Neutrons as Magnetic Probes PDF Download

Author: Robert Nathans
Publisher:
ISBN:
Category : Magnetism
Languages : en
Pages : 24

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Andreas Michels
Publisher: Oxford University Press
ISBN: 0198855176
Category : Science
Languages : en
Pages : 374

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Book Description
Magnetic Small-Angle Neutron Scattering provides the first extensive treatment of magnetic small-angle neutron scattering (SANS). The theoretical background required to compute magnetic SANS cross sections and correlation functions related to long-wavelength magnetization structures is laidout. The concepts are scrutinized based on the discussion of experimental neutron data. Regarding prior background knowledge, some familiarity with the basic magnetic interactions and phenomena as well as scattering theory is desired.Besides exposing the different origins of magnetic SANS, and furnishing the basics of the magnetic SANS technique in early chapters, a large part of the book is devoted to a comprehensive treatment of the continuum theory of micromagnetics, as it is relevant for the study of the elastic magneticSANS cross section. Analytical expressions for the magnetization Fourier components allow to highlight the essential features of magnetic SANS and to analyze experimental data both in reciprocal, as well as in real space. Later chapters provide an overview on the magnetic SANS of nanoparticles andso-called complex systems (e.g., ferrofluids, magnetic steels, spin glasses and amorphous magnets). It is this subfield where major progress is expected to be made in the coming years, mainly via the increased usage of numerical micromagnetic simulations (Chapter 7), which is a very promisingapproach for the understanding of the magnetic SANS from systems exhibiting nanoscale spin inhomogeneity.

Author: Vikash Venkataramana
Publisher:
ISBN:
Category : Data disk drives
Languages : en
Pages : 0

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Author: Tapan Chatterji
Publisher: Elsevier
ISBN: 0080457053
Category : Science
Languages : en
Pages : 574

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Neutron Scattering from Magnetic Materials is a comprehensive account of the present state of the art in the use of the neutron scattering for the study of magnetic materials. The chapters have been written by well-known researchers who are at the forefront of this field and have contributed directly to the development of the techniques described. Neutron scattering probes magnetic phenomena directly. The generalized magnetic susceptibility, which can be expressed as a function of wave vector and energy, contains all the information there is to know about the statics and dynamics of a magnetic system and this quantity is directly related to the neutron scattering cross section. Polarized neutron scattering techniques raise the sophistication of measurements to even greater levels and gives additional information in many cases. The present book is largely devoted to the application of polarized neutron scattering to the study of magnetic materials. It will be of particular interest to graduate students and researchers who plan to investigate magnetic materials using neutron scattering. · Written by a group of scientist who have contributed directly in developing the techniques described.· A complete treatment of the polarized neutron scattering not available in literature.· Gives practical hits to solve magnetic structure and determine exchange interactions in magnetic solids.· Application of neutron scattering to the study of the novel electronic materials.

Author: Vikash Venkataramana
Publisher:
ISBN:
Category : Data disk drives
Languages : en
Pages : 410

