Valence Instabilities and Related Narrow-Band PhenomenaRonald D. Parks Those well-intending workers, especially theorists, who have viewed hungrily the mixed valence problem, but have not yet made the bold leap, might be comforted to learn that the Rochester conference left the virginal state of that problem essentially intact. That is not to say that the event was prosaic. Indeed, the conferees exhibited a level of effervescence appropriate to the freshness and challenge of the problem at hand. If the meeting failed to solve major questions, it at least established several guidelines. One is that future experimental efforts, at least on a short time scale, might be spent most profitably on those substances which exhibit consistent, and hence probably intrinsic, behavior from laboratory to laboratory. A recurring message, not always subtle, to the·theorists was that piecemeal approaches to the mixed valence problem, characteristic of much of the work to date, are of limited usefulness. For at the core of the problem one has a melange of boot-strapping interac tions which must be sorted out and dealt with properly. Para phrasing Phil Anderson (see Epilogue), the mixed valence problem is in the same category of problems which are failing to be done in field theory these days. |
Contents
ConfigurationBased Ionic Energy Levels | 3 |
X | 13 |
Kondo Anomalies due to Rare Earth | 17 |
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4f electrons 4f level actinide alloys Anderson model anomaly antiferromagnetic atomic behavior Bucher bulk modulus calculated CeAl3 cerium compounds concentration conduction band conduction electrons configuration coupling crystal field curve decreases density divalent energy entropy exchange excitation experimental Fermi energy Fermi level ferromagnetic function Gd3+ Hamiltonian Holtzberg impurity increase interaction intermediate valence ionic isomer shift kbar Kondo effect lattice constant Lett linear linewidth low temperature magnetic ordering magnetic susceptibility mean field theory mean-field measurements metallic mixed valence Mössbauer neutron observed obtained optical paramagnetic parameter Penney phase boundary phase diagram phase transition phonon Phys plot pressure Proc properties rare earth resistivity resonance samarium sample scattering shown in Fig Sm3+ SmB6 specific heat spectra spin fluctuation splitting temperature dependence term theory thermal tion Tm2+ Tm3+ TmSe TmTe Tournier trivalent valence fluctuations Varma width Wohlleben zero