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Abstract: Zero-field SR has been used to probe the Er spin dynamics in superconducting (, 0.05 and 0.1). At all temperatures the magnetic muon spin relaxation is described by a root exponential function. Above approximately the temperature dependence of the associated muon spin relaxation rate, , is Arrhenius in form whilst below this temperature becomes temperature independent suggesting that the Er spin dynamics undergo a sharp cross-over from thermally activated behaviour above (with ) to a quantum tunnelling regime below . [Copyright &y& Elsevier]

Abstract: Inelastic neutron scattering measurements have been carried out to investigate the crystal field (CF) excitations of in order to understand the mechanisms of the quadrupolar ordering () observed at 24.7K. Our analysis shows that the ground state is made up of nearly degenerate two Kramer doublets forming a ‘quasi-quartet’ ground state. This is consistent with heat capacity measurements, which have shown an estimated entropy of at (15.3K) and an additional at . A considerable shift and change in the width of the CF excitations and the splitting of the quasi-quartet ground state into two well-resolved doublets below as well as a Zeeman splitting below have also been observed. [Copyright &y& Elsevier]

Abstract: Inelastic neutron scattering measurements have been carried out to investigate the crystal field (CF) excitations of CeB2C2. The crystal field excitations have large energy widths, indicating strong hybridization between the localized 4f electrons and the conduction electrons. The analysis of the data, based on a crystal field model, gives good agreement with both the measured heat capacity and the saturation magnetization at low temperatures. [Copyright &y& Elsevier]

Abstract: Muon measurements have been carried out to probe the magnetic correlations within DyB2C and HoB2C. These measurements confirm the presence of two independent magnetic processes in DyB2C and HoB2C. The onset of the correlations corresponding to the magnetic random layer phase occurred at higher critical temperatures than expected from neutron diffraction experiments. [Copyright &y& Elsevier]

Abstract: The magnetic ground-state of the pyrochlore material Hg2Ru2O7, which undergoes a metal to Mott insulator transition (MIT) at T=107K, was investigated using muon spin relaxation and neutron powder diffraction (both non-polarized and polarized) measurements. Unlike the expected behavior associated with a spin-singlet ground-state, these surprisingly revealed the onset of long-range magnetic ordering below the MIT. [Copyright &y& Elsevier]

Abstract: A paramagnetic muonium centre is detected in elemental boron at cryogenic temperatures and characterized by hyperfine decoupling in longitudinal magnetic fields. The contact term is only 0.52GHz or 12% of the free muonium value. An effective ionization energy of 0.1eV is estimated from polarization transfer to the muon Larmor precession signal in transverse field, beginning around 100K and complete by room temperature. AIMPRO density functional calculations identify candidate sites for monatomic hydrogen defect centres in the rather complex boron lattice and predict the local distribution of unpaired electron spin density. One of these, bridging between two boron atoms in the inter-icosahedral space, provides an adequate match to the muonium hyperfine parameters, as well as its relatively weak binding energy. Negative-U behaviour is predicted, implying that centres are not thermodynamically stable. Identification of the high diamagnetic muon fraction found at all temperatures is also discussed. [Copyright &y& Elsevier]

Abstract: High-resolution neutron-powder diffraction data show that the double perovskite Ba2PrIrO6 is cubic at ambient temperatures in space group Fm m. Below T N=71K the compound orders antiferromagnetically with magnetic moments of ∼0.43(2) μ B at 6K, on both the Pr4+ and the Ir4+ sites, oriented along the cubic a-axis. Inelastic neutron scattering at 105K reveals a strong peak at ∼276meV and a weak transition at 366meV. The former is consistent with the crystal field splitting of the Pr4+ ground state under the cubic point symmetry, while the latter peak is due to the intermultiplet transition between the ground state and excited state. [Copyright &y& Elsevier]

Abstract: The compounds RMn4Al8 are characterized by very weak magnetic interactions between the rare earth (R) sites and the Mn sites. The Mn sites form one-dimensional chains and it likely that this inhibits moment formation and leads to low frequency spin fluctuations. ZF-μSR studies show similar behaviour in all four compounds with , Dy, Ho and Er. The relaxation spectrum has two components: the slow relaxation rate peaks below the temperature where the ZFC susceptibility has a cusp, associated with ordering of the Mn moments. The second component has a high relaxation rate that increases rapidly at low temperatures. We tentatively attribute this to the slowing down of the rare earth spin dynamics. [Copyright &y& Elsevier]

