Hexagonal Ferrite Fibres and Nanofibres

2015 ◽  
Vol 241 ◽  
pp. 1-68 ◽  
Author(s):  
Robert C. Pullar
Keyword(s):  
Data Storage ◽  
Easy Axis ◽  
Permanent Magnets ◽  
Fibre Alignment ◽  
Storage Media ◽  
Cobalt Nickel ◽  
Electrical Devices ◽  
Recent Developments ◽  
The Common ◽  
Soft Ferrites

Hexagonal ferrites, or hexaferrites, are hugely important materials commercially and technologically, with common applications as permanent magnets, magnetic recording and data storage media, components in electrical devices operating at wireless frequencies, and as GHz electromagnetic wave absorbers for EMC, RAM and stealth technologies. Hexaferrites are all ferrimagnetic materials, and their magnetic properties are intrinsically linked to their crystalline structures, all having a strong magnetocrystalline anisotropy; that is the induced magnetisation has a preferred orientation within the crystal structure. They can be divided into two main groups: those with an easy axis of magnetisation (known as uniaxial), the hard hexaferrites, and those with an easy plane (or cone) of magnetisation (known as ferroxplana or hexaplana), soft ferrites. The common hexaferrite members are:M-type ferrites, such as BaFe12O19and SrFe12O19Z-type ferrites (Ba3Me2Fe24O41)Y-type ferrites (Ba2Me2Fe12O22)W-type ferrites (BaMe2Fe16O27)X-type ferrites (Ba2Me2Fe28O46)U-type ferrites (Ba4Me2Fe36O60)where Me = a small 2+ion such as cobalt, nickel or zinc, and Ba can be fully substituted by Sr. Generally, the M ferrites are hard, the Y, Z and U ferrites are soft, and the W and X ferrites can very between these two extremes, but all have large magnetisation (M) values.There is currently increasing interest in composite materials containing hexaferrite fibres. It had been predicted that properties such as thermal and electrical conductivity, and magnetic, electrical and optical behaviour will be enhanced in material in fibrous form. This is because a continuous fine fibre can be considered as effectively one-dimensional, and it does not behave as a homogeneously distributed solid. Although the intrinsic magnetisation of the material is unaffected, the effective magnetisation of an aligned fibre sample should be greater when a field is applied parallel with fibre alignment compared to when applied perpendicularly to fibre alignment. This feature was first demonstrated by the author for aligned hexaferrite fibres in 2006. This chapter will deal with progress in the manufacture and properties of hexaferrite fibres, from the first syntheses of BaM, SrM,Co2Y,Co2Z, Co2W, Co2X and Co2U micron-scale fibres by the author 12-15 years ago, to recent developments in M ferrite hollow fibres and nanofibres, and hexaferrite-coated CNTs (carbon nanotubes).The relative properties of all reported hexaferrite fibres are compared and summarised at the end of this chapter.

scholarly journals Hexagonal Ferrites, Synthesis, Properties and Their Applications

2021 ◽  
pp. 336-370
Author(s):  
P. Dhiman
Keyword(s):  
Magnetic Materials ◽  
Data Storage ◽  
Magnetic Recording ◽  
Permanent Magnets ◽  
Wide Area ◽  
Hexagonal Ferrites ◽  
Intrinsic Structure ◽  
High Frequencies ◽  
Electrical Devices ◽  
Synthesis Properties

We intend to report on possible fabrication routes for all types of hexagonal ferrites which are known for their wide area of use and applications. Hexagonal ferrites have now become an intense topic of research as they are the part of most of magnetic recording and data storage applications globally. Hexagonal or popularly known as ‘Heaxa-ferrites’ are known for their utilization in permanent magnets and their utilization in electrical devices being operated at high frequencies especially at GHz frequencies. We have presented in this chapter all main six types of hexagonal ferrites i.e. M Type, Z-Type, Y-type, W-type, X-Type and U-type hexa-ferrites. Hexaferrites belong to ferromagnetic class of magnetic materials and their properties are purely dependent on intrinsic structure of ferrites. In this chapter, we aim to discuss more on M-type of hexa-ferrites, their properties and their applications. Also, recent advances on M-type ferrites are also a part of this chapter.

