Analysis of Magnetic After-Effects in Manganese Ferrites

Walz, F.; Rivas, J.; Brabers, J.H.V.J.; Kronmüller, H.

doi:10.1002/(sici)1521-396x(199906)173:2<467::aid-pssa467>3.0.co;2-2

Cited by 7 publications

(30 citation statements)

References 37 publications

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“…Complementarily, the reaction of the MAE spectra of polycrystalline Fe 3 O 4 on systematically doping with (i) B-site vacancies (Fe 3−δ O 4 ) [120][121][122][123][124] or impurity ions (Fe 3−x M x O 4 ) like M = Mn 2+ [122,212], Ba 2+ [213], Ni 2+ [214], Zn 2+ [215,216], Ti 4+ [217,218], Ga 3+ [219] has been investigated. The basic effects of these treatments may be summarized as follows (section 3.2.4(3)):…”

Section: Mae Contributions To Model Designingmentioning

confidence: 99%

The Verwey transition - a topical review

Walz¹

2002

J. Phys.: Condens. Matter

698

663

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This review encompasses the story of the Verwey transition in magnetite over a period of about 90 years, from its discovery up to the present. Despite this long period of thorough investigation, the intricate multi-particle system Fe3O4 with its various magneto-electronic interactions is not completely understood, as yet - although considerable progress has been achieved, especially during the last two decades. It therefore appeared appropriate to subdivide this retrospect into three eras: (I) from the detection of the effect to the Verwey model (1913-1947), being followed by a period of: (II) checking, questioning and modification of Verwey's original concepts (1947-1979). Owing to prevailing under-estimation of the role of crystal preparation and qualitiy control, this period is also characterized by a series of uncertainties and erroneous statements concerning the reaction order (one or two) and type of the transition (multi-stage or single stage). These latter problems, beyond others, could definitely be solved within era (III) (1979 to the present) - in favour of a first-order, single-stage transition near 125 K - on the basis of experimental and theoretical standards established in the course of a most inspiring conference organized in 1979 by Sir Nevill Mott in Cambridge and solely devoted to the present topic. Regarding the experimental field of further research, the remarkable efficiency of magnetic after-effect (MAE) spectroscopy as a sensitive probe for quality control and investigation of low-temperature (4 KTv) into a Wigner crystal (T

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Section: Mae Contributions To Model Designingmentioning

confidence: 99%

The Verwey transition - a topical review

Walz¹

2002

J. Phys.: Condens. Matter

698

663

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“…Within the high-temperature range (T V < T 500 K), in nonstoichiometric crystals a second type of charge transfer processes-described in terms of relations (2)-is feasible, originating from thermally activated B-site vacancy-mediated diffusion of intrinsic and/or substituted foreign ions. Indeed, most of the MAE spectra occurring above T V in imperfect magnetite and related compounds are induced from ionic processes following such type- (2) mechanisms [8][9][10][11][12], cf figure 6(b).…”

Section: Introductionmentioning

confidence: 99%

Stress-induced relaxation mechanisms in single-crystalline titanomagnetites

Walz¹,

Brabers

et al. 2003

J. Phys.: Condens. Matter

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“…1, 2) from lowest temperatures (T < 4 K), down to a plateau of minute strength, extending between 55 and 75 K, thereby surpassing a Debye-type maximum near 50 K of annealing-depending strength. This behaviour is at variance to that of e À -irradiated stoichiometric magnetite where, immediately after irradiation, the corresponding tunneling zone is found to be strongly suppressed [15]; it ressembles, however, that of magnetite compounds submitted to charge-order perturbations by quenching-in of octahedral vacancies [29 to 31] or doping with ionic impurities like Ti 4 [32,33], Ga 3 [34], Mn 2 [35,36], etc.…”

Section: The Mae Spectrum Of Electron-irradiated Yigmentioning

confidence: 61%

Charge Transport Mechanisms in Single Crystalline Yttrium Iron Garnet as Resolved by Magnetic Relaxations

Walz¹,

Torres

Íñiguez

et al. 2000

phys. stat. sol. (a)

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Single crystalline Yttrium Iron Garnet (YIG) has been irradiated at T % 80 K with 3 MeV electrons to a dose of ! 10 19 e À cm À2 and the recovery of the induced lattice damages, after systematic annealing over the temperature range 80 K < T a < 1400 K, is carefully investigated by means of magnetic after-effect (MAE) spectroscopy, covering the range 4 K < T < 500 K. The wide extension of recovery is attributed, besides to Fe 3 and Fe 2 interstitials and their associated d-and a-site vacancies, especially to the larger, and hence less mobile, Y 3 interstitialcies and their c-type vacant sites. The obtained data allow to resolve various charge transport mechanisms: (i) tunneling of electrons in combination with intra-atomic excitations in the low-temperature zone (4 K < T < 55 K); (ii) small-polaron hopping, extended over the range 80 K < T < 350 K; (iii) primarily radiation-induced, Debye-type ionic reorientation processes with peak temperatures near to 250, 325 and 400 K.Einkristalliner Yttrium-Eisen-Granat wurde bei T % 80 K mit 3 MeV-Elektronen auf eine Dosis von ! 10 19 e À cm À2 bestrahlt und die anschlieûende Erholung der Gitterfehler, nach systematischem Anlassen u È ber einen Temperaturbereich von 80 K < T a < 1400 K, mit Hilfe magnetischer Nachwirkungsspektroskopie im Gebiet 4 K < T < 500 K sorgfa È ltig untersucht. Der weit ausgedehnte Erholungsbereich wird, neben Fe 3 und Fe 2 Zwischengitter-Ionen und deren zugeho È riger d-und a-Platz Leerstellen, hauptsa È chlich den gro È ûeren, und damit unbeweglicheren, Y 3 ZwischengitterIonen und ihren c-Platz Leerstellen zugeordnet. Die gewonnenen Daten erlauben eine deutliche Unterscheidung folgender Ladungstransport-Vorga È nge: (i) Tunneln von Elektronen in Verbindung mit intra-atomarer Anregung (4 K < T < 55 K); (ii) Klein-Polaron-Hu È pfen im Bereich 80 K < T < 350 K; (iii) bestrahlungsinduzierte, durch Ionenspru È nge verursachte Debye-Prozesse mit Maximumtemperaturen von 250, 325 und 400 K.

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Analysis of Magnetic After-Effects in Manganese Ferrites

Cited by 7 publications

References 37 publications

The Verwey transition - a topical review

The Verwey transition - a topical review

Stress-induced relaxation mechanisms in single-crystalline titanomagnetites

Charge Transport Mechanisms in Single Crystalline Yttrium Iron Garnet as Resolved by Magnetic Relaxations

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