Angular Dependent Magnetization Dynamics of Kagome Artificial Spin Ice Incorporating Topological Defects

We report angular-dependent spin-wave spectroscopy on kagome artificial spin ice made of large arrays of interconnected Ni80Fe20 nanobars. Spectra taken in saturated and disordered states exhibit a series of resonances with characteristic in-plane angular dependencies. Micromagnetic simulations allow us to interpret characteristic resonances of a two-step magnetization reversal of the nanomagnets. The dynamic properties are consistent with topological defects that are provoked via a magnetic field applied at specific angles. Simulations that we performed on previously investigated kagome artificial spin ice consisting of isolated nanobars show characteristic discrepancies in the spin wave modes which we explain by the absence of vertices.Comment: 14 pages and 5 figure

Observation of vortex-nucleated magnetization reversal in individual ferromagnetic nanotubes

The reversal of a uniform axial magnetization in a ferromagnetic nanotube (FNT) has been predicted to nucleate and propagate through vortex domains forming at the ends. In dynamic cantilever magnetometry measurements of individual FNTs, we identify the entry of these vortices as a function of applied magnetic field and show that they mark the nucleation of magnetization reversal. We find that the entry field depends sensitively on the angle between the end surface of the FNT and the applied field. Micromagnetic simulations substantiate the experimental results and highlight the importance of the ends in determining the reversal process. The control over end vortex formation enabled by our findings is promising for the production of FNTs with tailored reversal properties.Comment: 20 pages, 13 figure

Impact of periodic intermediary flows on submarine melting of a Greenland glacier

Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 119 (2014): 7078–7098, doi:10.1002/2014JC009953.The submarine melting of a vertical glacier front, induced by an intermediary circulation forced by periodic density variations at the mouth of a fjord, is investigated using a nonhydrostatic ocean general circulation model and idealized laboratory experiments. The idealized configurations broadly match that of Sermilik Fjord, southeast Greenland, a largely two layers system characterized by strong seasonal variability of subglacial discharge. Consistent with observations, the numerical results suggest that the intermediary circulation is an effective mechanism for the advection of shelf anomalies inside the fjord. In the numerical simulations, the advection mechanism is a density intrusion with a velocity which is an order of magnitude larger than the velocities associated with a glacier-driven circulation. In summer, submarine melting is mostly influenced by the discharge of surface runoff at the base of the glacier and the intermediary circulation induces small changes in submarine melting. In winter, on the other hand, submarine melting depends only on the water properties and velocity distribution at the glacier front. Hence, the properties of the waters advected by the intermediary circulation to the glacier front are found to be the primary control of the submarine melting. When the density of the intrusion is intermediate between those found in the fjord's two layers, there is a significant reduction in submarine melting. On the other hand, when the density is close to that of the bottom layer, only a slight reduction in submarine melting is observed. The numerical results compare favorably to idealized laboratory experiments with a similar setup.Support to C. Cenedese and F. Straneo was given by the National Science Foundation project OCE-1130008. C. Cenedese received support also from the WHOI Arctic Research Initiative. R. Sciascia and P. Heimbach are supported in part by NSF project OCE-1129746. Additional funding for P. Heimbach comes through NASA's project NNH11ZDA001N-IDS A.28.2015-04-2

Imaging magnetic vortex configurations in ferromagnetic nanotubes

We image the remnant magnetization configurations of CoFeB and permalloy nanotubes (NTs) using x-ray magnetic circular dichroism photo-emission electron microscopy. The images provide direct evidence for flux-closure configurations, including a global vortex state, in which magnetization points circumferentially around the NT axis. Furthermore, micromagnetic simulations predict and measurements confirm that vortex states can be programmed as the equilibrium remnant magnetization configurations by reducing the NT aspect ratio.Comment: 14 pages, 4 figures, link to supplementary informatio

Разработка технологического процесса изготовления корпуса КС4372.212.11.001

РЕФЕРАТ Выпускная квалификационная работа содержит: 106 страниц текста, 27 таблиц, 32 источника литературы, 3 приложения, 12 листов графической части. Тема выпускной квалификационной работы «Разработка технологического процесса изготовления корпуса КС 4372.212.11.001». Ключевые слова: ТЕХНОЛОГИЧЕСКИЙ ПРОЦЕСС, ДЕТАЛЬ, ЗАГО-ТОВКА, РЕЖУЩИЙ ИНСТРУМЕНТ, ТЕХНОЛОГИЧЕСКОЕ ОБОРУДОВА-НИЕ, СЕБЕСТОИМОСТЬ ИЗГОТОВЛЕНИЯ, БАЗИРОВАНИЕ, ПРИПУСК. Годовая программа выпуска 1400 штук. В аналитической части приводится описание служебного назначения дета-ли, а также рассмотрен базовый технологический процесс с отработкой его на технологичность. В технологической части производится выбор заготовки и методов ее по-лучения, составление маршрута механической обработки в условиях серийного производства. В теоретичесZUSAMMENFASSUNG Finale qualifiziert Arbeit enthält 106 Seiten Text, 27 Tabellen, 32 Litera-turquellen, 3 Anwendungen, 12 Blatt Grafik Stunden-Minuten. Das Thema der letzten Qualifikations Arbeit "Entwicklung des technolo-gischen Prozesses der Herstellung des Körpers des KS 4372.212.11.001». Stichwort: Workflow, TEIL Zago-Reparatur, Schneidwerkzeuge, technische Ausrüstung-tion, Herstellungskosten, Geld stützen. Die jährliche Veröffentlichung des Programms in 1400 Stücke. Der analytische Teil ist der Service Zweck Beschreibung Teil-Do und einen grundlegenden Prozess betrachtet mit auf seine Verarbeitbarkeit zu arbeiten. In dem technischen Teil auswählt, das Werkstück und seine Methoden in Strahlung, um die Zusammensetzung der Bearbeitungsbahn in einer Serienproduk-tion. Im theoretischen Te

Imaging stray magnetic field of individual ferromagnetic nanotubes

We use a scanning nanometer-scale superconducting quantum interference device to map the stray magnetic field produced by individual ferromagnetic nanotubes (FNTs) as a function of applied magnetic field. The images are taken as each FNT is led through magnetic reversal and are compared with micromagnetic simulations, which correspond to specific magnetization configurations. In magnetic fields applied perpendicular to the FNT long axis, their magnetization appears to reverse through vortex states, i.e.\ configurations with vortex end domains or -- in the case of a sufficiently short FNT -- with a single global vortex. Geometrical imperfections in the samples and the resulting distortion of idealized mangetization configurations influence the measured stray-field patterns.Comment: 14 pages, 4 figure