Magnetism in Heavy Fermion Systems is a review volume which covers an important subset of topics in the field of heavy fermion and non-Fermi liquid physics. It summarizes much of the experimental information in these areas, and includes an article which discusses theoretical interpretations of the complex magnetic behavior of heavy fermion systems. The topics covered include heavy fermion superconductivity, muon spin relaxation in small-moment heavy fermions, neutron scattering from heavy fermions, random localized magnetism in heavy fermions, and magnetism in Pr-containing cuprates. One feature of the book which should be helpful to graduate students and new workers in the field is the extensive references and a separate list of review articles.

The book on Heavy-Fermion Systems is a part of the Book series "Handbook of Metal Physics", each volume of which is written to facilitate the research of Ph.D. students, faculty and other researchers in a specific area. The Heavy-Fermions (sometimes known as Heavy-Electrons) is a loosely defined collection of intermetallic compounds containing rare-earth (mostly Ce) or actinide (mostly U) elements. These unusual names were given due to the large effective mass (100-1,000 times greater than the mass of a free electron) below a critical temperature. They have a variety of ground states including superconducting, antiferromagnetic, paramagnetic or semiconducting. Some display unusual magnetic properties such as magnetic quantum critical point and metamagnetism. This book is essentially a summary as well as a critical review of the theoretical and experimental work done on Heavy Fermions. · Extensive research references. · Comprehensive review of a very rapidly growing number of theories. · Summary of all important experiments. · Comparison with other highly correlated systems such as High-Tc Superconductors. · Possible Technological applications.

Magnetism in Heavy Fermion Systems is a review volume which covers an important subset of topics in the field of heavy fermion and non-Fermi liquid physics. It summarizes much of the experimental information in these areas, and includes an article which discusses theoretical interpretations of the complex magnetic behavior of heavy fermion systems. The topics covered include heavy fermion superconductivity, muon spin relaxation in small-moment heavy fermions, neutron scattering from heavy fermions, random localized magnetism in heavy fermions, and magnetism in Pr-containing cuprates. One feature of the book which should be helpful to graduate students and new workers in the field is the extensive references and a separate list of review articles.

A large variety of materials prove to be fascinating in solid state and condensed matter physics. New materials create new physics, which is spearheaded by the international experimental expert, Prof Yoshichika Onuki. Among them, the f electrons of rare earth and actinide compounds typically exhibit a variety of characteristic properties, including spin and charge orderings, spin and valence fluctuations, heavy fermions, and anisotropic superconductivity. These are mainly manifestations of better competitive phenomena between the RKKY interaction and the Kondo effect. The present text is written so as to understand these phenomena and the research they prompt. For example, superconductivity was once regarded as one of the more well-understood many-body problems. However, it is, in fact, still an exciting phenomenon in new materials. Additionally, magnetism and superconductivity interplay strongly in heavy fermion superconductors. The understanding of anisotropic superconductivity and magnetism is a challenging problem in solid state and condensed matter physics. This book will tackle all these topics and more.

Contents: Spin Fluctuations in Heisenberg Magnets: Dynamic Critical Phenomena and Excitations in Quasi-Periodic Systems (S W Lovesey)Quenching of Spin Fluctuations by High Magnetic Fields (K Ikeda et al.)Kondo Effect and Heavy Fermions (B Coqblin et al.)Magnetic Interactions in Correlated Electron Systems: High Pressure Investigations (J D Thompson)Hall Effect in Heavy Fermion and Mixed Valence Systems (A Hamzić & A Fert)Magnetic Properties of Uranium Based 1-2-2 Intermetallics (T Endstra et al.)Inelastic Magnetic Excitations in Anomalous Rare Earth Intermetallics (E Holland-Moritz)Neutron Scattering Studies of Magnetic Properties of Actinide Systems (G H Lander & G Aeppli)Magnetic Properties of Heavy Fermion Systems — As Studied by μSR-Spectroscopy (A Schenck)Re-Entrant Spin-Glasses: Do They Exist? (B R Coles & S B Roy)Insulating Spin Glass Systems (J K Srivastava)Nuclear Magnetism in Metals and Alloys (S Ramakrishnan & G Chandra) Readership: Solid-state physicists and chemists. keywords:

