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Quantum thermodynamics strives to extend classical thermodynamics and nonequilibrium statistical physics to ensembles of sizes below the thermodynamic limit with the full inclusion of quantum effects. This paper uses the nonrelativistic quantum mechanics of a lone system in a thermal bath to relate its wave function's local phase to Lorentz-Faraday forces acting thereon. In the intake of heat from its surroundings, such a system's entropy increases with the gain connected to the gradient field of its local phase whose subharmonicity within the boundary of its volume is a necessary and sufficient condition for it to comply with the second law of thermodynamics (SLT). The thermodynamic arrow of time necessitates irreversible over reversible processes as determined by the gradient field of the phase. Conservative Lorentz-Faraday forces identified herein impress on the system to engender irreversible (reversible) change and entropy gain (stasis) in its exchange of heat with its environment under the discernment of the thermodynamic arrow of time and regardless of the time-reversal symmetry of such venerable frameworks as electrodynamics and quantum mechanics. Entropy production is greatest when the local phase is subharmonic within the system's nominal volume. A means of time-averaging entropy and free energy changes under nonstandard-state conditions with the accommodation of phenomenological relaxation is provided. Both the SLT and Faraday's law of induction are of similar vintage and status. Surprisingly, they share a hitherto unrecognized connection at the microscopic level. Faraday's law of induction is shown to hold for a lone system provided the gradient of its local phase is finite, a necessary and sufficient condition for it not to present with its alleged paradoxes and contradictions despite its technological successes rivalling those of the SLT. There is no evidence to deny the successes of both the SLT and Faraday's law for science and technology. In compliance with Earnshaw's theorem, the potential of the Lorentz-Faraday force is shown to stabilize a lone system just like the Coulomb (or Newtonian) potential while continuing to fulfill the virial theorem. A consequence of the time asymmetry of entropy is the impossibility of travel to the past as to cause entropy changes to decrease contrary to the SLT. Further consequences of entropy's time asymmetry include at least the nonexistence of magnetic monopoles, the observed matter-antimatter asymmetry in leptonic and baryonic matter, and the role of axion-like particles in accounting for the absence of charge-parity violations in strong interactions without necessarily answering for dark matter. Within the range of validity of gravito(electro)magnetism, dark energy is identified as the work done by the Heaviside analog of the Lorentz-Faraday force in causing the accelerated expansion of the Universe without reference to either a finite cosmological constant or an unstable vacuum state transition. In the practice of reductionism, macroscopic physics supervenes upon the microscopic, the SLT being the most conspicuous exception to that superfluous tenet. The supersedence of classical thermodynamics over quantum mechanics and electrodynamics across spatio-temporal scales ranging from an individual quantized system to its known Universe has been shown herein. Additionally, in showing that reversible (irreversible) processes are affiliated with the particle (wave) behavior of matter, attention has been drawn to a heretofore overlooked connection between the different roles of classical thermodynamics and quantum mechanics and electrodynamics in respect to arrow-of-time asymmetry and wave-particle duality., 1 Introduction 1.1 Background and purpose Charge conjugation (C), parity (P), and time (T) are the three most important discrete symmetries and hold for all physical phenomena in Nature: C [...]

A chemical kinetic model is presented for the formation and accumulation of secondary ferrimagnetic minerals (SFMs) in soil constructed using experimentally determined rate constants and validated against field data. The primary objective is to critically assess the significance of competing causal mechanisms and disputed environmental controls under temperate conditions. Four findings are important in relation to current application of soil magnetic susceptibility data. First, transformation of hydrous ferric oxide to magnetite should dominate SFM formation, controlled primarily by parent material ferrous silicate concentration and climate. Second, abiotic reactions should account for most of the SFM production; the most significant impact of high [Fe.sup.2+] concentrations created by dissimilatory iron-reducing bacteria is enhanced export of iron from the soil in runoff. Third, the model predicts a correlation between hematite and magnetite concentrations, weakening field support for direct transformation of hydrous ferric oxide to maghemite. Fourth, magnetic susceptibility enhancement should increase strongly with weathering duration. doi: 10.1130/G31514.1

Mean-field continual model of Ruderman--Kittel--Kasuya--Yosida (RKKY) magnetism in thin films and wires is considered. The spatial distribution of the magnetization is described by the nonlinear integral equation. The magnetization distribution over the film thickness or the wire diameter is close, correspondingly, to the parabolic or Gaussian one. The dependence of the Curie temperature on the film thickness, and temperature dependencies of the average film and wire magnetizations are determined. Index Terms--Magnetic films, magnetic semiconductors.

Magnetic ground states in solids often arise as a result of a delicate balance between competing factors. One currently active area of research in magnetic materials involves compounds in which long-range magnetic ordering at low temperatures is frustrated by the geometry of the crystalline lattice, a situation known as geometrical magnetic frustration. The number of systems known to display the effects of such frustration is growing, but those that are sufficiently simple from theoretical, chemical, and physical perspectives to allow for detailed understanding remain very few. A search for model compounds in this family has led us to the double perovskites [Ba.sub.2]LnSb[O.sub.6] and [Sr.sub.2]LnSb[O.sub.6] (Ln = Dy, Ho, and Gd) reported here. [Ba.sub.2]DySb[O.sub.6], [Ba.sub.2]HoSb[O.sub.6], [Sr.sub.2]DySb[O.sub.6], and [Sr.sub.2]HoSb[O.sub.6] are structurally characterized by powder neutron diffraction at ambient temperature. The trivalent lanthanides and pentavalent antimony are found to be fully ordered in the double-perovskite arrangement of alternating octahedra sharing corner oxygens. In such a structure, the lanthanide sublattice displays a classical fcc arrangement, an edge-shared network of tetrahedra known to result in geometric magnetic frustration. No magnetic ordering is observed in any of these compounds down to temperatures of 2 K, and in the case of the Dy-based compounds in particular, frustration of the magnetic ordering is clearly present. Lanthanide-based double perovskites are proposed to be excellent model systems for the detailed study of geometric magnetic frustration.

Sputtered [(Pt-Co).sub.n]-FeMn multilayers exhibit both perpendicular magnetic anisotropy and exchange bias at room temperature. Their magnetic properties after in-plane and perpendicular-to-plane magnetic annealing have been studied by means of extraordinary Hall effect and magnetic force microscopy or polar Kerr microscopy. A crossover from in-plane to perpendicular anisotropy was observed as a function of number of repeats n. The dynamics of magnetization switching has been investigated on both sides of the hysteresis loops. A clear asymmetry exists in the dynamics depending whether the field is parallel or antiparallel to the exchange bias field. Similarly, strong differences in the domain patterns at the coercive field were observed. Exchange-biased (Pt-Co)-Pt-(Pt-Co)-FeMn spin-valves were also investigated. Well-separated hysteresis loops were associated with the 'soft' and pinned components of the stack. These structures were used to study the interlayer coupling through the Pt spacer. Index Terms--Exchange bias, interlayer coupling, magnetic switching dynamics, perpendicular magnetic anisotropy.

This paper presents a method for modeling magnetoelastic material where magnetic and mechanical (elastic) phenomena are coupled in consequence of magnetic forces and magnetostriction. First, the basic equations and constitutive laws are derived on the basis of a continuum description of magnetoelastic material. Further, the numerical implementation by using the finite-element method is discussed and illustrated by means of an application example. Index Terms--Magnetic forces, magnetoelasticity, magnetostriction.

A fast differential equation approach for the Della Torre, Oti, and Kadar model has been extented to the complete moving hysteresis (CMH) model. Also, a cobweb technique for calculating the CMH model is also presented. The two techniques are contrasted from the point of view of flexibility and computation time. Index Terms--Cobweb, complete moving hysteresis model, hysteresis, magnetic modeling, Preisach model.

The time-domain performance of a number of absorbing boundary conditions invoked on the boundary of a domain of computation, as well as of a perfectly matched layer surrounding such a domain, is carried out for a test configuration for which analytic expressions for the relevant field quantities exist. The test configuration consists of a small loop antenna radiating into a homogeneous, isotropic half-space. On the planar boundary of this half-space, either an absorbing boundary condition is invoked or a perfectly matched layer is started that is truncated at some finite depth of penetration. For a loop parallel to the boundary, closed-form analytic expressions for all field components of the spuriously reflected field are presented for all truncation conditions involved. A number of important features show up that might he masked in purely numerical implementations of the procedures under consideration. Index Terms--Absorbing boundary conditions, computational modeling, perfectly matched layers.

A formalism based on the perturbation theory, which permits for an analytical approximation to the solution of the micromagnetic equations, is presented. The approximation is applicable in the limit of small deviations of the magnetization from the uniformly magnetized state. These small deviations can lead to large effective anisotropy fields in magnetic elements, which can be large enough to dominate the spin reversal behavior.

An analytical approach is developed to predict the inverter high frequency pulse width modulation (PWM) switching caused eddy-current losses in a permanent magnet brushless dc motor. The model uses polar coordinates to take curvature effects into account, and is also capable of including the space harmonic effect of the stator magnetic field and the stator lamination effect on the losses. The model was applied to an existing motor design and was verified with the finite element method. Good agreement was achieved between the two approaches. Hence, the model is expected to be very helpful in predicting PWM switching losses in permanent magnet machine design. Index Terms - Eddy-current loss, permanent magnet brushless dc motors, pulse width modulation switching, space harmonics.

