Showing papers in "Handbook on The Physics and Chemistry of Rare Earths in 1999"
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TL;DR: In this article, the authors describe the structure types and the crystal chemistry of the ternary (quaternary) germanides of the rare-earth metals and show that the main reason for the formation of such compounds is the presence of components with significantly different crystallochemical properties.
Abstract: Publisher Summary This chapter reviews ternary R–M–Ge systems that have been studied over the entire concentration region but only partly investigated. The character of interaction in these systems varies, and major differences are seen in the number of ternary germanides observed within the investigated concentration range. The chapter describes the structure types and the crystal chemistry of the ternary (quaternary) germanides of the rare-earth metals. The known structures of the germanides belong to 135 structure types. As R and Ge are components with much different crystallochemical properties, the deciding factor that affects the formation, composition, and structure is the nature of the third component in the systems. The main reason for the formation of a large number of ternary compounds in the R–M–Ge systems (M = s or d element) is the presence of components with significantly different crystallochemical properties.
29 citations
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TL;DR: In this article, itinerant electron metamagnetworks of Co sublattice in the lanthanide-cobalt intermetallics were studied and the role of volume effects and spin fluctuation effects on the metamagnetic behavior was discussed.
Abstract: Publisher Summary This chapter discusses itinerant electron metamagnetism of Co sublattice in the lanthanide-cobalt intermetallics. The first-order transition (FOT) is observed in several lanthanide-cobalt (R-Co) intermetallics under the effect of varying external parameters and internal parameters. This transition occurs between a nonmagnetic or low-induced moment state and a ferromagnetic state. This phenomenon is called itinerant electron metamagnetism (IEM). The various models to describe IEM are discussed. At the beginning, the basic concepts of the band theory of metamagnetism describing the magnetically uniform states are presented. Then, the role of volume effects and spin fluctuation effects on the metamagnetic behavior are also briefly introduced. The magnetic properties of the systems consisting of both itinerant electrons and localized spins are formulated on the basis of the s-d model. The experimental overview of IEM is given. This section consists of three major parts. The role of the magnetic R-atom as well as the influence of the 3d electrons affecting the character of the magnetic phase transitions and the spin fluctuation scattering is discussed. High-field magnetization in the RCo 2 with one unstable magnetic sublattice is also discussed. IEM in the RCo 3 - and RCo 5 -based compounds is presented.
27 citations
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TL;DR: A review of the current knowledge concerning the phase diagrams and crystal structures of ternary metal germanides with the R elements can be found in this paper, where the authors describe the isothermal sections and crystallographic characteristics of the compounds and outline the experimental methods that have been utilized.
Abstract: Publisher Summary This chapter reviews the current knowledge concerning the phase diagrams and crystal structures of ternary metal germanides with the R elements. It describes the isothermal sections and crystallographic characteristics of ternary compounds and outlines the experimental methods that have been utilized. While no phase diagram is available for the Ce–Ga–Ge system, the X-ray phase analysis of 180 ternary alloys indicated the formation of four ternary compounds in the Ce–Ga–Ge system. No phase diagram has been constructed for the ternary Ho–A1–Ge system; however, data on the formation and crystal structure of three compounds exist because of the independent investigations of research groups from L’viv University and Geneva University.
25 citations
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TL;DR: In this article, the phase diagrams of binary and ternary Sc-based intermetallics are examined in the entire or partial concentration region for majority of elements, including their composition, melting temperature and crystallographic data.
Abstract: Publisher Summary The phase diagrams of the Sc–E (E = element) binary systems are examined in the chapter in the entire or partial concentration region for majority of elements. The data about all scandium binary intermetallics, including their composition, melting temperature (in °C) and crystallographic data (structure type (ST) or symmetry and lattice parameters) are presented in the chapter. In the chapter, the reference source of the crystallographic data is presented first followed by the references in which these data appear. The chapter presents general trends among the binary and ternary Sc-based intermetallics, because this information may be interesting for the syntheses of new Sc compounds for both basic researches as well as for technical applications.
