Magnetism

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David J. Dunlop - One of the best experts on this subject based on the ideXlab platform.

  • Rock Magnetism: Fundamentals and Frontiers
    1997
    Co-Authors: David J. Dunlop, Özden Özdemir
    Abstract:

    Preface 1. Magnetism in nature 2. Fundamentals of Magnetism 3. Terrestrial magnetic materials 4. Magnetostatic fields and energies 5. Elementary domain structure and hysteresis 6. Domain observations 7. Micromagnetic calculations 8. Single-domain thermoremanent magnetization 9. Multidomain thermoremanent magnetization 10. Viscous and thermoviscous magnetization 11. Isothermal magnetization and demagnetization 12. Pseudo-single-domain remanence 13. Crystallization remanent magnetization 14. Magnetism of igneous rocks and baked materials 15. Magnetism of sediments and sedimentary rocks 16. Magnetism of metamorphic rocks 17. Magnetism of extraterrestrial rocks References.

  • Rock Magnetism: Magnetism in nature
    Rock Magnetism, 1997
    Co-Authors: David J. Dunlop, Özden Özdemir
    Abstract:

    Magnetism has fascinated mankind since the invention of compasses that could track invisible magnetic field lines over the earth's surface. Much later came the discovery that rocks can fossilize a record of ancient magnetic fields. Unravelling this record – the ‘archeology’ of Magnetism – is the science of paleoMagnetism, and understanding how the microscopic fossil ‘compasses’ in rocks behave has come to be known as rock Magnetism. Rock Magnetism is both a basic and an applied science. Its fundamentals concern ferroMagnetism and magnetic domains and were developed most authoritatively by Neel. Its applications continue to expand, giving impetus to new research into the mechanisms and fidelity of rock magnetic recording. Some of the history and applications are described in this chapter. A brief history Earth Magnetism Compasses were used in China and the Arab world for centuries before Petrus Peregrinus in 1269 gave the first European description of a working compass. The earliest compasses were lodestones, naturally occurring ores of magnetite (Fe 3 O 4 ). Particular areas, or poles, of one lodestone would attract or repel the poles of another lodestone. This magnetic polarization is the key to their use as compasses in navigation. A suspended lodestone will rotate until its axis of magnetization or polarization, joining north and south poles of the lodestone, lines up with imaginary field lines joining the north and south geomagnetic poles. In modern terminology, the magnetization M aligns with the field H .

  • Magnetism in rocks
    Journal of Geophysical Research, 1995
    Co-Authors: David J. Dunlop
    Abstract:

    Rock Magnetism is the study of induced and remanent magnetization of ferrimagnetic mineral grains in rocks, sediments, soils, and organisms. Its applications include environmental Magnetism, magnetic anisotropy, sources of continental and oceanic magnetic anomalies, records of geomagnetic field variations and polarity reversals, and the paleomagnetic record of plate motions and the Wilson cycle. This paper reviews the beginnings of rock Magnetism and then traces the development of six particularly interesting areas : pseudo-single-domain behavior ; magnetic domains and micromagnetic structures ; diagnostic tests of the type and stability of remanent magnetization ; magnetic microanalysis ; thermoviscous remagnetization ; and chemical remanent magnetization. Other areas, including sediment and soil Magnetism, are covered in a companion paper by Verosub and Roberts on environmental Magnetism.

Kohji Nakamura - One of the best experts on this subject based on the ideXlab platform.

  • Computational quantum Magnetism: Role of noncollinear Magnetism
    Journal of Magnetism and Magnetic Materials, 2009
    Co-Authors: Arthur J Freeman, Kohji Nakamura
    Abstract:

    Abstract We are witnessing today a golden age of innovation with novel magnetic materials and with discoveries important for both basic science and device applications. Computation and simulation have played a key role in the dramatic advances of the past and those we are witnessing today. A goal-driving computational science—simulations of every-increasing complexity of more and more realistic models has been brought into greater focus with greater computing power to run sophisticated and powerful software codes like our highly precise full-potential linearized augmented plane wave (FLAPW) method. Indeed, significant progress has been achieved from advanced first-principles FLAPW calculations for the predictions of surface/interface Magnetism. One recently resolved challenging issue is the role of noncollinear Magnetism (NCM) that arises not only through the SOC, but also from the breaking of symmetry at surfaces and interfaces. For this, we will further review some specific advances we are witnessing today, including complex magnetic phenomena from noncollinear Magnetism with no shape approximation for the magnetization (perpendicular MCA in transition-metal overlayers and superlattices; unidirectional anisotropy and exchange bias in FM and AFM bilayers; constricted domain walls important in quantum spin interfaces; and curling magnetic nano-scale dots as new candidates for non-volatile memory applications) and most recently providing new predictions and understanding of Magnetism in novel materials such as magnetic semiconductors and multi-ferroic systems.

David J Singh - One of the best experts on this subject based on the ideXlab platform.