For more than 30 years the investigation of heavy-fermion (HF) metals has been one of the most fascinating and interesting fields in condensed matter physics both experimentally and theoretically. The HF phenomenon is observed in compounds containing rare-earth elements such as, e.g., Ce or Yb. The ground-state properties of these systems is considered to result from a competition between the Kondo effect and the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. The Kondo effect induces a screening of the local 4f moments by the conduction electrons and, thus, favors a nonmagnetic ground state. By contrast, the indirect RKKY interaction promotes a magnetic ordering of the local moments. Therefore, depending on the strength of these interactions, the ground state of a HF compound ranges from paramagnetic (PM) to magnetically ordered. Even interplay between magnetism and superconductivity is observed in some materials. High-pressure experiments are of particular interest because for a given system the ground state can be tuned by external pressure (p). In the case of Yb-based Kondo-lattice systems, pressure stabilizes the magnetic state, while for Ce-based Kondo-lattice compounds pressure favors a non-magnetic ground state. Therefore, pressure is an ideal tool to tune a HF material through a zero-temperature magnetic instability in order to study quantum critical behavior in its vicinity. The present thesis addresses the effect of pressure, magnetic field, and temperature on the properties of the rare-earth compounds Yb(Rh0.94Ir0.06)2Si2, YbIr2Si2, and CeRuPO. Electrical resistivity measurements under pressure have been performed in order to investigate the evolution of the ground-state properties and to search for the putative QCP supposed to exist in the studied HF materials. At atmospheric pressure, Yb(Rh0.94Ir0.06)2Si2 does not order down to 20mK. Applying a small pressure, AFM order is observed at low temperatures. Upon further increasing pressure, the magnetic transition temperature increases, and a second magnetic transition appears inside the ordered state. The electrical resistivity measurements under pressure suggest that, at ambient pressure, Yb(Rh0.94Ir0.06)2Si2 orders slightly below 20 mK. The T- p phase diagram of Yb(Rh0.94Ir0.06)2Si2 and of YbRh2Si2 can be superposed by shifting the pressure axis of Yb(Rh0.94Ir0.06)2Si2 by ?p = -0.06 GPa. The electrical resistivity studies indicate that in Yb(Rh0.94Ir0.06)2Si2, Ir substitution acts primarily as negative chemical pressure and disorder effects play only a minor role. The results point at the existence of a pressure (volume) controlled quantum critical point (QCP) at a hypothetical negative critical pressure of pc = -0.25GPa. The ambient-pressure thermodynamic and transport properties of YbRh2Si2 reveal a PM ground state, in contrast to the Rh-homolog which possesses a magnetic ground state being situated in the direct vicinity to an AFM QCP. Application of pressure on YbRh2Si2 is expected to tune the system through a QCP, providing a unique opportunity to investigate the physical properties at and around a pressure (volume) controlled magnetic QCP in a clean stoichiometric Yb system. The Landau Fermi-liquid (LFL) state observed at low temperatures at ambient pressure survives in the pressure range up to pLFLc ÷ 3 GPa. With further increasing pressure, the resistivity shows a temperature dependence weaker than quadratic. This, so-called, non Fermi-liquid (NFL) behavior observed down to the lowest temperatures extends up to the critical pressure, pc ÷ 8 GPa, where magnetic order sets in. This broad region of NFL behavior might reveal the existence of a novel type of metallic phase. The magnetic order develops suddenly hinting at a first-order transition at pc. With further increasing pressure, the magnetic state is stabilized. The high-T resistivity studies allow to determine the pressure evolution of the Kondo and crystalline electric field (CEF) energy scales. In the PM region, the CEF splitting is independent of p, while TK decreases exponentially in the same pressure range. At about the critical pressure, a low-lying Kondo scale and the excited CEF levels at higher temperatures can be clearly resolved. At ambient pressure CeRuPO is a FM Kondo-lattice system with TC = 14 K and TK ÷ 10 K. So far, the behavior at a FM QCP in a Kondo-lattice system is not settled. Therefore, pressure studies on CeRuPO offer the great opportunity to investigate the suppression of FM order in a Ce-based Kondo-lattice system. Upon applying pressure the magnetic ordering temperature in CeRuPO shifts toward lower temperatures. Furthermore, the ground state of CeRuPO changes from FM to AFM order at p* ÷ (0.87 ö 1.01) GPa. Our results indicate a critical pressure of pc ÷ 3 GPa where the magnetic transition temperature is suppressed to zero temperature in a first-order like way. Therefore, we come to the conclusion that a magnetic QCP does not exist in CeRuPO. Beyond pc, LFL behavior was observed at low temperatures, in support of our previous conclusion. The pressure evolution of the high-T electrical resistivity cannot be understood in a simple picture for a Ce-based HF metal considering a dominant Kondo energy scale. At low pressures, the temperature dependence of the resistivity above the magnetic transition is strongly affected by the Kondo effect, magnetic fluctuations, and CEF splitting. At higher pressures, the contribution to ?(T) from Kondo scattering on the ground state and on excited CEF levels can be separated. Our study indicates that CeRuPO is a further example of a FM system in which application of pressure suppresses the magnetic order, but also destabilizes FM order in favour of an AFM one, preventing the appearance of a FM QCP.

The behaviour of magnetic impurities in metals has posed problems to challenge the condensed matter theorist over the past 30 years. This book deals with the concepts and techniques which have been developed to meet this challenge, and with their application to the interpretation of experiments. This book will be of interest to condensed matter physicists, particularly those interested in strong correlation problems. The detailed discussions of advanced many-body techniques should make it of interest to theoretical physicists in general.