Elsevier, 2009. 464 p. ISBN: 978-0-08-054814-2
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 18 of this Handbook series.
In Chapter 1 of Volume 18 of this Handbook, a review of the filled skutterudites is given. The skutterudites are derived from a class of wellknown compounds characterized by the chemical formula TX3 where the transition metal T ? Co, Rh, Ir and the pnictogen X ? P, As, Sb. These materials have attracted much interest during the past three decades due to the wide variety of their electronic and magnetic phenomena, including their promising thermoelectric properties. The filled skutterudites,
described in Chapter 1, are structurally closely related to the normal skutterudites and have the chemical formula MT4X
12. The ‘‘filler’’ atom M comprises the elements La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, U, and Th, the transition metal T mainly including the elements Fe, Ru, and Os. The interest in the filled skutterudites originates from the fact that they display an immense variety of correlated electron phenomena. These phenomena include spin fluctuations, itinerant electron ferromagnetism,
local moment ferromagnetism, antiferromagnetism, heavy-fermion behavior, non-Fermi-liquid behavior, Kondo behavior and also conventional BCS superconductivity, unconventional superconductivity, and even
hybridization gap semiconducting behavior. Needless to say that the large reservoir of structurally similar compounds that can be obtained by varying the components M, T, and X has provided an almost ideal testing ground for many theoretical models. Many of these compounds do not form easily and in order to obtain single-phase materials considerable experimental expertise is required. For this reason the authors of Chapter 1 have included a section dealing with the synthesis of the filled skutterudites.
Chapter 2 of this Handbook Volume deals with spin dynamics in nanometric magnetic systems. It is emphasized that ferromagnetic resonance (FMR) is a powerful experimental tool in the study of the
magnetic properties of ferromagnetic materials and can be applied to the entire range of materials, from bulk ferromagnetic and ferrimagnetic crystals to magnetic thin films and multilayers. More recently, it has also been used to characterize nanogranular and nanoparticle systems. FMR is an excellent method for the evaluation of magnetic properties in low-dimensional structures or nanometric systems indeed. The FMR technique provides a simple method for measuring the effective magnetic field inherent in a
given spin system. In this chapter the author first discusses the basic elements of FMR theory, in particular those that are relevant for a general understanding when this technique is applied to nanometric systems. An outline is given of the main quantities that are necessary to deal with nanometric systems, by considering the various components which make up the free energy of the magnetic systems, and hence its effective field. Specific cases of surface anisotropy and interparticle interactions are discussed in detail since they are of particular importance in nanometric systems. The author stresses how mainly in the last decade a number of novel developments have taken place in experimental techniques that have been used to measure magnetization dynamics. These developments
include: pump-probe or femtosecond spectroscopy, pulse generation, scanning probe (cantilever) FMR, network analyzer FMR, bolometric detection of FMR, and high-frequency electrical measurements of
magnetodynamics. Many of these techniques are easily adaptable to nanometric systems or were acrually developed for the purpose of measuring magnetization dynamics in nanometric structures. These
techniques are mainly based on the delivery of the high-frequency excitation signal to the sample, usually through a microstripline upon which the sample is located. Much of these advances are a direct consequence of the need to study ever smaller sized magnetic structures and their temporal
response, with particular emphasis on ultrafast dynamics as involved in mode applications in the fields of telecommunication and data storage. A discussion of some of these techniques is included in this chapter. Hand in hand with the development of novel techniques, very extensive numerical
calculations have been performed on nanometric systems and for obvious reasons the author has outlined some of the main approaches that have been used. For instance, there has been an enormous research effort based on the dynamical effects of spin current on the magnetization state in nanostructured elements and multilayers. Here the effect of transfer of spin angular momentum, and spin and charge accumulation effects play an important role. Because of the importance of spin torque transfer effects in data storage systems, the author has included in his chapter a discussion of some of the main details of these effects from both the experimental and the theoretical points of view.
