Fabrication and Characterization of Nano-sized Magnetic Structures and Their Flux-pinning Effects on Superconducting Thin Films PDF Download
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Author: Han Gil Lee
Publisher:
ISBN:
Category :
Languages : en
Pages :
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This dissertation describes experimental studies of how a spatially alternating magnetic field can effectively pin the magnetic flux in a superconducting thin film (Pb 82 Bi18), thereby enhancing the superconductivity. The spatially alternating magnetic field was provided by a periodic array of nano-sized magnetic structures: 300 nm spacing triangular array of cobalt rods with 100 nm diameter and 300 nm height. The superconducting film deposited on top of the magnetic structures, or an embedded Ferromagnet- Superconductor Hybrids (FSH), showed enhanced critical current and critical magnetic field. The embedded FSH also showed the field matching effect, the field compensation effect, and hysteresis. This dissertation also explains how to fabricate and characterize magnetic nano- structures. Electron beam lithography and electroplating method were used to fabricate the magnetic nanostructures. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize the structures of the magnetic rods. Magnetic force microscopy (MFM) was used to study their magnetic properties.
Author: Han Gil Lee
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
This dissertation describes experimental studies of how a spatially alternating magnetic field can effectively pin the magnetic flux in a superconducting thin film (Pb 82 Bi18), thereby enhancing the superconductivity. The spatially alternating magnetic field was provided by a periodic array of nano-sized magnetic structures: 300 nm spacing triangular array of cobalt rods with 100 nm diameter and 300 nm height. The superconducting film deposited on top of the magnetic structures, or an embedded Ferromagnet- Superconductor Hybrids (FSH), showed enhanced critical current and critical magnetic field. The embedded FSH also showed the field matching effect, the field compensation effect, and hysteresis. This dissertation also explains how to fabricate and characterize magnetic nano- structures. Electron beam lithography and electroplating method were used to fabricate the magnetic nanostructures. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize the structures of the magnetic rods. Magnetic force microscopy (MFM) was used to study their magnetic properties.
Author: Wonbae Bang
Publisher:
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Category :
Languages : en
Pages :
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This research investigates the transport properties of ferromagnetic nanostructures made by nickel or cobalt on superconducting thin films. The superconducting thin films were covered by an insulating layer, and the periodic ferromagnetic nanostructures were fabricated on top of the insulating layer. On separate superconducting thin films, periodic ferromagnetic nanostructures were embedded into the thin films. The photolithography method was used to make contact pads for a four-probe measurement. In order to fabricate the magnetic nanostructures, an Electron Beam Lithography (EBL) system was utilized. The nanoscale patterns were filled with ferromagnetic materials by using a thermal evaporating method or an electroplating technique. The superconducting properties were measured at low temperature (2.0 K
Author: J.A.C. Bland
Publisher: Springer Science & Business Media
ISBN: 3540271635
Category : Technology & Engineering
Languages : en
Pages : 329
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Book Description
The ability to understand and control the unique properties of interfaces has created an entirely new field of magnetism which already has a profound impact in technology and is providing the basis for a revolution in electronics. The last decade has seen dramatic progress in the development of magnetic devices for information technology but also in the basic understanding of the physics of magnetic nanostructures. This volume describes thin film magnetic properties and methods for characterising thin film structure topics that underpin the present 'spintronics' revolution in which devices are based on combined magnetic materials and semiconductors. Volume IV deals with the fundamentals of spintronics: magnetoelectronic materials, spin injection and detection, micromagnetics and the development of magnetic random access memory based on GMR and tunnel junction devices. Together these books provide readers with a comprehensive account of an exciting and rapidly developing field. The treatment is designed to be accessible both to newcomers and to experts already working in this field who would like to get a better understanding of this very diversified area of research.
Author: Dino Fiorani
Publisher: Springer Science & Business Media
ISBN: 0387260188
Category : Science
Languages : en
Pages : 309
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Book Description
A collection of articles on different approaches to the investigation of surface effects on nanosized magnetic materials, with special emphasis on magnetic nanoparticles. The book provides an overview of progress in the field through recent results.
Author: Vincent Dusastre
Publisher: World Scientific
ISBN: 9814464333
Category : Science
Languages : en
Pages : 360
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Book Description
The search for cleaner, cheaper, smaller and more efficient energy technologies has to a large extent been motivated by the development of new materials. The aim of this collection of articles is therefore to focus on what materials-based solutions can offer and show how the rational design and improvement of their physical and chemical properties can lead to energy-production alternatives that have the potential to compete with existing technologies. In terms of alternative means to generate electricity that utilize renewable energy sources, the most dramatic breakthroughs for both mobile (i.e., transportation) and stationary applications are taking place in the fields of solar and fuel cells. And from an energy-storage perspective, exciting developments can be seen emerging from the fields of rechargeable batteries and hydrogen storage.
