Magnetic and Transport Properties of Colossal Magnetoresistance Manganites and Magnetic Semiconductors

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dc.contributor.authorWanjun, Jiang
dc.contributor.examiningcommitteeCoey, J. M. D. (Physics, Trinity College, Dublin) Hu, C. M. (Physics and Astronomy) Roshko, R. (Physics and Astronomy) Richards, N. (Mechanical & Manufacturing Engineering)en
dc.contributor.supervisorWilliams, Gwyn (Physics and Astronomy)en
dc.date.accessioned2010-05-12T16:39:51Z
dc.date.available2010-05-12T16:39:51Z
dc.date.issued2010-05-12T16:39:51Z
dc.degree.disciplinePhysics and Astronomyen_US
dc.degree.levelDoctor of Philosophy (Ph.D.)en_US
dc.description.abstractTransition metal and related compounds have been extensively studied over the past several decades. These investigations revealed a wide range of behavior, encompassing colossal magnetoresistance (CMR), high-TC superconductivity, and magnetic semiconductivity, all of which continue to present fundamental challenges to the understanding of such phenomena. There is, however, a close correlation between such characteristics and the appearance of magnetic order. This correlation underlies the present study, which focuses on the magnetic and transport behavior of various Manganese (Mn), Iron (Fe) and Cobalt (Co) containing materials, with particular emphasis on the nature of the magnetic order they display and the critical exponents that characterize the accompanying phase transition. The magnetic and transport properties of two specific systems will be covered: first various doped manganites from the series (La,Pr)1-x(Ca,Ba)xMnO3, and second the magnetic semiconductors Fe0.8Co0.2Si and Ga0.98Mn0.02As. In the manganites, the influence of doping on; (i) the evolution of the metal-insulator transition (MIT) with composition; (ii) the universality class of the magnetic critical behavior associated with the paramagnetic to ferromagnetic transition, which occurs in the vicinity of a MIT with which CMR is associated; (iii) the mechanisms underlying ferromagnetism across the MIT; (iv) the correlation between the appearance of a Griffiths-like phase and CMR, and (v) the origin of Griffiths-like phase have been investigated. Four different systems have been studied: La1-xCaxMnO3 (0.18 ≤ x ≤ 0.27), La1-xBaxMnO3 (x ≤ 0.33), (La1-yPry)0.7Ca0.3Mn16/18O3 (y ≤ 0.85), and Pr1-xCaxMnO3 (x = 0.27, 0.29). In Fe0.8Co0.2Si and Ga0.98Mn0.02As, the scaling between magnetization and conductivity has been the subject of ongoing debate. In bulk Fe0.8Co0.2Si, a novel scaling between the anomalous Hall effect (AHE) and the magnetization enables the anomalous Hall coefficient to be accurately determined. In turn, this enables the universality class for the transition to ferromagnetism to be established independently from the anomalous Hall conductivity. In an epitaxial (metallic) Ga0.98Mn0.02As microstructure, the magnetization has been indirectly determined from the AHE. Subsequent analysis yields magnetic critical exponents consistent with the Mean-Field model, direct support for which had previously been lacking.en
dc.description.noteOctober 2010en
dc.format.extent18321383 bytes
dc.format.mimetypeapplication/pdf
dc.identifier.citationWanjun Jiang, Xuezhi Zhou, Gwyn Williams, Y. M. Mukovskii, and K. Glazyrin. Physical Review Letters, 99, 177203 (2007).en
dc.identifier.citationWanjun Jiang, Xuezhi Zhou, Gwyn Williams, Y. M. Mukovskii, and K. Glazyrin. Physical Review B, 76, 092404 (2007).en
dc.identifier.citationWanjun Jiang, Xuezhi Zhou, Gwyn Williams, Y. M. Mukovskii, and K. Glazyrin. Physical Review B, 77, 064424 (2008).en
dc.identifier.citationWanjun Jiang, Xuezhi Zhou, Gwyn Williams, Y. M. Mukovskii, and K. Glazyrin. Physical Review B, 78, 144409 (2008).en
dc.identifier.citationWanjun Jiang, Xuezhi Zhou, Gwyn Williams. Europhysics Letters, 84, 47009 (2008).en
dc.identifier.citationWanjun Jiang, André Wirthmann, Y. S. Gui, X. Z. Zhou, M. Reinwald, W. Wegscheider, C.-M. Hu, and Gwyn Williams. Physical Review B, 80, 214409 (2009).en
dc.identifier.citationWanjun Jiang, Xuezhi Zhou, Gwyn Williams, Y. Mukovskii, and R. Privezentsev. Physical Review B, 79, 214433 (2009).en
dc.identifier.citationWanjun Jiang, Xuezhi Zhou, Gwyn Williams, Y. Mukovskii, and R. Privezentsev. Journal of Physics: Condensed Matter, 21, 415603 (2009).en
dc.identifier.citationWanjun Jiang, Xuezhi Zhou, Gwyn Williams, Y. Mukovskii, and R. Privezentsev. Journal of Physics: Conference Series, 200, 012072 (2010).en
dc.identifier.urihttp://hdl.handle.net/1993/3987
dc.language.isoengen_US
dc.rightsopen accessen_US
dc.subjectMagnetismen
dc.subjectColossal Magnetoresistance Manganitesen
dc.subjectDiluted Magnetic Semiconductorsen
dc.subjectMagnetic Critical Phenomenaen
dc.subjectMetal-Insulator Transitionen
dc.subjectAnomalous Hall Effecten
dc.subjectPhase Separationen
dc.subjectGriffiths-like Phaseen
dc.titleMagnetic and Transport Properties of Colossal Magnetoresistance Manganites and Magnetic Semiconductorsen
dc.typedoctoral thesisen_US
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