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We have investigated the noncentrosymmetric tetragonal heavy fermion compound CeAuAl3 using muon spin rotation (μSR), neutron diffraction (ND), and inelastic neutron scattering (INS) measurements. We have also revisited the magnetic, transport, and thermal properties. The magnetic susceptibility reveals an antiferromagnetic transition at 1.1 K with, possibly, another magnetic transition near 0.18 K. The heat capacity shows a sharp λ-type anomaly at 1.1 K in zerofield, which broadens and moves to a higher temperature in an applied magnetic field. Our zero-field μSR and ND measurements confirm the existence of a long-range magnetic ground state below 1.2 K. Further, the ND study reveals an incommensurate magnetic order with a magnetic propagation vector k=(0,0,0.52(1)) and a spiral structure of Ce moments coupled ferromagnetically within the ab plane. Our INS study reveals the presence of two well-defined crystal electric field (CEF) excitations at 5.1 and 24.6 meV in the paramagnetic phase of CeAuAl3 that can be explained on the basis of the CEF theory and the Kramer's theorem for a Ce ion having a 4f1 electronic state. Furthermore, low energy quasielastic excitations show a Gaussian line shape below 30 K compared to a Lorentzian line shape above 30 K, indicating a slowdown of spin fluctuations below 30 K. We have estimated a Kondo temperature of TK=3.5K from the quasielastic linewidth, which is in good agreement with that estimated from the heat capacity. This study also indicates the absence of any CEF-phonon coupling unlike that observed in isostructural CeCuAl3 The CEF parameters, energy level scheme, and their wave functions obtained from the analysis of INS data explain satisfactorily the single crystal susceptibility in the presence of two-ion anisotropic exchange interaction in CeAuAl3. [ABSTRACT FROM AUTHOR]

The magnetic states of the noncentrosymmetric pressure-induced superconductor CeCoGe3 have been studied with magnetic susceptibility, muon spin relaxation (μSR), single-crystal neutron diffraction, and inelastic neutron scattering (INS). CeCoGe3 exhibits three magnetic phase transitions at TN1=21,TN2=12, and TN3=8K. The presence of long-range magnetic order below TN1 is revealed by the observation of oscillations of the asymmetry in the μSR spectra between 13 and 20 K and a sharp increase in the muon depolarization rate. Single-crystal neutron-diffraction measurements reveal magnetic Bragg peaks consistent with propagation vectors of k=(0,0,23) between TN1 and TN2,k=(0,0,5/8) between TN2 and TN3 and k=(0,0,½) below TN3. An increase in intensity of the (110) reflection between TN1 and TN3 also indicates a ferromagnetic component in these phases. These measurements are consistent with an equal moment two-up two-down magnetic structure below TN3 with a magnetic moment of 0.405(5)μB/Ce. Above TN2, the results are consistent with an equal moment two-up one-down structure with a moment of 0.360(6)μB/Ce. INS studies reveal two crystal-electric-field (CEF) excitations at ~19 and ~27 meV. From an analysis with a CEF model, the wave functions of the J=5/2 multiplet are evaluated along with a prediction for the magnitude and direction of the ground-state magnetic moment. Our model correctly predicts that the moments order along the c axis, but the observed magnetic moment of 0.405(5)μB is reduced compared to the predicted moment of 1.0μB. This is ascribed to hybridization between the localized Ce3+ f electrons and the conduction band. This suggests that CeCoGe3 has a degree of hybridization between that of CeRhGe3 and the noncentrosymmetric superconductor CeRhSi3. [ABSTRACT FROM AUTHOR]

The magnetic ground state of CeRhGe3 has been investigated using magnetic susceptibility, heat capacity, neutron diffraction, muon spin relaxation (μSR), and inelastic neutron scattering (INS) techniques. Our /μSR study clearly reveals the presence of two frequencies below TN2 = 7 K and three frequencies between 7 K and TN1 = 14.5 K, indicating long-range magnetic ordering of the Ce3+ moment. The temperature dependence of the highest frequency follows a mean-field order parameter. Our powder neutron diffraction study at 1.5 K reveals the presence of magnetic Bragg peaks, indexed by the propagation vector k = (0, 0, 3/4) with the Ce3+ magnetic moment ∼0.45(9)μB along the c axis. INS studies at 18 K (i.e., above TNi ) show the presence of two well-defined crystal-field (CEF) excitations at 7.5 and 18 meV. At 10 and 4.5 K, a very small increase has been observed in the CEF excitation energies. At 100 K, both CEF excitations broaden and a broad quasielastic component has also been observed. Further, the low-energy INS study reveals the presence of a nearly temperature-independent quasielastic linewidth between 16 and 60 K, which indicates a Kondo temperature TK = 12.6(3) K. The presence of well-defined CEF excitations in CeRhGe3 suggests local moment magnetism and may explain the absence of pressure-induced superconductivity. Analyzing the INS data based on a CEF model, we have evaluated the CEF ground-state wave functions and ground-state moment. The observed small value of the ordered moment along the c axis, deduced from the neutron diffraction data, contrasts with the ab-plane moment direction predicted by the single-ion CEF anisotropy and indicates the presence of two-ion anisotropic magnetic exchange interactions, which govern the direction of the moment. [ABSTRACT FROM AUTHOR]

