Magnetism / Magnetismus

ISBN-13: 9783642461347 / Angielski / Miękka / 2012 / 592 str.

Henricus P. J. Wijn

Opis

13 17 has to contain at least 10 spins at a temperature of 1 oK to obtain useful results 10 11 as compared with claims of 10 to 10 spins for the modern resonance saturation techniques under equivalent circumstances. This enormous difference can be traced back to two causes: the ratio of the quality factors of the resonant cavity 4 ('" 1 0 ) and the coils used at audio and sub-audio frequencies (;S 1) and the ratio of the resonance and relaxation absorption coefficients (oc X") that are actually measured. Comparing (4. 25) with (5. 5 ...8) one finds that this last factor is of the orderofHIL1 H, the quotient of the external field and the linewidth of the resonance 2 3 line. This ratio is of the order 10 for concentrated samples, to 10 for diluted samples. Literature. Steady state saturation techniques. ESCHEN FELDER, A. H. , and R. T. WEIDNER: Phys. Rev. 92, 869 (1953). BOLGER, B. : Proc. Koninkl. Ned. Akad. Wetenschap B 62,348 (1959); - Thesis Leiden 1959. Pulse saturation techniques. GIORDMAINE, J. A. , L. E. ALSOP, F. R. NASH, and C. H. TOWNES: Phys. Rev. 109, 302 (1958). DAVIS jr. , F. C. , M. W. P. STRANDBERG, and R. L. KVHL: Phys. Rev. 111, 1268 (1958). BOWERS, K. D. , and W. B. MIMS: Phys. Rev. 115, 285 (1959). DREWES, G. W. J. : Thesis Leiden 1967. Other resonance techniques.

Spis treści

Paramagnetic Relaxation.- A. Introduction.- I. Paramagnetic relaxation.- a) Paramagnetism.- b) Phenomenological theories.- II. Experimental methods.- B. Spin-spin relaxation.- I. General theory.- II. Applications of the general theory.- a) Hz = Hex = 0.- b).Hel = 0.- c).Hel ? 0.- III. Cross-relaxation.- C. Spin-lattice relaxation.- I. Transition probabilities and relaxation times.- II. Field and temperature dependence of relaxation mechanisms.- III. Relaxation due to spin-orbit coupling.- a) Rare-earth salts.- b) Spin-lattice relaxation of the iron group transition elements.- c) Numerical parameters.- d) Anisotropy in relaxation times.- e) Relaxation in S-state ions.- f) Crystal bonding.- IV. Relaxation due to alternative perturbations.- V. Relaxation in the phonon system.- General references.- Electron Spin Resonance.- I. General principles.- II. Parameters associated with electron resonance spectra.- III. Experimental technique.- IV. Basic absorption processes.- V. g-values and their theoretical interpretation.- VI. The Spin Hamiltonian.- VII. Hyperfine splitting and the Spin Hamiltonian.- VIII. Examples of spectrum analysis.- IX. General conclusion.- Structural Information from Paramagnetic Resonance.- A. Introduction.- I. Types of systems studied.- II. The g-tensor.- III. Hyperfine splitting.- B. Free radicals.- I. ?-radicals.- II. ?-radicals.- C. Triplet state systems and biradicals.- I. Introduction.- II. Resonant behavior of triplet systems.- III. Ground state triplet species.- IV. Biradicals.- D. Defects in insulating solids.- I. Electron excess centers.- II. Electron-deficient centers.- III. Other defects in insulators.- E. Defects in semiconductors.- I. Compounds.- F. Miscellaneous topics.- I. ESR of gases.- II. Transition metal ions in liquid solution.- III. Generation of odd-electron centers.- IV. Sources of error.- V. Special techniques.- General references.- Austauschwechselwirkung in Isolatoren.- Einführung.- A. Die Theorie des Wasserstoffmoleküls in der Heitler-London-Näherung.- B. Die direkte Austauschwechselwirkung.- I. Die Verallgemeinerung der Heitler-London-Methode auf den Kristall..- II. Das Vektormodell von Dirac und van Vleck.- III. Das Vektormodell bei orthogonalisierten Wellenfunktionen.- C. Die indirekte Austauschwechselwirkung.- IV. Der Superaustausch nach Kramers und Anderson.- a) Das Problem der drei Zentren und vier Elektronen. Orthogonale Bahnen.- b) Das Problem der drei Zentren und vier Elektronen. Nichtorthogonale Bahnen.- c) Die Verallgemeinerung auf den Kristall.- V. Der neue Lösungsweg Andersons für das Problem der indirekten Wechselwirkung.- D. Die Austauschwechselwirkung und die Wellenfunktionen der Elektronen im Kristall.- Magnetic Semiconductors.- A. Preface.- I. General remarks.- II. Novel features.- III. Organization of this article.- B. Problems related to the electron band structure of magnetic materials.- I. The one-electron band model of semiconductors.- II. Localized electrons and magnetic moments.- C. Theory of electron transport properties.- I. Magnetic insulators, the Mott transition, and the two types of energy gap.- II. Band structure of rare earth semiconductors.- III. Conductivity properties of magnetic semiconductors.- D. Theory of indirect exchange.- E. Electron orbitals and energies in rare earth ions.- F. Optical properties of crystals.- I. Crystalline field effects on 4 f electrons.- II. The 5 d orbitals in lanthanides.- III. Spectroscopy of exchange interactions.- G. Experimental evidence for indirect exchange.- I. Metallic and insulating rare earth materials.- II. Magnetic interaction via semiconducting carriers.- H. Electrical properties of magnetic semiconductors.- I. The phase diagram of correlated electrons.- II. Electrical properties of 3 d-semiconductors.- III. Rare earth chalcogenides.- Sachverzeichnis (Deutsch-Englisch).- Subject Index (English-German).