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Magnetic recording media refers to the disc shaped thin film magnetic medium present inside the hard disk drive of a computer. Magnetic recording is an important function of the hard disk drive by which information such as text, pictures, audio and videos are stored. Information is broken down to a simple binary format and is stored as magnetised bits along the tracks of the disk forming the hard drive. Over the years advancements in research on the type of magnetic materials used has allowed increased data storage capacities by reducing magnetic bit sizes. It is with this advancement in magnetic data storage, that we have today's hard disk drive technology, which uses a perpendicular magnetic medium to store data. A perpendicular magnetic medium is a multi-layered magnetic thin film structure with the topmost layer comprising nanoscale magnetic grains of high perpendicular anisotropy. The topmost recording layer (RL) is mapped into individual bits of 80-100 nm2 area that consist of 5-10 nm diameter CoCrPt grains, embedded in an oxide matrix. A bit area is defined to ensure a significant number of stable grains allowing data to be stored in each bit as a '0' or a '1' depending on its switched magnetic state. The magnetic grains if sputtered below a threshold grain size tend to suffer from thermal fluctuation and instability due to super-paramagnetic effects, hence bringing limitations to grain size. As a result of this, research in recent years has been directed at introducing a softer magnetic exchange coupled composite (ECC) layer above the recording layer. This layer facilitates the delicate balance of switching smaller grains with strong magneto-crystalline anisotropy at lower magnetic fields, by exchange coupling with the CoCrPt grains in the recording layer. However this technique of increasing the efficiency in the perpendicular magnetic medium by introducing 'facilitating' layers is an area that is still being widely researched and understood. Although numerous surface and bulk analysis techniques exist to study magnetic and surface properties of these materials, there is limited information on the structural and magnetic properties of these materials at the nanoscale level. The reported work investigates the structural and magnetic properties of the magnetic grains and multi-layers in the perpendicular magnetic medium using polarised neutron scattering and reflectivity techniques. The work investigates the structural and magnetic properties of the CoCrPt grains, apart from understanding the CoCrPt magnetic grain switching. The work also investigates the magnetisation in the layers of the thin film perpendicular media structure using polarised neutron reflectivity (PNR). Using polarised small angle neutron scattering (PolSANS), it has been shown that ferromagnetic ordered core region of the CoCrPt grain in the recording layer is smaller than the physical CoCrPt granular structure. The magnetic switching behaviour of the CoCrPt grain at different magnetic fields is also analysed and the experimental PolSANS data is fitted with non-interacting size-dependent analytical grain switching models. This result provides significant evidence that the magnetic anisotropy increases with grain size, with larger magnetic grains having larger magnetic anisotropy. Polarised neutron scattering experiments are carried out with the magnetically softer exchange coupled composite (ECC) layer included in the thin film magnetic structure. The first experiments investigate if the ECC layer contributes to the nuclear and magnetic interference scattering term in the experimenting scattering data. The experiments clearly show that there is no contribution from the ECC layer in the nuclear and magnetic scattering interference term. The role of the ECC layer in the magnetic switching process is then investigated at different magnetic fields. The ECC layer was found to influence the size-dependent magnetic grain switching of the CoCrPt grains in the recording layer and a detailed investigation is presented in the reported work. Polarised neutron reflectivity (PNR) experiments have also been carried out with the ECC layer on the perpendicular magnetic media samples. These experiments investigate the composition and thickness of the thin film structure, while also providing information on the magnetic state of the thin films under the influence of an in-plane magnetic field. The in-plane magnetisation in the recording and ECC layer is determined at different in-plane magnetic fields. The magnetisation values determined for the ECC layer and the recording layer (RL) at different in-plane magnetic fields help better understand the differences in their magnetic properties.

Author: Albert Furrer
Publisher: World Scientific Publishing Company
ISBN:
Category : Condensed matter
Languages : en
Pages : 326

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Book Description
Neutron scattering has become a key technique for investigating the properties of materials on an atomic scale. The uniqueness of this method is based on the fact that the wavelength and energy of thermal neutrons ideally match interatomic distances and excitation energies in condensed matter, and thus neutron scattering is able to directly examine the static and dynamic properties of the material. In addition, neutrons carry a magnetic moment, which makes them a unique probe for detecting magnetic phenomena. In this important book, an introduction to the basic principles and instrumental aspects of neutron scattering is provided, and the most important phenomena and materials properties in condensed matter physics are described and exemplified by typical neutron scattering experiments, with emphasis on explaining how the relevant information can be extracted from the measurements.

Author: Ulrich Schollwöck
Publisher: Springer
ISBN: 3540400664
Category : Science
Languages : en
Pages : 488

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Book Description
Closing a gap in the literature, this volume is intended both as an introductory text at postgraduate level and as a modern, comprehensive reference for researchers in the field. Provides a full working description of the main fundamental tools in the theorists toolbox which have proven themselves on the field of quantum magnetism in recent years. Concludes by focusing on the most important cuurent materials form an experimental viewpoint, thus linking back to the initial theoretical concepts.

Author: J. M. Carpenter
Publisher: Cambridge University Press
ISBN: 0521857813
Category : Science
Languages : en
Pages : 539

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This book provides a comprehensive and up-to-date introduction to the fundamental theory and applications of slow-neutron scattering.

Author: Stephen W. Lovesey
Publisher: Springer Science & Business Media
ISBN: 1475798113
Category : Science
Languages : en
Pages : 332

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Book Description
The Advanced Research Workshop (ARW) on Condensed Matter Re search Using Neutrons, Today and Tomorrow was held in Abingdon, Oxfordshire for four days beginning 26 March 1984. The Workshop was sponsored by NATO and the Rutherford Appleton Laboratory. A total of 32 lecturers and participants attended. An objective of the Workshop was to review some dynamic proper ties of condensed matter that can be studied using neutron spectros copy. A second objective, no less important, was to identify new topics that might be investigated with advanced spallation neutron sources. The twelve lectures reproduced in this volume bear wit ness, largely by themselves, to the success of the Workshop in meet ing these objectives. The many discussions generated by lecturers and participants meant that, in the event, the objectives were in deed amply satisfied. I should like to thank all those who attended the Horkshop for their part in making it so beneficial and rewarding. I am most grateful to Reinhard Scherm, who acted as my advisor in the organisation of the Workshop. The efforts of Mrs. M. Sherwen and Miss J. Harren made light my burden of administrative duties. The preparation of the manuscript for publication was simplified by the assistance of Miss C. Monypenny.