Author: Brandon N. Davis
Publisher:
ISBN: 9781085776684
Category : Magnetic materials
Languages : en
Pages : 77
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Book Description
With the continuous advancement of nanoscale-based data storage and memory technologies, a significant reduction in the dimensions of various materials and devices lead to an array of advancement-hindering phenomenon. The roadblock for these technologies is to find nanomaterials that can support the operation and progression with reducing scales. The focus of the presented research is to create new thin film compositions that take advantage of already optimized conventional materials. We explore layering different thin films in a way that uses the strength of each material while minimizes their weaknesses. These multilayer thin films are tailor-made to the specific functionality of a device or technology. In this work, design, fabrication, and characterization solutions relating to optical-based and magnetic-based futuristic nanotechnologies are explored.
Author: Laura Cattaneo
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Wenming Ju
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Nano-scale magnetic patterned structures and thin films have attracted attention over the past few years due to their unique magnetization distribution and promising application in nonvolatile data storage, magnetic field sensors and spintronic devices. Magnetization states and their switching processes are fundamental investigation subjects of such magnetic systems. This dissertation discusses experimental work and theoretical analysis on investigating the magnetization of these nano-scale magnetic structures and how we can characterize and manipulate the magnetization in order to realize industrial application. The efforts done in this dissertation can be grouped into three topics: First, we focus on whether we can reverse the vortex circulation of the ferromagnetic nanodisk without breaking its symmetry so as to control and manipulate the chirality of the nanodisk. The vortex state of ferromagnetic nanodisk is characterized with and without in-plane magnetic field. The vortex circulation switching is achieved by applying a local circular magnetic field which is created by passing current through an AFM tip that is in contact with the nanodisk. The experimental results indicate the success of the reversal when a dielectric breakdown happens during the current application and the breakdown voltage is above a threshold value. This implies that the concentration of the current in the center of the disk leads to a stronger magnetic field and lower switching current. The analysis is supported by the results of micromagnetic simulations conducted in this work. Second, a magnetometer based on Magneto-optical Kerr effect is constructed. It is then used to record the hysteresis loop of permalloy and cobalt amorphous thin films. At the same time the affect of skew angles in Magneto-optical Kerr effect is also investigated so that the skew angle that leads to highest Kerr signal can be determined. The setup lays a foundation which enables us to investigate the magnetic properties of various magnetic structures and develop other techniques for related study, so some future work related to interlayer exchange coupling of trilayer structure and Magneto-optical Kerr imaging are proposed. Last, the thermal diffusivity measurement of Co/Cu multilayer by laser flash technique is conducted with and without in-plane magnetic field. The experimental result shows that the application of magnetic field does not lead to a significant change in the thermal diffusivity of this structure. This phenomenon is interesting as it is different from the behavior of the electrical conductivity of this structure when magnetic field is applied (giant magnetoresistance effect). Some exploratory discussion is presented in the end.
Author: Chang-Peng Li
Publisher:
ISBN:
Category :
Languages : en
Pages : 123
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Nanostructured magnets have attracted great interest recently due to their new magnetic properties, which are completely different from those in the bulk, and their potential application in device miniaturization approaching the Tbit/in2 recording density. In this thesis, we have fabricated sub-100 nm magnetic dots covering over 1 cm2 area by electron-beam evaporation using self-assembled nanopores in anodized alumina as a shadow mask. Due to the large pattern coverage, and high degree of uniformity in both dot size and periodicity, magnetic measurements of such a dot array can be used to investigate the magnetism of a single dot of the average size. For Fe dots with a thickness of 20 nm, we find a transition from a single domain to a vortex state as the dot diameter is increased up to 60 nm. This single domain to vortex state transition has also been studied by the first order reversal curve method, which quantifies the magnetic phase fractions and distributions of vortex nucleation and annihilation fields. A magnetic vortex core size of 16±3 nm, which is close to or even smaller than the magnetic force microscopy (MFM) resolution, is measured by polarized neutron reflectivity measurements and verified by micromagnetic simulations. In addition to applications in magnetic memory systems and ultrasmall magnetic field sensors, magnetic nanostructures can also be used as the artificial pinning centers for superconducting vortices. We have observed asymmetric superconducting flux pinning effects with first matching fields above 2 kOe. Most importantly, we find that the properties of a magnetic vortex can be imprinted into transport properties of adjacent Al superconducting thin films, with dots' magnetic reversal events imprinted and magnified in the superconducting behavior. Chemical sensing and biosensing in porous alumina films, which exhibit more easily controlled pore sizes and higher chemical stability as compared to other porous materials, is studied using optical interferometry. The measured vapor capillary condensation and adsorption-desorption hysteresis is in qualitative agreement with theoretical models and a variety of simulations.
Author: Yue Zhao
Publisher:
ISBN:
Category : Magnesium compounds
Languages : en
Pages : 394
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