The crossover of the hysteresis branches in the classical coherent rotation model is analyzed. The analysis is extended when the truncated Stoner-Wohlfarth astroid is used. The physical explanation of the crossover occurrence is given. More accurate expressions of the anisotropy free energy density are required to better describe the behavior of the system when the angle between the easy axis and the magnetic moment of the particle is near 90[degrees]. A simple approximate formula for the hysteresis loop branches, which are in good agreement with those obtained when the discussed corrections are made, is given. The effect of the use of the Stoner-Wohlfarth astroid in the calculus of the equilibrium state in some vector Preisach-type models is analyzed. Index Terms - Magnetic anisotropy, micromagnetics, particulate recording media, Preisach model, Stoner-Wohlfarth model.

Monte Carlo simulations are conducted to analyze the magnetic relaxation of a small particle system with dipolar interaction. The simulation system is a simplified version of the real situation in a small particle system with random distribution of anisotropy axes and long range dipolar interaction among the particles. The model is composed of a one-dimensional Ising model with dipolar interaction and a distribution of uniaxial anisotropy strengths. The anisotropy axes are considered perpendicular to the line connecting the spins.

An optical fiber imaging system helps evaluate the influences of magnetic and gas dynamics on the arc chamber of miniature circuit breakers. A one-dimensional flow model, based on magnetic calculations, enables the analysis of these influences. Magnetic data, in conjunction with conductivity and pressure data, indicate factors affecting the arc chamber environment such as steel, plasma jet and formation of pressure waves.

We present a new finite element method in micromagnetics. The magnetization is linearly interpolated within each tetrahedral element and the magnetostatic interaction is accurately obtained by integration. The equilibrium magnetizations at the nodal points can be found by minimizing the total energy of the system. Two different minimization schemes are compared.

The physical structure of the magnetic electrodes of Co-[Al.sub.2][O.sub.3]-Co magnetic tunnel junctions has been investigated by means of [sup.59]Co nuclear magnetic resonance and X-ray diffraction. Junctions sputtered on FeMn have an essentially fcc (111)-oriented bottom electrode, while all top electrodes and the bottom electrodes of junctions sputtered on Ta are polyphase and polycrystalline. The specifics of the electronic structure of the electrode crystal phases can explain the extra features and asymmetry in the conductance-versus-bias behavior observed in FeMn-based junctions. Index Terms--Electronic structure, magnetic tunnel junctions, NMR, structural analysis.

The normal modes of an inhomogeneons thin film are obtained by diagonalization of the perturbed Hamiltonian. The resulting modes are mixtures of the spin-wave modes and the uniform mode. We find that the ferromagnetic resonance intensity spectrum of the diagonalized system has a Lorentzian profile, and that the results correspond to the two-magnon model for weak perturbations. For stronger perturbations, the density of states is smoothed, and the spectrum becomes asymmetric due to the low-frequency cutoff of the spin-wave manifold. The technique is expected to be valid for perturbation amplitudes that are large enough to invalidate the assumptions of the two-magnon model. Index Terms--Damping, ferromagnetic resonance, magnetic thin films, two-magnon model.

This paper presents a way to relate two standard models for magnetomechanical hysteresis - the Sablik-Jiles-Atherton model and the Schneider-Cannell-Watts model - while at the same time presenting physical models for the asymmetry in magnetic property behavior under tensile and compressive stress in steel, including, for oH processes, the presence of an extremum in the dependence of magnetic properties on tensile stress, an effect which is sometimes known as the Villari effect.

Simulations of magnetic and magnetoelastic behavior based on micromagnetic theory exhibit hysteresis. These magnetic systems have a highly nonlinear character involving short and long range fields. Computational results are presented and the role of various energetic contributions assessed and predicted using methods of contemporary nonlinear analysis.

A series of experiments that aim to explore interactions between magnets, ferromagnetic materials, and current-carrying wires is described. These experiments will help students develop a model of magnetism that explains these interactions.

A ferromagnetic, planar spin-model with random anisotropies in two dimensions is used to simulate thermally activated processes in exchange-coupled, two-phase permanent magnets by Monte Carlo dynamics. Simulations of hysteresis and slow relaxation processes at finite temperature are reported. The model displays exchange-spring behavior, anomalous viscosity along recoil loops, and thermal remagnetization in qualitative accord with experimental findings on spring magnets. The anomalous relaxation of the model can be explained by shrinking of subcritical interaction domains along the recoils. It is argued that disorder is important for the observability of anomalous viscosity in materials, which undergo magnetic reversal by nucleation and growth of interaction domains. Index Terms--Magnetization processes and modeling, viscosity, spring magnets, thermal remagnetization.

Author(s): Christian Roos (corresponding author) [1] Studies of the oscillation of vibrating plates date back centuries. In the eighteenth century, the German physicist Ernst Chladni used small amounts of sand [...]

A simple proof of the vanishing of magnetic flux over a closed surface, based on elementary vector algebra and symmetry considerations, is presented. 2002 American Association of Physics Teachers.