Elsevier, 2001. 540 p.
The Handbook series Magnetic Materials is a continuation of the Handbook series Ferromagnetic Materials. When Peter Wohlfarth started the latter series, his original aim was to combine new developments in magnetism with the achievements of earlier compilations of monographs, producing a worthy successor to Bozorth's classical and monumental book Ferromagnetism. This is the main reason that Ferromagnetic Materials was initially chosen as title for the Handbook series, although the latter aimed at giving a more complete cross-section of magnetism than Bozorth's book.
In the last few decades magnetism has seen an enormous expansion into a variety of different areas of research, comprising the magnetism of several classes of novel materials that share with truly ferromagnetic materials only the presence of magnetic moments. For this reason the Editor and Publisher of this Handbook series have carefully reconsidered the title of the Handbook series and changed it into Magnetic Materials. It is with much pleasure that I can introduce to you now Volume 13 of this Handbook series.
The possibility of an exchange interaction between ferromagnetic films across a nonferromagnetic metallic interlayer has been considered already for a long time. However, it was only around 1986 that this interaction was clearly described and characterized in Fe/Cr structures and in rare earth based multilayers. An account of the latter type multilayers was already given chapter 1 of Volume
8. The interest in exchange coupled multilayers became strongly enhanced by the discovery of the giant magnetoresistance (GMR) effect. Also in this case there were already earlier reports of unusual magnetoresistive effects in layered structures, but it was only in 1988 that GMR effects were for the first time clearly observed and characterized in antiferromagnetically coupled Fe/Cr systems. The high potential of magnetoresistive effects for applications has generated an enormous amount of experimental and theoretical research activities, including the coupling phenomena. In chapter 1 of this Volume a general review of the experimental work on interlayer exchange coupling is presented along with a discussion of the current understanding of this field. A chapter on the GMR effect has already appeared in chapter 1 of Volume 12 of this series.
There exists quite an extensive amount of scientific efforts devoted to 4f and 5f systems, including experimental and theoretical, as well as basic and applied research. Chapter 2 aims at reviewing a part of these efforts from the viewpoint of microscopic theory, in succession of the chapter written by Brooks and Johansson in Volume
7. In chapter 2 of the present Volume, special attention is paid to the many new developments in the field, the presentation of the new developments being based on a broad tutorial discussion. An important ingredient of this chapter is the introduction of density functional theory (DFT). This is done on a level that will allow the reader to judge the most important details of the presented calculations. Here it is good to bear in mind that in the seventies, DFT calculations were the domain of a few specialists only. However, the number of applications of this rather universal computational tool has seen a rapid growth in later years. In spite of this fact, the number of scientists knowing the ins and outs of DFT theory is limited. As a consequence, the easily accessible DFT-based computer codes are frequently used without deeper knowledge of the underlying physics and the concomitant restrictions. One of the intentions of chapter 2 is to bring to the fore the darker areas of DFT theory applications.
The field of magneto-optics (MO) dates back to the discovery of the Faraday effect in 1845 and the Kerr effect in 1876. During many decades, the latter effect has been used extensively by solid state physicists to visualise surface and subsurface magnetic domains. At the end of the last century it was realised that MOKE could be employed to read-out suitably stored magnetic information, which soon developed into a leading technological application of MOKE. It was also realised that MO spectroscopy could be used to obtain experimental information on the band structure of magnetic solids. Progress in experimental techniques made it possible to perform measurement of MO spectra in a wide energy range and many of these results were reviewed in chapter 5 of Volume 4 and chapter 2 of Volume
5. Details of magneto-optical recording were presented in chapter 4 of Volume
6. The wealth of experimental results include magnetic materials based on 3d transition elements as well as materials composed of rare earth and actinide elements. Nowadays, MO spectra can be calculated from first-principles energy-band theory and it is even feasible to make ab initio predictions of MOKE spectra. A review of novel experimental results and first-principles energy-band calculations of MOKE spectra will be presented in chapter 3.
