5 research outputs found
Multistep Bloch-line-mediated Walker breakdown in ferromagnetic strips
A well-known feature of magnetic field driven dynamics of domain walls in
ferromagnets is the existence of a threshold driving force at which the
internal magnetization of the domain wall starts to precess -- a phenomenon
known as the Walker breakdown -- resulting in an abrupt drop of the domain wall
propagation velocity. Here, we report on micromagnetic simulations of magnetic
field driven domain wall dynamics in thin ferromagnetic strips with
perpendicular magnetic anisotropy which demonstrate that in wide enough strips
Walker breakdown is a multistep process: It consists of several distinct
velocity drops separated by short linear parts of the velocity vs field curve.
These features originate from the repeated nucleation, propagation and
annihilation of an increasing number of Bloch lines within the domain wall as
the driving field magnitude is increased. This mechanism arises due to
magnetostatic effects breaking the symmetry between the two ends of the domain
wall.Comment: 6 pages, 4 figures, to appear in Phys. Rev.
Nanofiber-based high-Q microresonator for cryogenic applications
We demonstrate a cryo-compatible, fully fiber-integrated, alignment-free
optical microresonator. The compatibility with low temperatures expands its
possible applications to the wide field of solid-state quantum optics, where a
cryogenic environment is often a requirement. At a temperature of 4.6 K we
obtain a quality factor of . In conjunction
with the small mode volume provided by the nanofiber, this cavity can be either
used in the coherent dynamics or the fast cavity regime, where it can provide a
Purcell factor of up to 15. Our resonator is therefore suitable for
significantly enhancing the coupling between light and a large variety of
different quantum emitters and due to its proven performance over a wide
temperature range, also lends itself for the implementation of quantum hybrid
systems.Comment: 9 pages, 3 figure
Granular Hall sensors for scanning probe microscopy
Scanning Hall probe microscopy is attractive for minimally invasive characterization of magnetic thin films and nanostructures by measurement of the emanating magnetic stray field. Established sensor probes operating at room temperature employ highly miniaturized spin-valve elements or semimetals, such as Bi. As the sensor layer structures are fabricated by patterning of planar thin films, their adaption to custom-made sensor probe geometries is highly challenging or impossible. Here we show how nanogranular ferromagnetic Hall devices fabricated by the direct-write method of focused electron beam induced deposition (FEBID) can be tailor-made for any given probe geometry. Furthermore, we demonstrate how the magnetic stray field sensitivity can be optimized in situ directly after direct-write nanofabrication of the sensor element. First proof-of-principle results on the use of this novel scanning Hall sensor are shown
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Nanofiber-based high-Q microresonator for cryogenic applications
We demonstrate a cryo-compatible, fully fiber-integrated, alignment-free optical microresonator. The compatibility with low temperatures expands its possible applications to the wide field of solid-state quantum optics, where a cryogenic environment is often a requirement. At a temperature of 4.6 K we obtain a quality factor of (9.9 ± 0.7) × 106. In conjunction with the small mode volume provided by the nanofiber, this cavity can be either used in the coherent dynamics or the fast cavity regime, where it can provide a Purcell factor of up to 15. Our resonator is therefore suitable for significantly enhancing the coupling between light and a large variety of different quantum emitters and due to its proven performance over a wide temperature range, also lends itself for the implementation of quantum hybrid systems. © 2020 OSA - The Optical Society. All rights reserved
Focused electron beam-based 3D nanoprinting for scanning probe microscopy: a review
Scanning probe microscopy (SPM) has become an essential surface characterization technique in research and development. By concept, SPM performance crucially depends on the quality of the nano-probe element, in particular, the apex radius. Now, with the development of advanced SPM modes beyond morphology mapping, new challenges have emerged regarding the design, morphology, function, and reliability of nano-probes. To tackle these challenges, versatile fabrication methods for precise nano-fabrication are needed. Aside from well-established technologies for SPM nano-probe fabrication, focused electron beam-induced deposition (FEBID) has become increasingly relevant in recent years, with the demonstration of controlled 3D nanoscale deposition and tailored deposit chemistry. Moreover, FEBID is compatible with practically any given surface morphology. In this review article, we introduce the technology, with a focus on the most relevant demands (shapes, feature size, materials and functionalities, substrate demands, and scalability), discuss the opportunities and challenges, and rationalize how those can be useful for advanced SPM applications. As will be shown, FEBID is an ideal tool for fabrication/modification and rapid prototyping of SPM-tipswith the potential to scale up industrially relevant manufacturing