Lecture Notes in Physics

Lecture Notes in Physics Volume 969 Founding Editors Wolf Beiglböck, Heidelberg, Germany Jürgen Ehlers, Potsdam, Germany Klaus Hepp, Zürich, Switzerland Hans-Arwed Weidenmüller, Heidelberg, Germany Series Editors Matthias Bartelmann, Heidelberg, Germany Roberta Citro, Salerno, Italy Peter Hänggi, Augsburg, Germany Morten Hjorth-Jensen, Oslo, Norway Maciej Lewenstein, Barcelona, Spain Angel Rubio, Hamburg, Germany Manfred Salmhofer, Heidelberg, Germany Wolfgang Schleich, Ulm, Germany Stefan Theisen, Potsdam, Germany James D. Wells, Ann Arbor, MI, USA Gary P. Zank, Huntsville, AL, USA The Lecture Notes in Physics The series Lecture Notes in Physics (LNP), founded in 1969, reports new developments in physics research and teaching - quickly and informally, but with a high quality and the explicit aim to summarize and communicate current knowledge in an accessible way. Books published in this series are conceived as bridging material between advanced graduate textbooks and the forefront of research and to serve three purposes: • to be a compact and modern up-to-date source of reference on a well-defined topic. • to serve as an accessible introduction to the field to postgraduate students and nonspecialist researchers from related areas. • to be a source of advanced teaching material for specialized seminars, courses and schools. Both monographs and multi-author volumes will be considered for publication. Edited volumes should however consist of a very limited number of contributions only. Proceedings will not be considered for LNP. Volumes published in LNP are disseminated both in print and in electronic formats, the electronic archive being available at springerlink.com. The series content is indexed, abstracted and referenced by many abstracting and information services, bibliographic networks, subscription agencies, library networks, and consortia. Proposals should be sent to a member of the Editorial Board, or directly to the managing editor at Springer: Dr Lisa Scalone Springer Nature Physics Editorial Department Tiergartenstrasse 17 69121 Heidelberg, Germany [email protected] More information about this series at http://www.springer.com/series/5304 Sergio M. Rezende Fundamentals of Magnonics Sergio M. Rezende Departamento de Fisica Universidade Federal de Pernambuco Recife, Brazil ISSN 0075-8450 ISSN 1616-6361 (electronic) Lecture Notes in Physics ISBN 978-3-030-41316-3 ISBN 978-3-030-41317-0 (eBook) https://doi.org/10.1007/978-3-030-41317-0 # Springer Nature Switzerland AG 2020 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG. The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland To Adélia Preface Magnetism and magnetic materials constitute one of the oldest fields of science and technology that keeps renewing itself with new discoveries and unique technological applications. Centuries before the time of Christ, ancient civilizations studied the wondrous properties of magnetite, the famed loadstone, and used it for orientation in the Earth’s magnetic field. The magnetic compass became an essential instrument of navigation for the Chinese in ancient times and for the Europeans in the Late Middle Ages. This application motivated one of the oldest books in experimental physics, De Magnete, written by William Gilbert and published in 1600. After the discoveries of the fundamental laws of electromagnetism in the nineteenth century by Ampére, Oersted, Faraday, and Henry, magnetic materials became essential for the fabrication of generators, motors, and transformers, building blocks of electricity that revolutionized the costumes of humanity. Then, in the twentieth century, they made possible the invention of loudspeakers, phones, relays, and other magnetic devices essential for telegraphy and telephony, as well as the development of magnetic recording for audio, video, and digital information. With the understanding of the atomic origin of magnetism of matter, made possible by the formulation of quantum mechanics in the beginning of the twentieth century, new magnetic phenomena were proposed theoretically or discovered experimentally, and new applications were developed. In 1930, Felix Bloch showed that the low-lying excitations of the spin system consisted of nonlocalized, collective spin deviations, which he named spin waves, whose quanta are called magnons. Few decades later, spin waves were observed experimentally and became the subject of intense research. Phenomena involving the k ¼ 0 magnon, or ferromagnetic reso- nance, laid the groundwork for novel applications in microwave ferrite devices used in telecommunications, in radar systems, and in a variety of industrial equipment. Despite this long history of scientific activity and technological applications, recently Professor Chia-Ling Chien of the University of Baltimore stated that in the last 30 years, activity in magnetism is facing its Golden Age. The recent vigorous impulse to magnetism was provided by spin-based phenomena that occur in nanoscale magnetic structures, such as the giant magnetoresistance (GMR) discovered in 1989 by Albert Fert and Peter Grünberg, Physics Nobel Prize winners in 2007. The discovery of GMR and other spin-dependent phenomena led to new sensing devices that boosted the capacity of storage media and made possible vii viii Preface new storage devices such as the magnetic random-access memory. These and other developments led to the new field of spintronics, devoted to the investigation of basic phenomena and their application in devices for transport, storage, and processing of information, in which the main physical entity is the electron spin. The subfield of spintronics in which the phenomena are based on the properties of magnons is called magnonics, or magnon spintronics, which is the subject of this book. The unique properties of magnons in magnetic materials with very low damping, such as yttrium iron garnet (YIG), make them suitable for use as information carriers and logic processing without the need of electric current, overcoming an important fundamental limitation of conventional electronics: a power consumption which scales linearly with increasing number of individual processing elements.1,2 This book is intended to serve as a text for beginning engineering and physics graduate students in the areas of magnetism and spintronics. The level of presenta- tion assumes only basic knowledge of the origin of magnetism, electromagnetism, and quantum mechanics. The book utilizes relatively simple mathematical derivations, aimed mainly at explaining the physical concepts involved in the phenomena studied and for the understanding of the experiments presented. We use in the book both SI and CGS units, because they are equally employed in research articles. Key topics include the basic phenomena of ferromagnetic reso- nance in bulk materials and in thin films, semi-classical theory of spin waves, quantum theory of spin waves and magnons, magnons in antiferromagnets, parametric excitation of magnons, magnon nonlinear dynamics and chaotic phenomena, Bose–Einstein condensation of magnons, and the very recent field of magnon spintronics. This breath of topics is not covered in any other single book. Also, no other textbook on magnetism has the material presented in the last three chapters. I would like to thank many collaborators with whom I worked in several magnonic phenomena presented in the book. In particular, I thank Frederick R. Morgenthaler who introduced me to spin wave phenomena over 50 years ago, during my Ph.D. program at MIT. I am also grateful to Nicim Zagury, Robert M. White, Vincent Jaccarino, Carlos A. dos Santos, Wido R. Schreiner, Stuart S. P. Parkin, and Doug L. Mills, with whom I had profitable collaborations for many years. I also thank my colleagues, students, and post-docs at UFPE, my coauthors in papers on magnonics and other fields, Cid B. de Araújo, Ivon P. Fittipaldi, Mauricio D. Coutinho-Filho, José Rios Leite, Jairo R. L. de Almeida, Sandra S. Vianna, Fernando L. A. Machado, Erivaldo Montarroyos, J. Marcílio Ferreira, Eduardo Fontana, Flávio M. de Aguiar, Osiel A. Bonfim, Antonio 1Serga, A. A., Chumak, A. V., Hillebrands, B.: YIG Magnonics. J. Phys. D Appl. Phys. 43, 264002 (2010). 2Chumak, A. V., Vasyuchka, V. I., Serga, A. A.,

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