Zeeman perturbed nuclear quadrupole resonance investigation of orbitally ordered KCuF3

We investigated the electric field gradient tensor at the Cu nuclei by Zeeman perturbed nuclear quadrupole resonance in orbitally ordered KCuF3. Our data show the presence of two inequivalent crystallographic sites with distinct orientations of the copper wave function, compatibly with the proposed orbital order for this compound. An unusual behaviour of the paramagnetic NQR signal at the Néel transition is reported

The Role of CuO Chain Length on Superconductivity Emergence in YBa2Cu3O6.30

The authors investigate the tetragonal(T)-orthorhombic(O) transient zone of YBa2Cu3O6+x, in a comparative way on pair samples one of which is produced by deintercalation [D] and the other by intercalation [I] of intrinsic oxygen in the basal Cu(1)Ox plane and having the same oxygen content (k) and thermal history. Resistive and electron diffraction measurements, performed on [D]k-[I]k pairs within the composition range 0.28 ≤ k ≤ 0.32, are reported. Direct evidence is provided that the T-OII transient is a structural and electronic two phase region characterized by the (T+OII)[D]0.30 non-superconducting (non-SC) and (OII+OIII*)[I]0.30 superconducting (SC) phases. The OII superstructure represents the minority component of [D]0.30 phase and the majority one of [I]0.30 and OIII* is a new orthorhombic anti-OIII superstructure. The nature of the non-SC and SC behaviours has been comparatively investigated by NQR analysis at the T-OII borderline. The evaluated different values of the average chain lengths emphasize the role of the Cu-O chain length on the hole doping efficiency in YBCO at constant oxygen content

The Role of CuO Chain Length on Superconductivity Emergence in YBa2Cu3O6.30

The authors investigate the tetragonal(T)-orthorhombic(O) transient zone of YBa2Cu3O6+x, in a comparative way on pair samples one of which is produced by deintercalation [D] and the other by intercalation [I] of intrinsic oxygen in the basal Cu(1)Ox plane and having the same oxygen content (k) and thermal history. Resistive and electron diffraction measurements, performed on [D]k-[I]k pairs within the composition range 0.28 ≤ k ≤ 0.32, are reported. Direct evidence is provided that the T-OII transient is a structural and electronic two phase region characterized by the (T+OII)[D]0.30 non-superconducting (non-SC) and (OII+OIII*)[I]0.30 superconducting (SC) phases. The OII superstructure represents the minority component of [D]0.30 phase and the majority one of [I]0.30 and OIII* is a new orthorhombic anti-OIII superstructure. The nature of the non-SC and SC behaviours has been comparatively investigated by NQR analysis at the T-OII borderline. The evaluated different values of the average chain lengths emphasize the role of the Cu-O chain length on the hole doping efficiency in YBCO at constant oxygen content

Proximity effects induced by a gold layer on La0.67Sr0.33MnO3 thin films

We report about La0.67Sr0.33MnO3 single crystal manganite thin films in interaction with a gold capping layer. With respect to uncoated manganite layers of the same thickness, Au-capped 4 nm-thick manganite films reveal a dramatic reduction (about 185 K) of the Curie temperature TC and a lower saturation low-temperature magnetization M0. A sizeable TC reduction (about 60 K) is observed even when an inert SrTiO3 layer is inserted between the gold film and the 4 nm-thick manganite layer, suggesting that this effect might have an electrostatic origin

Production of pulsed ultra slow muons and first μSR experiments on thin metallic and magnetic films

At ISIS, RAL (UK) we have produced a pulsed ultra-slow muon beam (E≤20 eV) and performed the first μSR experiments. Thanks to the pulsed feature, the implantation time is automatically determined and, by adjusting the final muon energy between approximately 8 keV and 20 eV, depth slicing experiments are possible down to monolayers distances. We report slicing experiments across a 20 nm copper film on quartz substrate with evidence for a 2 nm copper oxide surface layer. A preliminary experiment on a hexagonal cobalt film suggests the existence of muon precession in the local magnetic field

Multi-messenger Observations of a Binary Neutron Star Merger

International audienceOn 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of $\sim 1.7\,{\rm{s}}$ with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg(2) at a luminosity distance of ${40}_{-8}^{+8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 $\,{M}_{\odot }$. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at $\sim 40\,{\rm{Mpc}}$) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position $\sim 9$ and $\sim 16$ days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta