O. O. Bernal

S29iNMR and Hidden Order inURu2Si2

Below T(N) approximately 17 K the 29Si NMR line in URu2Si2 exhibits a previously unobserved field-independent nearly isotropic contribution to the linewidth, which increases to approximately 12 G as T-->0. We argue that this feature does not arise from static freezing of the U-spin magnetization, but is due to coupling between 29Si spins and a hidden order parameter. We discuss time-reversal symmetry-breaking orbital antiferromagnetism and indirect nuclear spin-spin interactions as possible coupling mechanisms. Further NMR experiments and theoretical calculations are suggested.

Glassy Spin Dynamics in Non-Fermi-Liquid UCu5xPdx, x = 1.0 and 1.5

Local f-electron spin dynamics in the non-Fermi-liquid heavy-fermion alloys UCu5-xPdx, x = 1.0 and 1.5, have been studied using muon spin-lattice relaxation. The sample-averaged asymmetry function G(t) indicates strongly inhomogeneous spin fluctuations and exhibits the scaling G(t,H) = G(t/H(gamma)) expected from glassy dynamics. At 0.05 K gamma(x = 1.0) = 0.35+/-0.1, but gamma(x = 1.5) = 0.7+/-0.1. This is in contrast to inelastic neutron scattering results, which yield gamma = 0.33 for both concentrations. There is no sign of static magnetism approximately greater than 10(-3)(B)/U ion in either material above 0.05 K. Our results strongly suggest that both alloys are quantum spin glasses.

m(+) knight shift measurements in U0.965Th0.035Be13 single crystals

Muon spin rotation ( &mgr;SR) measurements of the temperature dependence of the &mgr;(+) Knight shift in single crystals of U0. 965Th0.035Be13 have been used to study the static spin susceptibility chi(s) below the transition temperatures T(c1) and T(c2). While an abrupt reduction of chi(s) with decreasing temperature is observed below T(c1), chi(s) does not change below T(c2) and remains at a value below the normal-state susceptibility chi(n). In the normal state we find an anomalous anisotropic temperature dependence of the transferred hyperfine coupling between the &mgr;(+) spin and the U 5f electrons.

Disorder, inhomogeneity and spin dynamics in f-electron non-Fermi liquid systems

Muon spin rotation and relaxation (μSR) experiments have yielded evidence that structural disorder is an important factor in many f-electron-based non-Fermi-liquid (NFL) systems. Disorder-driven mechanisms for NFL behaviour are suggested by the observed broad and strongly temperature-dependent μSR (and NMR) linewidths in several NFL compounds and alloys. Local disorder-driven theories (Kondo disorder, Griffiths–McCoy singularity) are, however, not capable of describing the time-field scaling seen in muon spin relaxation experiments, which suggest cooperative and critical spin fluctuations rather than a distribution of local fluctuation rates. A strong empirical correlation is established between electronic disorder and slow spin fluctuations in NFL materials.

Penetration depth, multiband superconductivity, and absence of muon-induced perturbation in superconducting PrOs4Sb12

Transverse-field muon spin rotation

μSR and NMR in f-electron non-Fermi liquid materials

(\text{TF-}\ensuremath{\mu}\text{SR})

Spin dynamics in a structurally ordered non-Fermi liquid compound: YbRh2Si2

experiments in the heavy-fermion superconductor

Suppression of time-reversal symmetry breaking superconductivity in Pr(Os 1 − x Ru x ) 4 Sb 12 and Pr 1 − y La y Os 4 Sb 12

{\text{PrOs}}_{4}{\text{Sb}}_{12}({T}_{c}=1.85\text{ }\text{K})

μSR in Ce1-xLaxAl3: anisotropic Kondo effect?

suggest that the superconducting penetration depth

μ+-Knight shift in the superconducting state of U1−xThxBe13, x=0 and 0.035 single crystals

\ensuremath{\lambda}(T)