doped n-type GaAs:Si GaAs:Te show that the majority of positive muons implanted at room temperature form an isolated diamagnetic muonium center located a high-symmetry site with Ga neighbors along 〈111〉 direction(s). These experiments, together theoretical considerations, imply negatively charged is or near tetrahedral interstitial four nearest-neighbor atoms. Except for zero-point energy differences, these results...
Zero-, transverse-, and longitudinal-field muon-spin-rotation (${\ensuremath{\mu}}^{+}$SR) spectroscopy was performed on polycrystalline ${\mathrm{CeAl}}_{3}$. The onset of frustrated quasistatic magnetic correlations below about 2 K, becoming partly coherent 0.7 detected. occurrence different components in the ${\ensuremath{\mu}}^{+}$SR signal with relative strengths showing a pronounced temperature dependence leads to conclusion that these develop spatially inhomogeneous, way. No evidence...
A paramagnetic muonium (Mu) state with an extremely small hyperfine parameter was observed for the first time in single-crystalline GaN below 25 K. It has a highly anisotropic structure axial symmetry along [0001] direction, suggesting that it is located either at nitrogen-antibonding or bond-centered site oriented parallel to c-axis. Its ionization energy (=< 14 meV) and (--10^{-4} times vacuum value) indicate one of its possible sites produces shallow state, raising possibility analogous...
Muonium defect centers in ultrapure germanium show evidence of cyclic charge-state transitions above approximately 220 K. Detailed analysis the magnetic-field and temperature dependences longitudinal muon spin depolarization rates reveals contributions from both bond-centered tetrahedral cage-centered interstitial ${\mathrm{Mu}}^{0}$ species involved separate ionization/capture charge cycles. An additional diamagnetic state, observed as a nonrelaxing fraction, is identified muonium bound...
Temperature-dependent diamagnetic amplitudes from radio-frequency muon spin-resonance data on two moderately to heavily doped n-type silicon samples require the presence of ${\mathrm{Mu}}_{T}^{\ensuremath{-}}.$ We determine ${\mathrm{Mu}}_{T}^{\ensuremath{-}}$ ${\mathrm{Mu}}_{T}^{0}$ ionization energy be $0.56\ifmmode\pm\else\textpm\fi{}0.03 \mathrm{eV}$ for silicon, considerably higher than ${\mathrm{Mu}}_{\mathrm{BC}}^{0}$ ${\mathrm{Mu}}_{\mathrm{BC}}^{+}$...
The nuclear hyperfine structure of bond-centered muonium in $^{13}\mathrm{C}$ enriched diamond has been resolved using time-differential transverse-field muon spin rotation. measured nearest-neighbor parameters are compared to theoretical values from a recent ab initio Hartree-Fock type cluster calculation. ratios the and free atom indicate that 92% unpaired electron density resides on two atoms, marked contrast with situation for analogous center Si.
Magnetism of layered cobaltites ${\text{Na}}_{x}{\text{CoO}}_{2}$ with $x=0.6$ and 0.9 has been investigated by a positive muon spin rotation relaxation $({\ensuremath{\mu}}^{+}\text{SR})$ spectroscopy together magnetic susceptibility specific-heat measurements, using single-crystal samples in the temperature range between 250 $1.8\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Zero-field-(ZF-) ${\ensuremath{\mu}}^{+}\text{SR}$ measurements on ${\text{Na}}_{0.9}{\text{CoO}}_{2}$ indicate transition...
We report longitudinal muon-spin-relaxation measurements in intrinsic Si from 350 to 850 K. The data are explained by a two-state model describing alternating charge states of muonium resulting thermally excited electrons. Within this model, the average muon-electron hyperfine parameter neutral state is consistent with at tetrahedral interstitial site. This indicates that highest temperatures measured spends significant time away bond center site, calculated adiabatic potential minimum.
The 1-K phase transition in ${\mathrm{UCu}}_{5}$, showing up specific-heat data within the antiferromagnetic state below ${\mathit{T}}_{\mathit{N}}$\ensuremath{\simeq}15 K, was investigated. Neither average internal fields seen by ${\mathrm{\ensuremath{\mu}}}^{+}$ nor magnetic and nuclear Bragg reflections neutron-diffraction reflect while muon relaxation rates increase drastically 1.2 K. These results are interpreted terms of some additional small-moment order or spin-density-wave...
We use neutron diffraction and muon spin relaxation to study the effect of in-plane uniaxial pressure on antiferromagnetic (AF) orthorhombic phase in BaFe$_2$As$_2$ its Co- Ni-substituted members near optimal superconductivity. In low temperature AF ordered state, necessary detwin crystals also increases magnetic moment, reaching an 11$\%$ increase under 40 MPa for BaFe$_{1.9}$Co$_{0.1}$As$_2$, a 15$\%$ BaFe$_{1.915}$Ni$_{0.085}$As$_2$. observe ordering ($T_N$) about 0.25 K/MPa all...
Experiments reveal muon-polaron complexes in Cr${}_{2}$O${}_{3}$. Similar entities may exist many magnetic insulators and semiconductors, where they can be used as proxies to understand the impact of hydrogen impurities.
Zero-field ${\ensuremath{\mu}}^{+}$ spin-rotation measurements in a ceramic sample of Ho${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ reveal three-dimensional antiferromagnetic order below \ensuremath{\approx}5 K and some incoherent, perhaps two-dimensional, up to 50 diminishing fraction the volume. With increasing temperature, at about 100 mK, Ho moments change their orientation from parallel $c$ axis $a$ axis. The effective moment is...