In the last chapter of this volume of the Handbook a review is given of the various types of magnetic sensors nowadays available, including a discussion of the materials and principles that have been used for their construction. Sensors play an ever important role in our daily life, in the personal as well in the industrial sphere. Of all sensors, magnetic sensors take the most prominent position. The term magnetic sensor is actually used in at least two different ways. The most common type of magnetic sensor refers to cases where one wishes to probe magnetic fields of various origins, from the Earth’s magnetic field to the stray fields produced by bits of magnetically stored information. In these cases the materials of which the sensor is composed need not necessarily be magnetic. By contrast, the magnetic sensors of the second type include sensors that use magnetic materials or magnetic principles. They may be exploited for measuring either magnetic or nonmagnetic quantities. Usually the first meaning of the
term magnetic sensor is used without explicitly specifying that it serves for sensing or measuring a magnetic field. By far most of the produced magnetic sensors are devices based on the Hall effect. These are semiconductor sensors which are cheap and can be made of small size, but their resolution and stability is very limited. If higher accuracy is desired, soft magnetic materials are generally employed, either as yoke, as field concentrator, or as functional element. The fast development of
ferromagnetic magnetoresistors used in mode magnetic reading heads has led to the appearance of devices based on similar principles also on the sensor market. Although such sensors based on magnetic thin films or multilayers are much more sensitive than Hall sensors, their performance is still limited. Sensors with cores, yokes, or field concentrators made of bulk magnetic material are more sensitive and stable than thin-film sensors. As outlined by the author in this chapter, the most critical parameter for
magnetic sensors is hardly the sensitivity, because amplification is relatively inexpensive. Nonlinearity and temperature dependence of sensitivity is equally important but it can often be suppressed by a feedback. Noise matters, but usually the most serious problems of sensors containing magnetic material are remanence, cross-field sensitivity, and temperature stability of offset. All these items are addressed by the author in his chapter, including the general trend of miniaturization and integration of electronic
elements. A specific comparison is made between traditional miniature fluxgates using wire cores based on the longitudinal fluxgate effect and sensors using the transverse fluxgate effect or sensors based on the giant magnetoimpedance effect. Also an overview of magnetic sensors for mechanical quantities is presented, with special emphasis given on torque sensors.
Volume 18 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 18 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.
Preface to volume 18.
Contributors.
Magnetic Properties of Filled Skutterudites.
Spin Dynamics in Nanometric Magnetic Systems.
Magnetic Sensors: Principles and Applications.
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 18 of this Handbook series.
In Chapter 1 of Volume 18 of this Handbook, a review of the filled skutterudites is given. The skutterudites are derived from a class of wellknown compounds characterized by the chemical formula TX3 where the transition metal T ? Co, Rh, Ir and the pnictogen X ? P, As, Sb. These materials have attracted much interest during the past three decades due to the wide variety of their electronic and magnetic phenomena, including their promising thermoelectric properties. The filled skutterudites,
described in Chapter 1, are structurally closely related to the normal skutterudites and have the chemical formula MT4X
12. The ‘‘filler’’ atom M comprises the elements La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, U, and Th, the transition metal T mainly including the elements Fe, Ru, and Os. The interest in the filled skutterudites originates from the fact that they display an immense variety of correlated electron phenomena. These phenomena include spin fluctuations, itinerant electron ferromagnetism,
local moment ferromagnetism, antiferromagnetism, heavy-fermion behavior, non-Fermi-liquid behavior, Kondo behavior and also conventional BCS superconductivity, unconventional superconductivity, and even
hybridization gap semiconducting behavior. Needless to say that the large reservoir of structurally similar compounds that can be obtained by varying the components M, T, and X has provided an almost ideal testing ground for many theoretical models. Many of these compounds do not form easily and in order to obtain single-phase materials considerable experimental expertise is required. For this reason the authors of Chapter 1 have included a section dealing with the synthesis of the filled skutterudites.
