[en] We have investigated the magnetic and transport properties of a noncentrosymmetric compound PrRhSi₃ by dc magnetic susceptibility χ(T), isothermal magnetization M(H), thermoremanent magnetization M(t), specific heat C_p(T), electrical resistivity ρ(T,H) and muon spin relaxation (μSR) measurements. At low fields χ(T) shows two anomalies near 15 and 7 K with an irreversibility between ZFC and FC data below 15 K. In contrast, no anomaly is observed in C_p(T) or ρ(T) data. M(H) data at 2 K exhibit very sharp increase below 0.5 T and a weak hysteresis. M(t) exhibits very slow relaxation, typical for a spin-glass system. Even though the absence of any anomaly in C_p(T) is consistent with the spin-glass type behavior, there is no obvious origin of spin-glass behavior in this structurally well ordered compound. The crystal electric field (CEF) analysis of C_p(T) data indicates a CEF-split singlet ground state lying below a doublet at 81(1) K and a quasi-triplet at 152(2) K. The ρ(T) data indicate a metallic behavior, and ρ(H) exhibits a very high positive magnetoresistance, as high as ∼300% in 9 T at 2 K. No long range magnetic order or spin-glass behavior was detected in a μSR experiment down to 1.2 K. (paper)

[en] Zero field μSR has been used to probe rare earth spin dynamics in the magnetic superconductors, Y_1-xEr_xNi₂B₂C. The muon spin relaxation function is stretched exponential, exp (-(λt)^β), in form, as usually found for spin glass systems above the glass temperature. However, the Y_1-xEr_x Ni₂B₂C compounds show no evidence of coexisting superconducting and static spin glass ground states even at concentrations below the critical value (x=0.6) for long range antiferromagnetic order. The temperature dependence of both the muon spin relaxation rate λ and the exponent β suggests that Er spin dynamics change significantly at the superconducting transition temperature.

[en] Longitudinal and transverse field muon spin rotation/relaxation measurements have been carried out on a polycrystalline sample of ThPt₄Ge₁₂. The zero-field measurements in the longitudinal geometry do not reveal any signature of a spontaneous internal magnetic field below the superconducting transition temperature, indicating the preservation of time-reversal symmetry in the superconducting state of ThPt₄Ge₁₂. From the transverse field data, the zero field magnetic penetration depth, λ(0), was estimated to be 110(15) nm, and then we have estimated the effective mass of the quasiparticles, m*∼4.5m_e, and the superfluid carrier density, n_s∼1.06 x 10²⁸ carriers m^-3. We found a marked difference between the zero-field cooling and field-cooled vortex state muon spin relaxation rates, σ_s(T), below the irreversibility temperature, T_ir ∼ 2.5 K. A linear field dependence of σ_s(H) and power law behaviour of σ_s(T) exhibit a significant deviation from those expected for isotropic BCS-superconductors. The analysis of correlation between the superconducting transition temperature and the effective Fermi temperature within the Uemura classification scheme reveals that the condensation energy in ThPt₄Ge₁₂ is comparable to those of exotic superconductors.

[en] The noncentrosymmetric superconductor TaOs has been characterized using x-ray diffraction, resistivity, magnetization, and specific heat measurements. Magnetization and specific heat measurements show a bulk superconducting transition at 2.07 K. These measurements suggest that TaOs is a weakly coupled type-II superconductor. The electronic specific heat in the superconducting state can be explained by the single-gap BCS model, suggesting s-wave superconductivity in TaOs. (paper)

[en] Noncentrosymmetric superconductors can lead to a variety of exotic properties in the superconducting state such as line nodes, multigap behavior, and time-reversal symmetry breaking. In this paper, we report the properties of a new noncentrosymmetric superconductor TaOs, using muon spin relaxation and rotation measurements. It is shown using the zero-field muon experiment that TaOs preserve the time-reversal symmetry in the superconducting state. From the transverse field muon measurements, we extract the temperature dependence of , which is proportional to the superfluid density. This data can be fit with a fully gapped s-wave model for   =  2.01 0.02. Furthermore, the value of magnetic penetration depth is found to be 5919 45 , which is consistent with the value obtained from the bulk measurements. (paper)

