No abstract

We report results of magnetization, specific heat, and muon spin relaxation (μSR) measurements on single crystals of disorder-free Yb 3+ triangular lattice Yb(BaBO 3 ) 3 . The magnetization experiments show anisotropic magnetic properties with Curie-Weiss temperatures θ ⊥ = −1.40 K (H ⊥ c) and θ = −1.16 K (H c) determined from low-temperature data. The absence of both long-range antiferromagnetic order and spin freezing is confirmed down to 0.27 K at zero field. A two-level Schottky anomaly due to the opening of the ground-state Kramers doublet is observed from the low-temperature specific heat measurements when the applied magnetic fields μ 0 H > 0.7 T. At zero field, the increase of both C mag /T and the muon spin relaxation rate λ below 1 K is due to the electronic spin excitations, which often exist in quantum magnets where dipole-dipole interactions create an anisotropy of magnetic properties. The spin excitation is also supported by the unusual maximum of the field dependence of λ due to the field-induced increase in the density of excitations. We argue that dipolar interaction is dominant and induces the spin dynamics in the quantum magnet Yb(BaBO 3 ) 3 .

We report the results of muon spin rotation and relaxation (μSR) measurements on the recently discovered layered Cu-based superconducting material La 2 (Cu 1−x Ni x ) 5 As 3 O 2 (x = 0.40 and 0.45). Transverse-field μSR experiments on both samples show that the temperature dependence of superfluid density is best described by a two-band model. The absolute values of zero-temperature magnetic penetration depth λ ab (0) were found to be 427(1.7) and 422(1.5) nm for x = 0.40 and 0.45, respectively. Both compounds are located between the unconventional and the standard BCS superconductors in the Uemura plot. No evidence of time-reversal symmetry breaking in the superconducting state is suggested by zero-field μSR measurements.