There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.

/pdf/spintronics-fundamentals-and-applications-2dx38n6phu.pdf

Spintronics: Fundamentals and applications

The last decade witnessed significant progress in angle-resolved photoemission spectroscopy (ARPES) and its applications. Today, ARPES experiments with 2-meV energy resolution and $0.2\ifmmode^\circ\else\textdegree\fi{}$ angular resolution are a reality even for photoemission on solids. These technological advances and the improved sample quality have enabled ARPES to emerge as a leading tool in the investigation of the high-${T}_{c}$ superconductors. This paper reviews the most recent ARPES results on the cuprate superconductors and their insulating parent and sister compounds, with the purpose of providing an updated summary of the extensive literature. The low-energy excitations are discussed with emphasis on some of the most relevant issues, such as the Fermi surface and remnant Fermi surface, the superconducting gap, the pseudogap and $d$-wave-like dispersion, evidence of electronic inhomogeneity and nanoscale phase separation, the emergence of coherent quasiparticles through the superconducting transition, and many-body effects in the one-particle spectral function due to the interaction of the charge with magnetic and/or lattice degrees of freedom. Given the dynamic nature of the field, we chose to focus mainly on reviewing the experimental data, as on the experimental side a general consensus has been reached, whereas interpretations and related theoretical models can vary significantly. The first part of the paper introduces photoemission spectroscopy in the context of strongly interacting systems, along with an update on the state-of-the-art instrumentation. The second part provides an overview of the scientific issues relevant to the investigation of the low-energy electronic structure by ARPES. The rest of the paper is devoted to the experimental results from the cuprates, and the discussion is organized along conceptual lines: normal-state electronic structure, interlayer interaction, superconducting gap, coherent superconducting peak, pseudogap, electron self-energy, and collective modes. Within each topic, ARPES data from the various copper oxides are presented.

https://arxiv.org/pdf/cond-mat/0208504.pdf

Angle-resolved photoemission studies of the cuprate superconductors

In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Large efforts have been lately devoted to the study of the structural, magnetic and transport properties of magnetic tunnel junctions (MTJ) [1] due to their potential applications as low magnetic field sensors and magnetic random access memories. MTJ are based on trilayered systems of the type FM1/I/FM2, where FMI and FM2 are ferromagnetic electrodes and I is a thin insulating barrier (1–3 nm in thickness). Much research have been undertaken on insulating barriers based on an Al layer which is oxidized either after being deposited (e.g., by natural or plasma oxidation) or while being deposited (e.g., by reactive sputtering). The technological needs for the application of MTJ are strongly dependent on the thickness and surface roughness of the Al layer, as well as on its oxidation, which has to be uniform and complete (without pinholes).

XPS Analysis of Thin Insulating Barriers in Magnetic Tunnel Junctions

We have studied the magnetoresistance of sputtered Fe/Cr superlattices as a function of 500 keV Xe+ irradiation in the fluence range of 1 × 1010 to 1 × 1015 Xe+/cm2. The results show that the giant magnetoresistance is enhanced for intermediate fluences and greatly suppressed for higher fluences. The suppression of the giant magnetoresistance is due to the destruction of the antiferromagnetic order, and the mechanism for the enhancement is under investigation.

Xe + Irradiation Increases Magnetoresistance in Sputtered Fe/Cr Superlattices

The angular dependence of the upper critical fields, H c (θ) for a set of NbTi-Ge superlattices were studied at various temperatures. The behavior of H c (θ) at lower temperatures deviates from the Tinkham expression which is expected to be valid only in the Ginzberg-Landau regime close to T c . We examine a model for calculating H c (θ) involving the lowest eigenvalue of the gauge invariant diffusion equation (subject to boundary conditions appropriate to a slab) in the de Gennes expression for the upper critical field of a dirty superconductor at all temperatures. The disorder related localization and interaction effects as well, as the paramagnetic limiting effect, are also considered.

Angular Dependent Critical Fields in NbTi-Ge Superlattices in the Weakly Localized Regime

Magnetotransport in Mo/Ni superlattices

The authors measured the critical current density Jc of artificially grown Ge/Pb multilayers as a function of the magnetic field Hperpendicular to applied perpendicular to the layers. In these layered structures Jc(Hperpendicular to ) rapidly drops to a pronounced minimum at a field H*perpendicular to , then increases through a broad maximum and finally decays to zero at Hc2 perpendicular to . The systematic evolution of this minimum as a function of temperature, layer thickness and pinning strength allows us to conclude that this peculiar behavior is due to a thermally driven softening of the flux line lattice which can be related either to a magnetic decoupling or a melting of the vortex structure.

Ivan K. Schuller

Papers

XPS Analysis of Thin Insulating Barriers in Magnetic Tunnel Junctions

Xe + Irradiation Increases Magnetoresistance in Sputtered Fe/Cr Superlattices

Angular Dependent Critical Fields in NbTi-Ge Superlattices in the Weakly Localized Regime

Magnetotransport in Mo/Ni superlattices

Softening of the flux line lattice in Ge/Pb multilayers