Chapter 2 of this Handbook Volume deals with spin dynamics in nanometric magnetic systems. It is emphasized that ferromagnetic resonance (FMR) is a powerful experimental tool in the study of the
magnetic properties of ferromagnetic materials and can be applied to the entire range of materials, from bulk ferromagnetic and ferrimagnetic crystals to magnetic thin films and multilayers. More recently, it has also been used to characterize nanogranular and nanoparticle systems. FMR is an excellent method for the evaluation of magnetic properties in low-dimensional structures or nanometric systems indeed. The FMR technique provides a simple method for measuring the effective magnetic field inherent in a
given spin system. In this chapter the author first discusses the basic elements of FMR theory, in particular those that are relevant for a general understanding when this technique is applied to nanometric systems. An outline is given of the main quantities that are necessary to deal with nanometric systems, by considering the various components which make up the free energy of the magnetic systems, and hence its effective field. Specific cases of surface anisotropy and interparticle interactions are discussed in detail since they are of particular importance in nanometric systems. The author stresses how mainly in the last decade a number of novel developments have taken place in experimental techniques that have been used to measure magnetization dynamics. These developments
include: pump-probe or femtosecond spectroscopy, pulse generation, scanning probe (cantilever) FMR, network analyzer FMR, bolometric detection of FMR, and high-frequency electrical measurements of
magnetodynamics. Many of these techniques are easily adaptable to nanometric systems or were acrually developed for the purpose of measuring magnetization dynamics in nanometric structures. These
techniques are mainly based on the delivery of the high-frequency excitation signal to the sample, usually through a microstripline upon which the sample is located. Much of these advances are a direct consequence of the need to study ever smaller sized magnetic structures and their temporal
response, with particular emphasis on ultrafast dynamics as involved in mode applications in the fields of telecommunication and data storage. A discussion of some of these techniques is included in this chapter. Hand in hand with the development of novel techniques, very extensive numerical
calculations have been performed on nanometric systems and for obvious reasons the author has outlined some of the main approaches that have been used. For instance, there has been an enormous research effort based on the dynamical effects of spin current on the magnetization state in nanostructured elements and multilayers. Here the effect of transfer of spin angular momentum, and spin and charge accumulation effects play an important role. Because of the importance of spin torque transfer effects in data storage systems, the author has included in his chapter a discussion of some of the main details of these effects from both the experimental and the theoretical points of view.
In the last chapter of this volume of the Handbook a review is given of the various types of magnetic sensors nowadays available, including a discussion of the materials and principles that have been used for their construction. Sensors play an ever important role in our daily life, in the personal as well in the industrial sphere. Of all sensors, magnetic sensors take the most prominent position. The term magnetic sensor is actually used in at least two different ways. The most common type of magnetic sensor refers to cases where one wishes to probe magnetic fields of various origins, from the Earth’s magnetic field to the stray fields produced by bits of magnetically stored information. In these cases the materials of which the sensor is composed need not necessarily be magnetic. By contrast, the magnetic sensors of the second type include sensors that use magnetic materials or magnetic principles. They may be exploited for measuring either magnetic or nonmagnetic quantities. Usually the first meaning of the
term magnetic sensor is used without explicitly specifying that it serves for sensing or measuring a magnetic field. By far most of the produced magnetic sensors are devices based on the Hall effect. These are semiconductor sensors which are cheap and can be made of small size, but their resolution and stability is very limited. If higher accuracy is desired, soft magnetic materials are generally employed, either as yoke, as field concentrator, or as functional element. The fast development of
ferromagnetic magnetoresistors used in mode magnetic reading heads has led to the appearance of devices based on similar principles also on the sensor market. Although such sensors based on magnetic thin films or multilayers are much more sensitive than Hall sensors, their performance is still limited. Sensors with cores, yokes, or field concentrators made of bulk magnetic material are more sensitive and stable than thin-film sensors. As outlined by the author in this chapter, the most critical parameter for
magnetic sensors is hardly the sensitivity, because amplification is relatively inexpensive. Nonlinearity and temperature dependence of sensitivity is equally important but it can often be suppressed by a feedback. Noise matters, but usually the most serious problems of sensors containing magnetic material are remanence, cross-field sensitivity, and temperature stability of offset. All these items are addressed by the author in his chapter, including the general trend of miniaturization and integration of electronic
elements. A specific comparison is made between traditional miniature fluxgates using wire cores based on the longitudinal fluxgate effect and sensors using the transverse fluxgate effect or sensors based on the giant magnetoimpedance effect. Also an overview of magnetic sensors for mechanical quantities is presented, with special emphasis given on torque sensors.
Volume 18 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 18 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.
Preface to volume 18.
Contributors.
Magnetic Properties of Filled Skutterudites.
Spin Dynamics in Nanometric Magnetic Systems.
Magnetic Sensors: Principles and Applications.
Author index.
Subject index.
Materials index.