Theory and Method and the Stakes of a Fragmented Discipline: Or, What Economics Taught Me About the Study of Religion

2020 ◽  
Author(s):  
Thomas A Lewis
Keyword(s):  
Religious Studies ◽  
The Public ◽  
Global Pandemic ◽  
Recent Developments ◽  
The Common ◽  
The Impact ◽  
Academic Study

Abstract As a discipline, the academic study of religion is strikingly fragmented, with little engagement or shared criteria of excellence across subfields. Although important recent developments have expanded the traditions and peoples studied as well as the methods used, the current extent of fragmentation limits the impact of this diversification and pluralization. At a moment when the global pandemic is catalyzing profound pressures on our universities and disciplines, this fragmentation makes it difficult to articulate to the public, to non-religious studies colleagues, and to students why the study of religion matters. We therefore too often fall back on platitudes. I argue for a revitalized methods and theories conversation that connects us even as it bears our arguments and disagreements about what we do and how. Courses in methods and theories in the study of religion represent the most viable basis we have for bringing the academic study of religion into the common conversation or argument that constitutes a discipline without sacrificing our pluralism.

scholarly journals Promiscuous molecules for smarter file operations in DNA-based data storage

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kyle J. Tomek ◽  
Kevin Volkel ◽  
Elaine W. Indermaur ◽  
James M. Tuck ◽  
Albert J. Keung
Keyword(s):  
Data Storage ◽  
Data Access ◽  
Molecular Architecture ◽  
Biomolecular Structure ◽  
Jpeg Images ◽  
Storage Media ◽  
Dna Storage ◽  
Dna Strands ◽  
Background Database ◽  
Organizational Features

AbstractDNA holds significant promise as a data storage medium due to its density, longevity, and resource and energy conservation. These advantages arise from the inherent biomolecular structure of DNA which differentiates it from conventional storage media. The unique molecular architecture of DNA storage also prompts important discussions on how data should be organized, accessed, and manipulated and what practical functionalities may be possible. Here we leverage thermodynamic tuning of biomolecular interactions to implement useful data access and organizational features. Specific sets of environmental conditions including distinct DNA concentrations and temperatures were screened for their ability to switchably access either all DNA strands encoding full image files from a GB-sized background database or subsets of those strands encoding low resolution, File Preview, versions. We demonstrate File Preview with four JPEG images and provide an argument for the substantial and practical economic benefit of this generalizable strategy to organize data.

Vacuum Coating Technology For Optical Data Storage Media

2006 ◽  
Vol 18 (S1) ◽  
pp. 38-44
Author(s):  
Bernhard Cord ◽  
Michael Mücke ◽  
Eggo Sichmann
Keyword(s):  
Data Storage ◽  
Optical Data Storage ◽  
Optical Data ◽  
Coating Technology ◽  
Storage Media

“Unity in Diversity” Reloaded: The European Court of Human Rights’ Turn to Subsidiarity and its Consequences

2021 ◽  
Vol 15 (1) ◽  
pp. 93-123
Author(s):  
Mikael Rask Madsen
Keyword(s):  
Human Rights ◽  
European Convention ◽  
Reform Process ◽  
Individual Member ◽  
Member States ◽  
European Court ◽  
Recent Developments ◽  
Unity In Diversity ◽  
The Common ◽  
Individual Justice

Abstract The European Convention of Human Rights system was originally created to sound the alarm if democracy was threatened in the member states. Yet, it eventually developed into a very different system with a focus on providing individual justice in an ever growing number of member states. This transformation has raised fundamental questions as to the level of difference and diversity allowed within the common European human rights space. Was the system to rest on minimum standards with room for domestic differences, or was it to create uniform standards? These questions have come up as increasingly contentious issues over the past years and have triggered a number of reforms seeking to introduce more subsidiarity in the system, striking a different balance between the European and national oversight of human rights. The article analyses this turn to subsidiarity by exploring whether the reform process has introduced new forms of difference and diversity within the common space of European human rights. Covering the period from 2000 to the end of 2019 and using a dataset of all judgments of the period, the article provides a structural analysis of developments in reference to the margin of appreciation which is the European Court of Human Rights’ long-standing tool for balancing the common standards, yet leaving space for individual member states to find local solutions to implementing those standards. It concludes that recent developments have contributed to a more federal-style construction of European human rights with more space for differences within the common general standards.

