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Photelectron spectroscopy of ultra-thin epitaxial f.c.c. magnetic films of iron and cobaltAmiri-Hezaveh, A. January 1987 (has links)
No description available.
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Magnetotransport in magnetic multilayers : a study of FeNi/Cu/Co trilayersPatel, Merul January 1994 (has links)
No description available.
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Atomic-Scale Interface Magnetism for SpintronicsLaloë, Jean-Baptiste 23 May 2007 (has links) (PDF)
Recognising that the characterisation of actual interfaces in magnetic multilayer systems will provide valuable insight for the integration of spintronics in practical devices, a study of interface effects in various structures is presented. Magnetometry measurements are performed for a range of Fe thicknesses (0.4 - 23 nm) grown by molecular beam epitaxy on GaAs and InAs substrates in order to determine the factors governing the evolution of the magnetic moment of epitaxial Fe grown on a zinc-blende semiconductor. A greater reduction of the Fe magnetic moment is observed for films grown on InAs as compared to GaAs, as the Fe films reach a bulk-like moment (within 10% deviation) at a thickness of ~5.2 nm and ~2.2 nm, respectively. From this direct comparative study it is concluded that interface and interdiffusion effects are the dominant mechanisms influencing the value of the magnetic moment for ultra-thin Fe films on GaAs and InAs. Spin injection at this interface is performed, by detecting optical polarisation in the oblique Hanle geometry from a Fe/AlGaAs/GaAs spin-light emitting diode structure. The electrical and magnetic properties of the system are presented, and a ~1% injection polarisation at room temperature, rising to ~4% at 77 K is reported. A study of the deposition and growth of MgO thin (3 - 39 nm) films in conjunction with magnetic layers is also performed. Crystallinity of MgO grown on GaAs is obtained, and epitaxial growth of Fe and Co on MgO is demonstrated. Polarised neutron reflectivity results again indicate a slight decrease in Fe and Co magnetic moments due to interfacial oxide layers. MgO is also incorporated in a pseudo-spin-valve structure which demonstrates epitaxy-induced magneto-crystalline anisotropy. It is concluded that the interface quality is a critical parameter for spintronic devices. Atomic-scale defects and intermixing in real samples mean that current theoretical estimates of ~100% injection efficiency in perfect systems remain unattainable. However by increasing atomic-level structural control of interfaces, a substantial increase in efficiency might be achieved, similarly to the recent breakthrough in tunnelling magneto-resistance ratios which have reached 1000%.
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Theoretical Investigations of Skyrmions in Chiral MagnetsRowland, James R., IV January 2019 (has links)
No description available.
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Ferromagnetic thin films of Fe and Fe 3 Si on low-symmetric GaAs(113)A substratesMuduli, Pranaba Kishor 24 April 2006 (has links)
In dieser Arbeit werden das Wachstum mittels Molekularstrahlepitaxie und die Eigenschaften der Ferromagneten Fe und Fe_3Si auf niedrig-symmetirschen GaAs(113)A-Substraten studiert. Drei wichtige Aspekte werden untersucht: (i) Wachstum und strukturelle Charakterisierung, (ii) magnetische Eigenschaften und (iii) Magnetotransporteigenschaften der Fe und Fe_3Si Schichten auf GaAs(113)A-Substraten. Das Wachstum der Fe- und Fe_3Si-Schichten wurde bei einer Wachstumstemperatur von = bzw. 250 °C optimiert. Bei diesen Wachstumstemperaturen zeigen die Schichten eine hohe Kristallperfektion und glatte Grenz- und Oberflächen analog zu [001]-orientierten Schichten. Weiterhin wurde die Stabilität der Fe_(3+x)Si_(1-x) Phase über einen weiten Kompositionsbereich innerhalb der Fe_3Si-Stoichiometry demonstriert. Die Abhängigkeit der magnetischen Anisotropie innerhalb der Schichtebene von der Schichtdicke weist zwei Bereiche auf: einen Beresich mit dominanter uniaxialer Anisotropie für Fe-Schichten = 70 MLs. Weiterhin wird eine magnetische Anisotropie senkrecht zur Schichtebene in sehr dünnen Schichten gefunden. Der Grenzflächenbeitrag sowohl der uniaxialen als auch der senkrechten Anisotropiekonstanten, die aus der Dickenabhängigkeit bestimmt wurden, sind unabhängig von der [113]-Orientierung und eine inhärente Eigenschaft der Fe/GaAs-Grenzfläche. Die anisotrope Bindungskonfiguration zwischen den Fe und den As- oder Ga-Atomen an der Grenzfläche wird als Ursache für die uniaxiale magnetische Anisotropie betrachtet. Die magnetische Anisotropie der Fe_3Si-Schichten auf GaAs(113)A-Substraten zeigt ein komplexe Abhängigkeit von der Wachstumsbedingungen und der Komposition der Schichten. In den Magnetotransportuntersuchungen tritt sowohl in Fe(113)- als auch in Fe_3Si(113)-Schichten eine antisymmetrische Komponente (ASC) im planaren Hall-Effekt (PHE) auf. Ein phänomenologisches Modell, dass auf der Kristallsymmetrie basiert, liefert ein gute Beschreibung sowohl der ASC im PHE als auch des symmetrischen, anisotropen Magnetowiderstandes. Das Modell zeigt, dass die beobachtete ASC als Hall-Effekt zweiter Ordnung beschreiben werden kann. / In this work, the molecular-beam epitaxial growth and properties of ferromagnets, namely Fe and Fe_3Si are studied on low-symmetric GaAs(113)A substrates. Three important aspects are investigated: (i) growth and structural characterization, (ii) magnetic properties, and (iii) magnetotransport properties of Fe and Fe_3Si films on GaAs(113)A substrates. The growth of Fe and Fe_3Si films is optimized at growth temperatures of 0 and 250 degree Celsius, respectively, where the layers exhibit high crystal quality and a smooth interface/surface similar to the [001]-oriented films. The stability of Fe_(3+x)Si_(1-x) phase over a range of composition around the Fe_3Si stoichiometry is also demonstrated. The evolution of the in-plane magnetic anisotropy with film thickness exhibits two regions: a uniaxial magnetic anisotropy (UMA) for Fe film thicknesses = 70 MLs. The existence of an out-of-plane perpendicular magnetic anisotropy is also detected in ultrathin Fe films. The interfacial contribution of both the uniaxial and the perpendicular anisotropy constants, derived from the thickness-dependent study, are found to be independent of the [113] orientation and are hence an inherent property of the Fe/GaAs interface. The origin of the UMA is attributed to anisotropic bonding between Fe and As or Ga at the interface, similarly to Fe/GaAs(001). The magnetic anisotropy in Fe_3Si on GaAs(113)A exhibits a complex dependence on the growth conditions and composition. Magnetotransport measurements of both Fe(113) and Fe_3Si(113) films shows the striking appearance of an antisymmetric component (ASC) in the planar Hall effect (PHE). A phenomenological model based on the symmetry of the crystal provides a good explanation to both the ASC in the PHE as well as the symmetric anisotropic magnetoresistance. The model shows that the observed ASC component can be ascribed to a second-order Hall effect.
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