The temperature dependence of the generalized phonon density of states (GDOS) of polycrystalline Mo3Sb7 and Mo3Sb5,4Te1,6 was studied from 300 K down to 2 K using inelastic neutron scattering. Even though Mo3Sb7 undergoes a magnetic as well as a structural phase transition at T* = 53 K, no appreciable change in the recorded spectra has been revealed. The generalized density of states of the nonmagnetic Mo3Sb5,4Te1,6 compound shows similar main characteristics, though substituting Sb by Te leads to a shift of the entire spectrum towards higher energy. The temperature dependence of the GDOS reveals an anomalous softening of phonons with decreasing temperature in Mo3Sb7 which cannot be captured by the harmonic approximation while Mo3Sb5,4Te1,6 exhibits a normal behavior. This feature might be related to a strong interplay between magnetic excitations and phonons at the core of the anomalous thermal transport displayed by Mo3Sb7. In general, the main characteristics of the experimentally derived GDOS of Mo3Sb7can be reproduced by lattice dynamical calculations. [ABSTRACT FROM AUTHOR]

Excitations in a spin ice behave as magnetic monopoles, and their population and mobility control the dynamics of a spin ice at low temperature. CdEr2Se4 is reported to have the Pauling entropy characteristic of a spin ice, but its dynamics are three orders of magnitude faster than the canonical spin ice Dy2Ti2O7. In this Letter we use diffuse neutron scattering to show that both CdEr2Se4 and CdEr2S4 support a dipolar spin ice state--the host phase for a Coulomb gas of emergent magnetic monopoles. These Coulomb gases have similar parameters to those in Dy2Ti2O7, i.e., dilute and uncorrelated, and so cannot provide three orders faster dynamics through a larger monopole population alone. We investigate the monopole dynamics using ac susceptometry and neutron spin echo spectroscopy, and verify the crystal electric field Hamiltonian of the Er3+ ions using inelastic neutron scattering. A quantitative calculation of the monopole hopping rate using our Coulomb gas and crystal electric field parameters shows that the fast dynamics in CdEr2X4(X = Se,S) are primarily due to much faster monopole hopping. Our work suggests that CdEr2X4 offer the possibility to study alternative spin ice ground states and dynamics, with equilibration possible at much lower temperatures than the rare earth pyrochlore examples. [ABSTRACT FROM AUTHOR]

The opening of a spin gap in the orthorhombic compounds Ce T2Al10 (T=RuandOs) is followed by antiferromagnetic ordering at TN=27 and 28.5 K, respectively, with a small ordered moment (0.29-0.34μB) along the c axis, which is not an easy axis of the crystal field (CEF). In order to investigate how the moment direction and the spin gap energy change with La doping in Ce1-xLaxT2Al10 (T = Ru and Os) and also to understand the microscopic nature of the magnetic ground state, we here report on magnetic, transport, and thermal properties, neutron diffraction (ND), and inelastic neutron scattering (INS) investigations on these compounds. Our INS study reveals the persistence of spin gaps of 7 and 10 meV in the 10% La-doped T = Ru and Os compounds, respectively. More interestingly our ND study shows a very small ordered moment of 0.18 μB along the b axis in Ce0.9La0.1Ru2Al10, however a moment of 0.23 μB still along the c axis in Ce0.9La0.1Os2Al10. This contrasting behavior can be explained by a different degree of hybridization in CeRu2Al10 and CeOs2Al10, being stronger in the latter than in the former. Muon spin rotation (μSR) studies on Ce1-xLaxRu2Al10 (x=0, 0.3, 0.5, and 0.7), reveal the presence of coherent frequency oscillations indicating a long-range magnetically ordered ground state for x=0 to 0.5, but an almost temperature independent Kubo-Toyabe response between 45 mK and 4 K for x=0.7. We compare the results of the present investigations with those reported on the electron and hole doping in CeT2Al10. [ABSTRACT FROM AUTHOR]