Transpermanent Magnetics Using Alternating Uniform Linear Stacks

2004 ◽  
Vol 127 (4) ◽  
pp. 679-687
Author(s):  
Larry Silverberg ◽  
Luis Duval
Keyword(s):  
Low Power ◽  
Permanent Magnets ◽  
Traditional Approach ◽  
Reducing Power ◽  
Ultra Low Power ◽  
Flow Rates ◽  
Recent Developments ◽  
Valve Control ◽  
Design And Testing ◽  
Laboratory Prototype

In this paper we apply recent developments in transpermanent magnetics to the problem of ultra-low-power valve control. Whereas the traditional approach to ultra-low-power valve control is based on latching mechanisms that turn off valves during inactive periods, in this paper we describe an approach that eliminates the need for latching mechanisms. Instead of latching mechanisms, the principles of transpermanent magnetics are employed to switch the states of permanent magnets; the use of permanent magnets instead of electromagnets eliminates power loads during inactive periods, thereby reducing power consumption to ultralow levels. The permanent magnets in a transpermanent magnet valve are configured in a stack. The relationships between the strength and number of permanent magnets in the stack and the stroke and resolution of the valve are developed. In this paper we show that the alternating uniform linear stack is well suited for digital process valves having a small number of states. Then in the paper we report on the design and testing of a laboratory prototype valve that uses an alternating uniform linear stack. The prototype valve had five states yielding a range of flow rates between 0 and 1.58m∕s with a resolution of 0.3m∕s. In this paper we find that transpermanent valves represent a promising valve technology for digital process valves.

scholarly journals Effect of oxidizing and reducing atmospheres on Ba(Ti0.90 Zr0.10)o3:2V ceramics as characterized by piezoresponse force microscopy

2011 ◽  
Vol 5 (3) ◽  
pp. 139-147 ◽  
Author(s):  
Francisco Moura ◽  
Alexandre Simões ◽  
Carla Riccardi ◽  
Maria Zaghete ◽  
Jose Varela ◽  
...  
Keyword(s):  
Data Storage ◽  
Photoelectron Spectroscopy ◽  
Ferroelectric Properties ◽  
Piezoresponse Force Microscopy ◽  
Nitrogen Atmosphere ◽  
Ambient Atmosphere ◽  
Practical Applications ◽  
Force Microscopy ◽  
Storage Media ◽  
Piezoelectric Force Microscopy

The effect of annealing atmospheres (Atamb, N2 and O2) on the electrical properties of Ba(Ti0.90Zr0.10 )O3:2V (BZT10:2V) ceramics obtained by the mixed oxide method was investigated. X-ray photoelectron spectroscopy (XPS) analysis indicates that oxygen vacancies present near Zr and Ti ions reduce ferroelectric properties, especially in samples treated in an ambient atmosphere (Atamb ). BZT10:2V ceramics sintered in a nitrogen atmosphere showed better dielectric behaviour at room temperature with a dielectric permittivity measured at a frequency of 10 kHz equal to 16800 with dielectric loss of 0.023. Piezoelectric force microscopy (PFM) images reveal improvement in the piezoelectric coefficient by sintering the sample under nitrogen atmosphere. Thus, BZT10:2V ceramics sintered under a nitrogen atmosphere can be useful for practical applications which include nonvolatile digital memories, spintronics and data-storage media.

Sign in / Sign up

Export Citation Format

Share Document