Despite our advanced understanding of a variety of different magnetic systems there is comparatively little known about a class of materials that is said to behave as geometrically frustrated. In such materials, frustration arises from the incompatibility between the local antiferromagnetic interaction and the global symmetry imposed by the crystal structure. These materials form a separate class in the sense that they share common macroscopic and microscopic properties. On the macroscopical level, they display properties characteristic of a thermodynamically large number of ground states. On the microscopical level, these materials have triangle-based magnetic lattices. They are underconstrained in the Maxwellian sense, and generally have isotropic spins. Owing to the strong commonalties among such materials, they fall into a category currently called geometrically frustrated magnets (GFMs). Such materials are described in chapter 4, where a review is presented with a more pedagogical focus that concentrates on two main goals. The first goal envisages providing an up-to-date source for information on specific magnetic materials, including the measurements which elucidate GFM behaviour. The second goal aims at drawing parallels to nonmagnetic condensed matter systems. Conventional co-operative phenomena,
such as long-range order and elementary excitations, have realisations in nonmagnetic situations. This applies also to the phenomena of geometrical frustration. In chapter 4 this topic is addressed by developing the basic principles underlying the magnetic phenomena.
Volume 13 of the Handbook on the Properties of Magnetic Materials, as the preceding volumes, has a dual purpose. As a textbook it is intended to be of assistance to those who wish to be introduced to a given topic in the field of magnetism without the need to read the vast amount of literature published. As a work of reference it is intended for scientists active in magnetism research. To this dual purpose, Volume 13 of the Handbook is composed of topical review articles written by leading authorities. In each of these articles an extensive description is given in graphical as well as in tabular form, much emphasis being placed on the discussion of the experimental material in the framework of physics, chemistry and material science.
The task to provide the readership with novel trends and achievements in magnetism would have been extremely difficult without the professionalism of the North Holland Physics Division of Elsevier Science B.V. , and I wish to thank Jonathan Clark and Wim Spaans for their great help and expertise.
Preface to Volume 13.
Contents.
Contents of Volumes 1-12.
List of Contributors.
Interlayer Exchange Coupling in Layered Magnetic Structures.
Density Functional Theory Applied to 4f and 5f Elements and Metallic Compounds.
Magneto-Optical Kerr Spectra.
Geometrical Frustration.
Author Index.
Subject Index.
Materials Index.
The Handbook series Magnetic Materials is a continuation of the Handbook series Ferromagnetic Materials. When Peter Wohlfarth started the latter series, his original aim was to combine new developments in magnetism with the achievements of earlier compilations of monographs, producing a worthy successor to Bozorth's classical and monumental book Ferromagnetism. This is the main reason that Ferromagnetic Materials was initially chosen as title for the Handbook series, although the latter aimed at giving a more complete cross-section of magnetism than Bozorth's book.
In the last few decades magnetism has seen an enormous expansion into a variety of different areas of research, comprising the magnetism of several classes of novel materials that share with truly ferromagnetic materials only the presence of magnetic moments. For this reason the Editor and Publisher of this Handbook series have carefully reconsidered the title of the Handbook series and changed it into Magnetic Materials. It is with much pleasure that I can introduce to you now Volume 13 of this Handbook series.
The possibility of an exchange interaction between ferromagnetic films across a nonferromagnetic metallic interlayer has been considered already for a long time. However, it was only around 1986 that this interaction was clearly described and characterized in Fe/Cr structures and in rare earth based multilayers. An account of the latter type multilayers was already given chapter 1 of Volume
8. The interest in exchange coupled multilayers became strongly enhanced by the discovery of the giant magnetoresistance (GMR) effect. Also in this case there were already earlier reports of unusual magnetoresistive effects in layered structures, but it was only in 1988 that GMR effects were for the first time clearly observed and characterized in antiferromagnetically coupled Fe/Cr systems. The high potential of magnetoresistive effects for applications has generated an enormous amount of experimental and theoretical research activities, including the coupling phenomena. In chapter 1 of this Volume a general review of the experimental work on interlayer exchange coupling is presented along with a discussion of the current understanding of this field. A chapter on the GMR effect has already appeared in chapter 1 of Volume 12 of this series.