[en] We report the magnetic and transport properties of a new ternary intermetallic compound, CeRhSn₃, using magnetic susceptibility, magnetization, specific heat, electrical resistivity, muon-spin relaxation (μSR) and neutron diffraction investigations. The dc magnetic susceptibility data reveal two magnetic phase transitions at 0.9 and 4 K. The overall behavior of dc susceptibility and magnetization indicates a ferrimagnetic-type phase transition near 4 K. The specific heat data also exhibit sharp λ-type anomalies at 1 and 4 K. The behavior of the specific heat anomaly under the application of a magnetic field suggests that the 1 K transition is probably related to a transition from a ferri- to a ferromagnetic state. The low temperature specific heat exhibits an enhanced Sommerfeld coefficient γ (∼100 mJ mol^-1 K^-2) due to the formation of a moderate heavy fermion state. The resistivity of CeRhSn₃ demonstrates an interplay between the RKKY and Kondo interactions which is further modified by the presence of the crystal electric field. Interestingly, the resistivity of the nonmagnetic reference compound, LaRhSn₃, is found to increase with decreasing temperature. Further, the onset of long-range magnetic order below 1 K is confirmed from our μSR study on CeRhSn₃. However, the 4 K transition is not detected in the μSR and low temperature neutron diffraction data. Analysis of the dc magnetic susceptibility data within the framework of a two-sublattice model of ferrimagnetism supports the ferrimagnetic-type transition at 4 K in CeRhSn₃. We have observed an unusual frequency dependence of the peak near 4 K in the ac susceptibility, which shows that the transition temperature shifts toward the lower temperature side with increasing frequency.

[en] We report our comprehensive study of physical properties of a ternary intermetallic compound PrIrSi₃ investigated by dc magnetic susceptibility χ(T), isothermal magnetization M(H), thermo-remnant magnetization M(t), ac magnetic susceptibility χ_ac(T), specific heat C_p(T), electrical resistivity ρ(T), muon spin relaxation (µSR) and inelastic neutron scattering (INS) measurements. A magnetic phase transition is marked by a sharp anomaly at T_tr = 12.2 K in χ(T) measured at low applied fields which is also reflected in the C_p(T) data through a weak anomaly at 12 K. An irreversibility between the zero field cooled and field cooled χ(T) data below 12.2 K and a very large relaxation time of M(t) indicates the presence of ferromagnetic correlation. The magnetic part of specific heat shows a broad Schottky-type anomaly near 40 K due to the crystal electric field (CEF) effect. An extremely small value of magnetic entropy below 12 K suggests a CEF-split singlet ground state which is confirmed from our analysis of INS data. The INS spectra show two prominent inelastic excitations at 8.5 meV and 18.5 meV that could be well accounted by a CEF model. The CEF splitting energy between the ground state singlet and the first excited doublet is found to be 92 K. Our µSR data reveal a possible magnetic ordering below 30 K, which is much higher than that found from the specific heat and magnetic susceptibility measurements. This could be due to the presence of short range correlations well above the long range magnetic ordering or due to the electronic changes induced by muons. The induced moment magnetism in the singlet ground state system PrIrSi₃ with such a large splitting energy of 92 K is quite surprising. (paper)

[en] NbRh₂B₂ crystallises in a chiral noncentrosymmetric structure and exhibits bulk type-II superconductivity below K. Here we show that the temperature dependence of the upper critical field deviates from the behaviour expected for both Werthamer–Helfand–Hohenberg and the Ginzburg–Landau models and that T exceeds the Pauli paramagnetic limit, T. We explore the reasons for this enhancement. Transverse-field muon spectroscopy measurements suggest that the superconducting gap is either s-wave or -wave, and the pressure dependence of reveals the superconducting gap is primarily s-wave in character. The magnetic penetration depth nm. Heat capacity measurements reveal the presence of a multigap -wave superconducting order parameter and moderate electron–phonon coupling. (paper)

[en] Using muon spin relaxation (μSR) and inelastic neutron scattering (INS) we have investigated the normal state of the superconductor Mo₃Sb₇ and the reference compound Ru₃Sn₇. The μSR experiments on Ru₃Sn₇ reveal static and relatively slow dynamic relaxations, which are ascribed to a random static nuclear dipole field and thermally activated muon motion, respectively. INS experiments on Ru₃Sn₇, on the other hand, reveal three phononic excitations at 11, 18 and 23 meV, substantiating the assertion of Einstein and Debye oscillations derived from the specific heat and electrical resistivity data. The distinct difference in the μSR as well as INS spectra between Ru₃Sn₇ and Mo₃Sb₇ provides strong evidence for a magnetic/electronic nature of the phase transition at T^* = 50 K in the Mo-based compound. On the basis of the μSR and INS data, the energy spin pseudogap of 150(10) K was estimated. The observed weak magnetism in the dynamic susceptibility χ^''(Q,ω) and residual longitudinal field relaxation at 5 K imply a static ordering or quantum fluctuations.

[en] The geometrical frustration of the β-Mn lattice suppresses moment formation, leading to a spin-liquid ground state. Alloying β-Mn to expand the unit cell results in moment localization, but the resulting ground state is normally a spin glass. However, alloys of β-Mn with Ru and Os were found to exhibit long-range order. This paper reports a study of the low-frequency spin dynamics in β-MnRu alloys using muon spin relaxation, supported by susceptibility, heat capacity and neutron diffraction data. For Ru concentrations ≤9 at.%, spin-glass ground states are found. Antiferromagnetism is found at higher concentrations, but at low temperatures there is evidence for a coexistent spin-glass state