17 citations
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TL;DR: In this article, the authors discuss X-ray scattering cross-section of lanthanide magnetism, including both resonant and non-resonant cross-sections, and discuss the polarization dependence of the Xray magnetic crosssection.
Abstract: Publisher Summary This chapter discusses x-ray scattering of lanthanide magnetism. The chapter discusses X-ray scattering cross-section, including both resonant and non-resonant cross-sections. The polarization dependence of the X-ray magnetic cross-section is developed, and work through an example of the calculation of the scattering expected from a helix, as found in some of the heavy lanthanides, and discuss the principles behind the separation of spin and orbital contributions to the total moment. The results of X-ray scattering studies of the lanthanide metal Ho is described, while results from the rest of the lanthanide metals are considered. The chapter discusses random alloys, selected compounds, and artificial structures, including superlattices and thin films, with examples chosen to exemplify the benefits of X-ray magnetic scattering. X-ray studies of the lanthanides in particular have produced a great wealth of information. This includes, on the one hand, a deeper insight into the specific magnetic properties of these elements, while on the other; it has allowed general principles of the X-ray scattering cross-section to be both explored and developed. On the theoretical front the salient features of the non-resonant and the resonant cross-sections are now well understood.
8 citations
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TL;DR: In this article, photoelectron spectroscopy (PES) in heavy fermion systems has been discussed and the theoretical aspects of single-impurity model (SIM) and its calculational approximations Guunarsson-Schonhammer (GS), non-crossing approximation (NCA), as well as various screening models and new pairing approaches are discussed.
Abstract: Publisher Summary This chapter discusses photoelectron spectroscopy (PES) in heavy fermion systems. The theoretical aspects of single-impurity model (SIM) and its calculational approximations Guunarsson-Schonhammer (GS), non-crossing approximation (NCA), as well as various screening models and new pairing approaches are discussed. This is followed by a summary of NCA predictions for PES. The recent calculations of the periodic Anderson model and its application to photoemission are discussed. The chapter reviews the single-crystal data, both on Ce and Yb compounds, and test for the applicability of SIM in periodic systems. This is followed by a discussion of data that suggests that at least in Ce compounds the 4f states form very narrow, weakly temperature dependent bands, not inconsistent with the periodic Anderson model (PAM). The chapter considers heavy fermions within the 5f series of elements (primarily U) and emphasizes the similarities with and differences from the 4f series.
5 citations
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TL;DR: In this article, the effects of magnetoelastic interactions in magnetic materials can display themselves in static magnetostriction deformations and in the changing of the magnetic state under mechanical stress.
Abstract: Publisher Summary This chapter discusses properties of lanthanide metals, their alloys and compounds which can be studied using static and alternating mechanical stresses. The effects related to magnetoelastic interactions are discussed. These interactions in magnetic materials can display themselves in static magnetostriction deformations and in the changing of the magnetic state under mechanical stress. The influence of hydrostatic and uniaxial pressure on the transition temperatures of magnetic phase transformations, magnetization, magnetic phase diagrams and spin structures in the lanthanide metals and their alloys, and compounds with 3d transition metals (TM) and nonmagnetic elements is considered. Pressures causing elastic strains without nonreversible deformations are considered. The chapter discusses the sound attenuation and internal friction in lanthanide metals arising from the existence of magnetic order. The anomalies of the elastic constants and moduli in these metals and their alloys and compounds with Fe and Co and their origin are discussed. The influence of commensurate magnetic structures on elastic properties and sound attenuation in lanthanide metals is discussed. The higher-order elastic constants which characterize the anharmonic properties of crystal lattices and explain the dependence on pressure of elastic constants is described in the chapter. The magnetic phase diagrams obtained from magnetization and elastic properties measurements are discussed.
3 citations