Nonunitary triplet pairing in the centrosymmetric superconductor LaNiGa2.

Muon spin rotation and relaxation experiments on the centrosymmetric intermetallic superconductor LaNiGa2 are reported. The appearance of spontaneous magnetic fields coincides with the onset of superconductivity, implying that the superconducting state breaks time reversal symmetry, similarly to noncentrosymmetric LaNiC2. Only four triplet states are compatible with this observation, all of which are nonunitary triplets.

A neutron polarization analysis study of moment correlations in (Dy(0.4)Y(0.6))T(2) (T = Mn, Al).

We present a study of the magnetic moment correlations of two pseudo-binary C15 Laves phase compounds, (Dy(0.4)Y(0.6))Mn(2) and (Dy(0.

Generalized spin-glass relaxation.

Spin relaxation close to the glass temperature of CuMn and AuFe spin glasses is shown, by neutron spin echo, to follow a generalized exponential function which explicitly introduces hierarchically constrained dynamics and macroscopic interactions. The interaction parameter is directly related to the normalized Tsallis nonextensive entropy parameter q and exhibits universal scaling with reduced temperature. At the glass temperature q=5/3 corresponding, within Tsallis' q statistics, to a mathematically defined critical value for the onset of strong disorder and nonlinear dynamics.

Evidence for time-reversal symmetry breaking in the noncentrosymmetric superconductor LaNiC2.

Muon spin relaxation experiments on the noncentrosymmetric intermetallic superconductor LaNiC2 are reported. We find that the onset of superconductivity coincides with the appearance of spontaneous magnetic fields, implying that in the superconducting state time-reversal symmetry is broken. An analysis of the possible pairing symmetries suggests only four triplet states compatible with this observation, all of them nonunitary.

Magnetic short-range order in β-Mn(1-x)Co(x).

We present a study of the magnetic ground state properties of β-Mn metal alloyed with Co, using neutron polarization analysis of the diffuse neutron scattering cross-section. We analyse the magnetic structure obtained using a reverse Monte Carlo procedure to extract the Mn-Mn spin correlations. The addition of Co leads to a static disordered magnetic structure with medium-range correlations.