Magnetic Neutron Diffraction

The inter action between the magnetic field generated by the neutron and the magnetic moment of atoms containing unpaired electrons was experimentally demonstrated for the first time about twenty years ago. The basic theory describing such an in teraction had already been developed and the first nuclear reactors with large available thermal neutron fluxes had recently been con structed. The power of the magnetic neutron interaction for in vestigating the structure of magnetic materials was immediately recognized and put to use where possible. Neutron diffraction, however, was practicable only in countries with nuclear reactors. The earliest neutron determinations of magnetic ordering were hence primarily carried out at Oak Ridge and Brookhaven in the US, at Chalk River in Canada and at Harwell in England. Diffraction patterns from polycrystalline ferromagnets and antiferromagnets are interpretable if produced by simple spin arrays. More complex magnetic scattering patterns could often be unravelled, in terms of a three-dimensional array of atomic moments, if the specimen studied is a single crystal. The devel opment of sophisticated cryogenic equipment, with independently alignable magnetic fields, opened the way to greater complexity in the magnetic structures that could be successfully determined, as did also the introduction of polarized neutron beams. By the end of the 'sixties, many countries were contributing significantly to neutron diffraction studies of a wide variety of magnetic materials.

Detennination of the magnetic structure of magnetic materials is a fundamental problem that can be solved by magnetic neutron diffraction techniques. By magnetic structures we refer to the mutual alignment of the magnetic moments of the atoms in a crystal and their overall alignment relative to the crystallographic axes. Some indirect, tentative data on the magnetic structure of magnetic materials can be obtained from research on their magnetic, mechanical, thermal, and other properties. But only neutron diffraction is a unique direct method of detennining the magnetic structure of a crystal. The magnetic structure of more than one thousand crystals with magnetic order has been studied during 30 years of neutron diffraction research made on reactors in a large number of laboratories in the world. The results of this research work are extensively described in the handbook Magnetic Structures Determined by Neutron Diffraction [176]; in the present book, we will often refer to this handbook. The first extensive theoretical generalization of the principles of magnetic neutron diffraction and the results of research on magnetic structures appeared in the book by Yu. A. Izyumov and R. P. Ozerov Magnetic Neutron Diffraction [24, 134].

The inter action between the magnetic field generated by the neutron and the magnetic moment of atoms containing unpaired electrons was experimentally demonstrated for the first time about twenty years ago. The basic theory describing such an in teraction had already been developed and the first nuclear reactors with large available thermal neutron fluxes had recently been con structed. The power of the magnetic neutron interaction for in vestigating the structure of magnetic materials was immediately recognized and put to use where possible. Neutron diffraction, however, was practicable only in countries with nuclear reactors. The earliest neutron determinations of magnetic ordering were hence primarily carried out at Oak Ridge and Brookhaven in the US, at Chalk River in Canada and at Harwell in England. Diffraction patterns from polycrystalline ferromagnets and antiferromagnets are interpretable if produced by simple spin arrays. More complex magnetic scattering patterns could often be unravelled, in terms of a three-dimensional array of atomic moments, if the specimen studied is a single crystal. The devel opment of sophisticated cryogenic equipment, with independently alignable magnetic fields, opened the way to greater complexity in the magnetic structures that could be successfully determined, as did also the introduction of polarized neutron beams. By the end of the 'sixties, many countries were contributing significantly to neutron diffraction studies of a wide variety of magnetic materials.

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.

The proceedings provide a topical survey of the static and dynamical magnetic properties of condensed matter studied by neutron scattering which has been the key technique in this field for a long time. The static aspects deal with the determination of long-range ordered spin structures and magnetization densities. The dynamic aspects concentrate on the determination of magnetic excitations such as spin waves and crystal-field transitions. The use of polarized-neutron techniques is particularly emphasized. All these topics are thoroughly introduced, methodically discussed, and highlighted with recent experimental results obtained for a vast variety of magnetic materials (e.g., strongly correlated electron systems, multilayers, nanocrystals, molecular complexes, etc.) by acknowledged experts. Other experimental methods (x-ray scattering, muon spin rotation) in the study of magnetism are compared to neutron scattering.

Neutron Scattering - Magnetic and Quantum Phenomena provides detailed coverage of the application of neutron scattering in condensed matter research. The book's primary aim is to enable researchers in a particular area to identify the aspects of their work where neutron scattering techniques might contribute, conceive the important experiments to be done, assess what is required to carry them out, write a successful proposal for one of the major user facilities, and perform the experiments under the guidance of the appropriate instrument scientist. An earlier series edited by Kurt Sköld and David L. Price, and published in the 1980s by Academic Press as three volumes in the series Methods of Experimental Physics, was very successful and remained the standard reference in the field for several years. This present work has similar goals, taking into account the advances in experimental techniques over the past quarter-century, for example, neutron reflectivity and spin-echo spectroscopy, and techniques for probing the dynamics of complex materials of technological relevance. This volume complements Price and Fernandez-Alonso (Eds.), Neutron Scattering - Fundamentals published in November 2013. Covers the application of neutron scattering techniques in the study of quantum and magnetic phenomena, including superconductivity, multiferroics, and nanomagnetism Presents up-to-date reviews of recent results, aimed at enabling the reader to identify new opportunities and plan neutron scattering experiments in their own field Provides a good balance between theory and experimental techniques Provides a complement to Price and Fernandez-Alonso (Eds.), Neutron Scattering - Fundamentals published in November 2013

X-Ray and Neutron Diffraction describes the developments of the X-ray and the various research done in neutron diffraction. Part I of the book concerns the principles and applications of the X-ray and neutrons through their origins from classical crystallography. The book explains the use of diffraction methods to show the highly regular arrangement of atoms that forms a continuous pattern in three-dimensional space. The text evaluates the limitations and benefits of using the different types of radiation sources, whether these are X-rays, neutrons, or electrons. Part II is a collection of reprints discussing the development of techniques that includes a modification of the Bragg method, which is a method of X-ray crystal analysis. One paper presents an improved numerical method of two-dimensional Fourier synthesis for crystals. This method uses a greatly reduced process of arrangement of sets of figures found in the two-dimensional Fourier series. The book also notes the theoretical considerations and the practical details, and then addresses precautions against possible inclusions of errors in this method. The text deals as well with the magnetic scattering of neutrons, and one paper presents a simple method of gathering information about the magnetic moment of the neutron besides the traditional Stern-Gerlach method. Nuclear scientists and physicists, atomic researchers, and nuclear engineers will greatly appreciate the book.