Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects

Oxygen Vacancy Engineering for Highly Tunable Ferromagnetic Properties: A Case of SrRuO(3)Ultrathin Film with a SrTiO(3)Capping Layer

© 2020 Wiley-VCH GmbH. Oxide heterostructures have great potential for spintronics applications due to their well-defined heterointerfaces and vast functionalities. To integrate such compelling features into practical spintronics devices, effective control of the magnetic switching behavior is key. Here, continuous control of the magnetic coercive field in SrTiO3/SrRuO(3)ultrathin heterostructures is achieved by oxygen vacancy (V-O) engineering. Pulsed laser deposition of an oxygen-deficient SrTiO(3)capping layer can trigger V(O)migration into the SrRuO(3)layer while avoiding the formation of Ru vacancies. Moreover, by varying the thickness and growth conditions of the SrTiO(3)capping layer, the value of the coercive field (H-C) in the ferromagnetic SrRuO(3)layer can be continuously tuned. The maximum enhancement ofH(C)at 5 K is 3.2 T. Such a wide-range tunability ofH(C)may originate from a V-O-induced enhancement of perpendicular magnetic anisotropy and domain wall pinning. This study offers effective approaches for controlling physical properties of oxide heterostructures via V(O)engineering, which may facilitate the development of oxide-based functional devices11sciescopu