Dynamics of Localized Moments in Metals. II. Second-Order Exchange Effects

Orbach, Raymond Lee; Spencer, H. J.

doi:10.1103/physrev.179.690

Cited by 30 publications

(2 citation statements)

References 20 publications

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“…The obvious test would be to follow the muon Knight shifts to high temperature. In a useful formulation due to Orbach (1975), the switch from Boltzmann to Fermi-Dirac character results simply from detailed balance in the spin exchange between localized and itinerant electrons, together with their respective spin-lattice relaxation. A bound state must also lose its identity, so that a hyperfine constant cannot be defined, if it is exchanged before a classical orbit is completed.…”

Section: The Question Of Screening Versus Bindingmentioning

confidence: 99%

Muonium as a model for interstitial hydrogen in the semiconducting and semimetallic elements

2009

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Although the interstitial hydrogen atom would seem to be one of the simplest defect centres in any lattice, its solid state chemistry is in fact unknown in many materials, not least amongst the elements. In semiconductors, the realization that hydrogen can profoundly influence electronic properties even as a trace impurity has prompted its study by all available means-but still only in the functionally important or potentially important materials-for the elements, Si, Ge and diamond. Even here, it was not studies of hydrogen itself but of its pseudo-isotope, muonium, that first provided the much needed microscopic pictures of crystallographic site and local electronic structure-now comprehensively confirmed by ab initio computation and such data as exists for monatomic, interstitial hydrogen centres in Si. Muonium can be formed in a variety of neutral paramagnetic states when positive muons are implanted into non-metals. The simple trapped atom is commonly only metastable. It coexists with or reacts to give defect centres with the unpaired electron in somewhat more extended orbitals. Indications of complete delocalization into effective mass states are discussed for B, α-Sn, Bi and even Ge, but otherwise all the muonium centres seen in the elemental semiconductors are deep and relatively compact. These are revealed, distinguished and characterized by µSR spectroscopy-muon spin rotation and resonance informing on sites and spin-density distributions, muon spin relaxation on motional dynamics and charge-state transitions.This Report documents the progress of µSR studies for all the semiconductors and semimetals of the p-block elements, Groups III-VI of the Periodic Table . The striking spectra and originally unanticipated results for Group IV are for the most part well known but deserve summarizing and updating; the sheer diversity of muonium states found is still remarkable, especially in carbon allotropes. The interplay of crystallographic site and charge state in Si and Ge at high temperatures, or under illumination, reflects the capture and loss of charge carriers that should model the electrical activity of monatomic hydrogen but still challenges theoretical descriptions. Spin-flip scattering of conduction electrons by the paramagnetic centres is revealed in heavily doped n-type material, as well as some modification of the local electronic structures. The corresponding spectroscopy for the solid elements of Groups III, V and VI is rather less well known and is reviewed here for the first time; a good deal of previously unpublished data is also included. Theoretical expectations and computational modelling are sparse, here. Recent results for B suggest a relatively shallow centre with molecular character; P and As show deeper quasi-atomic states, but still with substantial overlap of spin density onto surrounding host atoms. Particular attention is paid to the chalcogens. Muonium centres in Te show charge-state transitions already around room temperature; the identification of those in S and Se has been compli...

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Section: The Question Of Screening Versus Bindingmentioning

confidence: 99%

Muonium as a model for interstitial hydrogen in the semiconducting and semimetallic elements

2009

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“…Korringa, em 1950, foi o primeiro a levar em consideração a interação de troca para calcular o tempo de relaxação no caso de relaxação nuclear em metais. Em analogia com esse caso, Orbach e Spencer [113] e Burr e Orbach [114], usando em lugar da interação hiperfina a interação de troca entre elétrons de condução e momentos localizados dada pela equação 2.41 (ver subseção 2.4.2), obtiveram uma expressão para a taxa de relaxação do momento localizado para elétrons de condução dada por 2.37: Da equação 2.37, temos que a taxa de relaxação de Korringa depende linearmente da temperatura e embora tenha sido obtida partindo de um modelo muito simplificado para o metal, como é o caso de considerar os elétrons de condução como elétrons livres, esta dependência com T é preservada numa dedução mais completa em que se inclua, por exemplo, a interação de troca entre elétrons de condução [114] ou, se em lugar de supor o parâmetro de troca constante, o considerarmos como o valor médio de J(k-k ′ ) sobre a superfície de fermi [115].…”

Section: Relaxação Korringaunclassified

Ressonância de spin eletrônico (ESR) em sistemas de dimensões reduzidas

Iwamoto¹

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DedicatóriaÀ minha esposa Ana Priscila e à minha filha Lara, dedico. AgradecimentosA realização desta tese de doutorado não seria a mesma sem a contribuição, direta e indireta, de muitas pessoas. Por essa razão, desejo expressar os meus sinceros agradecimentos: Ao Prof. Pascoal Pagliuso, meu orientador, pela competência científica e acompanhamento do trabalho, pelo inestimável apoio na minha preparação dos exames, nas críticas, correções e sugestões, pela disponibilidade e pela amizade. Não poderia deixar de mencionar a sua paciência e incentivo com que conduziu a minha formação ao longo de desses anos.Ao Prof. Rettori, pela amizade, ensinamentos, valiosas discussões, e principalmente pela paciência, que sempre esteve disponível para discutir problemas relacionados à física.Ao Dr. Marcelo Vargas, que me ensinou a sintetizar as amostras de nanopartículas e me apresentou às técnicas de microscopias.Não poderia deixar de agradecer ao Prof. Humberto e Dr. Douglas, da faculdade de Ciências -Unesp-Bauru, pelo fornecimento dos filmes finos amorfos usados nesse trabalho, ao Centro de Spintrônica e computação quântica (Center of Spintronics and Quantum Computation) da Universidade da Califórnia de Santa Bárbara, (USA) que forneceram os filmes cristalinos de GaAs dopados com Mn ao nosso grupo pelo Prof.

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Homogeneous dynamical susceptibilities of dilute magnetic alloys

Götze

Wölfle

1972

J Low Temp Phys

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Dynamics of Localized Moments in Metals. II. Second-Order Exchange Effects

Cited by 30 publications

References 20 publications

Muonium as a model for interstitial hydrogen in the semiconducting and semimetallic elements

Muonium as a model for interstitial hydrogen in the semiconducting and semimetallic elements

Ressonância de spin eletrônico (ESR) em sistemas de dimensões reduzidas

Homogeneous dynamical susceptibilities of dilute magnetic alloys

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