There exists quite an extensive amount of scientific efforts devoted to 4f and 5f systems, including experimental and theoretical, as well as basic and applied research. Chapter 2 aims at reviewing a part of these efforts from the viewpoint of microscopic theory, in succession of the chapter written by Brooks and Johansson in Volume
7. In chapter 2 of the present Volume, special attention is paid to the many new developments in the field, the presentation of the new developments being based on a broad tutorial discussion. An important ingredient of this chapter is the introduction of density functional theory (DFT). This is done on a level that will allow the reader to judge the most important details of the presented calculations. Here it is good to bear in mind that in the seventies, DFT calculations were the domain of a few specialists only. However, the number of applications of this rather universal computational tool has seen a rapid growth in later years. In spite of this fact, the number of scientists knowing the ins and outs of DFT theory is limited. As a consequence, the easily accessible DFT-based computer codes are frequently used without deeper knowledge of the underlying physics and the concomitant restrictions. One of the intentions of chapter 2 is to bring to the fore the darker areas of DFT theory applications.
The field of magneto-optics (MO) dates back to the discovery of the Faraday effect in 1845 and the Kerr effect in 1876. During many decades, the latter effect has been used extensively by solid state physicists to visualise surface and subsurface magnetic domains. At the end of the last century it was realised that MOKE could be employed to read-out suitably stored magnetic information, which soon developed into a leading technological application of MOKE. It was also realised that MO spectroscopy could be used to obtain experimental information on the band structure of magnetic solids. Progress in experimental techniques made it possible to perform measurement of MO spectra in a wide energy range and many of these results were reviewed in chapter 5 of Volume 4 and chapter 2 of Volume
5. Details of magneto-optical recording were presented in chapter 4 of Volume
6. The wealth of experimental results include magnetic materials based on 3d transition elements as well as materials composed of rare earth and actinide elements. Nowadays, MO spectra can be calculated from first-principles energy-band theory and it is even feasible to make ab initio predictions of MOKE spectra. A review of novel experimental results and first-principles energy-band calculations of MOKE spectra will be presented in chapter 3.
Despite our advanced understanding of a variety of different magnetic systems there is comparatively little known about a class of materials that is said to behave as geometrically frustrated. In such materials, frustration arises from the incompatibility between the local antiferromagnetic interaction and the global symmetry imposed by the crystal structure. These materials form a separate class in the sense that they share common macroscopic and microscopic properties. On the macroscopical level, they display properties characteristic of a thermodynamically large number of ground states. On the microscopical level, these materials have triangle-based magnetic lattices. They are underconstrained in the Maxwellian sense, and generally have isotropic spins. Owing to the strong commonalties among such materials, they fall into a category currently called geometrically frustrated magnets (GFMs). Such materials are described in chapter 4, where a review is presented with a more pedagogical focus that concentrates on two main goals. The first goal envisages providing an up-to-date source for information on specific magnetic materials, including the measurements which elucidate GFM behaviour. The second goal aims at drawing parallels to nonmagnetic condensed matter systems. Conventional co-operative phenomena,
such as long-range order and elementary excitations, have realisations in nonmagnetic situations. This applies also to the phenomena of geometrical frustration. In chapter 4 this topic is addressed by developing the basic principles underlying the magnetic phenomena.
Volume 13 of the Handbook on the Properties of Magnetic Materials, as the preceding volumes, has a dual purpose. As a textbook it is intended to be of assistance to those who wish to be introduced to a given topic in the field of magnetism without the need to read the vast amount of literature published. As a work of reference it is intended for scientists active in magnetism research. To this dual purpose, Volume 13 of the Handbook is composed of topical review articles written by leading authorities. In each of these articles an extensive description is given in graphical as well as in tabular form, much emphasis being placed on the discussion of the experimental material in the framework of physics, chemistry and material science.
The task to provide the readership with novel trends and achievements in magnetism would have been extremely difficult without the professionalism of the North Holland Physics Division of Elsevier Science B.V. , and I wish to thank Jonathan Clark and Wim Spaans for their great help and expertise.
Preface to Volume 13.
Contents.
Contents of Volumes 1-12.
List of Contributors.
Interlayer Exchange Coupling in Layered Magnetic Structures.
Density Functional Theory Applied to 4f and 5f Elements and Metallic Compounds.
Magneto-Optical Kerr Spectra.
Geometrical Frustration.
Author Index.
Subject Index.
Materials Index.