247 research outputs found
Epitaxial growth and characterization of (001) [NiFe/M]20 (M = Cu, CuPt and Pt) superlattices
We present optimization of [(15 \uc5) Ni80Fe20/(5 \uc5) M]20 single crystal multilayers on (001) MgO substrates, with M being Cu, Cu50Pt50 and Pt. These superlattices were characterized by high resolution X-ray reflectivity (XRR) and diffraction (XRD) as well as polar mapping of important crystal planes. It is shown that cube on cube epitaxial relationship can be obtained when depositing at substrate temperature of 100 \ub0C regardless of the lattice mismatch (5% and 14% for Cu and Pt, respectively). At lower substrate temperatures poly-crystalline multilayers were obtained while at higher substrate temperatures {111} planes appear at ∼10\ub0 off normal to the film plane. It is also shown that as the epitaxial strain increases, the easy magnetization axis rotates towards the direction that previously was assumed to be harder, i.e. from [110] to [100], and eventually further increase in the strain makes the magnetic hysteresis loops isotropic in the film plane. Higher epitaxial strain is also accompanied with increased coercivity values. Thus, the effect of epitaxial strain on the magnetocrystalline anisotropy is much larger than what was observed previously in similar, but polycrystalline samples with uniaxial anisotropy (Kateb et al. 2021)
Foundations of physical vapor deposition with plasma assistance
Physical vapor deposition (PVD) refers to the removal of atoms from a solid or a liquid by
physical means, followed by deposition of those atoms on a nearby surface to form a thin film
or coating. Various approaches and techniques are applied to release the atoms including
thermal evaporation, electron beam evaporation, ion-driven sputtering, laser ablation, and
cathodic arc-based emission. Some of the approaches are based on a plasma discharge, while
in other cases the atoms composing the vapor are ionized either due to the release of the
film-forming species or they are ionized intentionally afterward. Here, a brief overview of the
various PVD techniques is given, while the emphasis is on sputtering, which is dominated by
magnetron sputtering, the most widely used technique for deposition of both metallic and
compound thin films. The advantages and drawbacks of the various techniques are discussed
and compared
Modelling ground pickup for microwave telescopes
Microwave telescopes require an ever-increasing control of experimental
systematics in their quest to measure the Cosmic Microwave Background (CMB) to
exquisite levels of precision. One important systematic for ground and
balloon-borne experiments is ground pickup, where beam sidelobes detect the
thermal emission of the much warmer ground while the main beam is scanning the
sky. This generates scan-synchronous noise in experiment timestreams, which is
difficult to filter out without also deleting some of the signal from the sky.
Therefore, efficient modelling of pickup can help guide the design of
experiments and of analysis pipelines. In this work, we present an extension to
the beamconv algorithm that enables us to generate time-ordered data (TOD) from
beam-convolved sky and ground maps simultaneously. We simulate ground pickup
for both a ground-based experiment and a telescope attached to a stratospheric
balloon. Ground templates for the balloon experiment are obtained by
re-projecting satellite maps of the Earth's microwave emission.Comment: 10 pages, 6 figures, paper 12190-165 for the "SPIE AT+I 2022 mm,
sub-mmm, and Far-Infrared Detectors and Instrumentation for Astronomy XI"
conferenc
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