  • Superconductivity and Magnetism in YFe2Ge2
    Physical Review B, 2014
    Co-Authors: David J Singh
    Abstract:

    We report calculations of the electronic structure and magnetic properties of YFe${}_{2}$Ge${}_{2}$ and discuss the results in terms of the observed superconductivity near Magnetism. We find that YFe${}_{2}$Ge${}_{2}$ is a material near a magnetic quantum critical point based on comparison of standard density functional results that predict Magnetism with experiment. The band structure and Fermi surfaces are very three dimensional and higher conductivity is predicted in the $c$-axis direction. The Magnetism is of Stoner type and is predominately from an in-plane ferromagnetic tendency. The interlayer coupling is weak giving a perhaps two dimensional character to the Magnetism, which is in contrast to the conductivity and may be important for suppressing the ordering tendency. This is compatible with a triplet superconducting state mediated by spin fluctuations.

  • electronic structure and Magnetism of complex materials
    2003
    Co-Authors: David J Singh, D A Papaconstantopoulos
    Abstract:

    1 Low-Lying Magnetic Excitations in Itinerant Systems: SDFT Calculations.- 2 Calculation of Magneto-crystalline Anisotropy in Transition Metals.- 3 Electronic Structure and Magnetism of Correlated Systems: Beyond LDA.- 4 FerroMagnetism in (III,Mn)V Semiconductors.- 5 Noncollinear Magnetism in Systems with Relativistic Interactions.- 6 Orbital Degeneracy and Magnetism of Perovskite Manganese Oxides.- 7 Magnetism in Ruthenates.

Arthur J Freeman - One of the best experts on this subject based on the ideXlab platform.

  • Computational quantum Magnetism: Role of noncollinear Magnetism
    Journal of Magnetism and Magnetic Materials, 2009
    Co-Authors: Arthur J Freeman, Kohji Nakamura
    Abstract:

    Abstract We are witnessing today a golden age of innovation with novel magnetic materials and with discoveries important for both basic science and device applications. Computation and simulation have played a key role in the dramatic advances of the past and those we are witnessing today. A goal-driving computational science—simulations of every-increasing complexity of more and more realistic models has been brought into greater focus with greater computing power to run sophisticated and powerful software codes like our highly precise full-potential linearized augmented plane wave (FLAPW) method. Indeed, significant progress has been achieved from advanced first-principles FLAPW calculations for the predictions of surface/interface Magnetism. One recently resolved challenging issue is the role of noncollinear Magnetism (NCM) that arises not only through the SOC, but also from the breaking of symmetry at surfaces and interfaces. For this, we will further review some specific advances we are witnessing today, including complex magnetic phenomena from noncollinear Magnetism with no shape approximation for the magnetization (perpendicular MCA in transition-metal overlayers and superlattices; unidirectional anisotropy and exchange bias in FM and AFM bilayers; constricted domain walls important in quantum spin interfaces; and curling magnetic nano-scale dots as new candidates for non-volatile memory applications) and most recently providing new predictions and understanding of Magnetism in novel materials such as magnetic semiconductors and multi-ferroic systems.

Ismail Zahed - One of the best experts on this subject based on the ideXlab platform.

  • Chiral Disorder and Random Matrix Theory with Magnetism
    Acta Physica Polonica B, 2016
    Co-Authors: Maciej A. Nowak, Mariusz Sadzikowski, Ismail Zahed
    Abstract:

    jeHj. Weak Magnetism corresponds to jeHj 1= 2 with 1=3 fm the vacuum instanton size, while strong Magnetism the reverse. Asymptotics (ultra-strong Magnetism) is in the realm of perturbative QCD. We analyze weak Magnetism using the concept of the quark return probability in the diusive regime of chiral disorder. The result is in agreement with expectations from chiral perturbation theory. We analyze strong and ultra-strong Magnetism in the ergodic regime using random matrix theory including the eects of nite temperature. The strong Magnetism results are in agreement with the currently reported lattice data in the presence of a small shift of the Polyakov line. The ultra-strong Magnetism results are consistent with expectations from perturbative QCD. We suggest a chiral random matrix eective action with matter and Magnetism to analyze the QCD phase diagram near the critical points under the inuence of Magnetism.

  • Chiral Disorder and Random Matrix Theory with Magnetism
    arXiv: High Energy Physics - Phenomenology, 2013
    Co-Authors: Maciej A. Nowak, Mariusz Sadzikowski, Ismail Zahed
    Abstract:

    We revisit the concept of chiral disorder in QCD in the presence of a QED magnetic field |eH|. Weak Magnetism corresponds to |eH| < 1/rho^2 with rho\approx (1/3) fm the vacuum instanton size, while strong Magnetism the reverse. Asymptotics (ultra-strong Magnetism) is in the realm of perturbative QCD. We analyze weak Magnetism using the concept of the quark return probability in the diffusive regime of chiral disorder. The result is in agreement with expectations from chiral perturbation theory. We analyze strong and ultra-strong Magnetism in the ergodic regime using random matrix theory including the effects of finite temperature. The strong Magnetism results are in agreement with the currently reported lattice data in the presence of a small shift of the Polyakov line. The ultra-strong Magnetism results are consistent with expectations from perturbative QCD. We suggest a chiral random matrix effective action with matter and Magnetism to analyze the QCD phase diagram near the critical points under the influence of Magnetism.