Abstract: Yamasaki et al. (Solid State Commun. 119 (2001) 415) have suggested that LaMn4Al8 is a nearly antiferromagnetic metal with linear chains of Mn atoms. We present evidence from ZF-μSR measurements that both LaMn4Al8 and the related compound PrMn4Al8 display antiferromagnetic order at low temperatures. In LaMn4Al8 the μSR relaxation rate rises to a peak at 4.5K; below this temperature the asymmetry decreases smoothly. In PrMn4Al8 well-defined oscillations appear below 35K. Neutron crystal field spectroscopy suggests a singlet ground state for the Pr3+ ion, so it is likely that the internal field seen by the muons arises from ordered Mn moments. YMn4Al8 shows no sign of magnetic correlations down to 1.2K. [Copyright &y& Elsevier]

Abstract: The structural, magnetic and thermal properties of Ce2Ge2In have been investigated between 0.36 and 300K. The specific heat exhibits a peak and the AC susceptibility exhibits a weak anomaly at 2K, whereas neutron diffraction does not show any signs of long-range magnetic ordering down to 0.36K. Inelastic neutron scattering at 17K shows two well-defined crystal field (CF) excitations at 11.6 and 20.1meV, indicating a doublet CF ground state of the Ce3+ ion in agreement with the entropy ∼Rln2 at 10K derived from the heat capacity data. [Copyright &y& Elsevier]

Abstract: A new spectrometer (HiFi) is being constructed at the ISIS pulsed muon source. The spectrometer is intended for measurements in longitudinal magnetic fields up to 5T. Here we discuss various aspects of the design and future operation of the HiFi spectrometer. Detailed analysis of the detector design is presented, and results from tests on detector prototypes are compared to simulations. Potential applications of this spectrometer in the fields of condensed matter and chemistry are also discussed. [Copyright &y& Elsevier]

Abstract: We report on unusual non-Fermi liquid features of the ternary compound which exhibits the largest ever recorded value of the electronic specific heat at in a purely paramagnetic system. The latter is confirmed by SR measurements down to 30mK revealing a rather slow simple exponential muon spin depolarisation in zero-field and thus a spatially homogeneous paramagnetic state. The ground state properties and crystal field (CF) splitting of have been studied by specific heat, magnetic susceptibility as well as muon spin relaxation (SR) and inelastic neutron spectroscopy (INS). [Copyright &y& Elsevier]

Abstract: Using muon spin rotation, well-defined bulk magnetic phases in are revealed. A novel magnetic phase is detected for with the highest transition temperature ever observed for . This stresses the diversity of magnetic phases and the link between magnetic and structural degrees of freedom. For , no magnetism is detected as expected for the low spin state of . For the charge-ordered compound, a cascade of transitions is observed below 85K. [Copyright &y& Elsevier]

Abstract: Over-oxidized Delafossites MCuO2+ δ are frustrated antiferromagnets formed by a stacking of alternating M3+ and Cu(1+2 δ )+ planes. Frustration arises from the geometry of the magnetic lattice, which is based on corner sharing triangles. We present here a study of YCuO2.5 and YCuO2.66, both with spin magnetic atoms. μSR data of YCuO2.5, a one-dimensional Δ-chain compound, show dynamical behaviour with no transition to a frozen state down to 100mK. YCuO2.66, which possesses a 2D kagomé-like magnetic lattice, orders at 100K, with an internal magnetic field of about 700G at 5K. Further hole doping is achievable in this compound through Ca2+/Y3+ substitution. We show that only 1% Ca doping strongly reduces the transition temperature to 80K. [Copyright &y& Elsevier]

Abstract: A study of the spin dynamics of the archetypes of the highly frustrated magnets, and , is summarized. Especially, low dilutions of the magnetic network could be achieved and we take advantage of the close similarity between these kagome bilayers to single out their typical properties. The phenomenological model for the relaxation, based on sporadic dynamics due to spin excitations in a singlet sea, proposed by Uemura et al., is extended to all fields, temperature and defects range. Its connection to a RVB picture is discussed. [Copyright &y& Elsevier]

Abstract: We have determined the crystal field potential of the superconductor PrRu4Sb12 using inelastic neutron scattering. The ground state of the Pr+3 ions in T h point group symmetry is a singlet with a triplet at an energy of Δ∼5.6meV. Comparison with recent results on the PrOs4Sb12 compound, where and Δ∼0.6meV, supports the conjecture that inelastic quadrupolar fluctuations (or aspherical Coulomb scattering) are responsible for the strong enhancement of . In PrRu4Sb12, the effect is reduced by the higher energy of the first excited level. [Copyright &y& Elsevier]