scholarly journals The Faraday effect in ferromagnetics

1932 ◽  
Vol 135 (826) ◽  
pp. 237-257 ◽  
Keyword(s):  
Faraday Effect ◽  
Wave Length ◽  
Closed Shell ◽  
Free Electrons ◽  
Unit Distance ◽  
Rough Model ◽  
Absorption Of Light ◽  
Order Of Magnitude ◽  
Bound Electrons ◽  
London Model

1. Introduction .—If plane polarised light be transmitted through a medium under the influence of a magnetic field parallel to the direction of propagation, the plane of polarisation is in general rotated. This circumstance is known as the Faraday effect, after its discoverer. For light of a given wave-length, the magnitude of the rotation per unit distance is found to be proportional to the magnetisation. The direction of rotation varies with different substances, being termed diamagnetic, or positive, if in the direction of the current producing the field, and paramagnetic, or negative, if in the opposite sense. The sign of the effect does not depend upon whether the substance is dia- or paramagnetic; negative diamagnetics are, however, infrequent. Thin films of ferromagnetics exhibit an enormous negative rotation, proportional to the magnetisation, and in the following we shall attempt to explain the origin of this by using a very simple model for the substance. We shall consider a single crystal of the metal, and, following Heisenberg, we shall choose the Heitler-London model, where each electron is considered as being attached to an atom, as a first approximation. The interaction of the electrons gives rise to the well-known exchange forces. In a ferromagnetic these exchange forces are of vital importance, and it is therefore necessary to consider states and transitions of the crystal as a whole. Further, it is well known that in a ferromagnetic the average orbital angular momentum is zero. In view of this fact, and in the interest of simplicity, we shall consider a model where each atom possesses one electron in an s -state, outside a closed shell. This, of course, does not correspond to the facts, but any other model would be very much more difficult to handle. Having chosen a model with bound electrons, we shall have no conduction (without including polar states), and shall therefore not have the typical metallic absorption of light, such as is associated with “free” electrons. With the extremely rough model used, it is obvious that we can only expect to obtain the order of magnitude of the rotation, and some idea of its variation with the intensity of magnetisation.

Surface Plasmon Polaritons and Inverse Faraday Effect

2012 ◽  
Vol 190 ◽  
pp. 369-372 ◽  
Author(s):  
N.E. Khokhlov ◽  
V.I. Belotelov ◽  
A.N. Kalish ◽  
A.K. Zvezdin
Keyword(s):  
Surface Plasmon ◽  
Surface Plasmon Polaritons ◽  
Surface Plasmon Polariton ◽  
Faraday Effect ◽  
Angle Of Incidence ◽  
Local Magnetization ◽  
Inverse Faraday Effect ◽  
Order Of Magnitude ◽  
Plasmon Polariton ◽  
Plasmon Polaritons

t is shown that the inverse Faraday effect appears in the case of surface plasmon polariton propagation near a metal-paramagnetic interface. The inverse Faraday effect in nanostructured periodically perforated metaldielectric films increases because of the excitation of surface plasmon polaritons. In this case, a stationary magnetic field is amplified by more than an order of magnitude compared to the case of a smooth paramagnetic film. The distribution of an electromagnetic field is sensitive to the wavelength and the angle of incidence of light, which allows one to efficiently control the local magnetization arising due to the inverse Faraday effect.

Interpretation of Electron Transfer Spectra of Iridium (IV) and Osmium(IV) Mixed Chloro-Bromo Complexes

1967 ◽  
Vol 22 (6) ◽  
pp. 945-954 ◽  
Author(s):  
Chr. Klixbüll Jørgensen ◽  
W. Preetz
Keyword(s):  
Electron Transfer ◽  
Faraday Effect ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
University Of Virginia ◽  
First Order ◽  
Order Of Magnitude ◽  
Moderate Difference ◽  
The University ◽  
As If

The previous M.O. treatment of unsubstituted hexahalides has been modified, taking the results on Faraday effect obtained at the University of Virginia into account. The absorption spectra previously measured of the complexes (M=Os, Ir) trans-MCl4Br2— and trans-MCl2 Br4— are interpreted by a M.O. treatment for the symmetry D4h as electron transfer transitions, including a first-order relativistic (spin-orbit coupling) correction. The concept of holohedrized symmetry is sufficiently valid to allow a description of MCl5Br— and MClBr5— as if they were tetragonal with centre of inversion and ƒac-(or cis-)MCl3Br3— as if they were cubic. It is shown that the ligand-ligand antibonding effects have the same order of magnitude as the moderate difference in optical electronegativity between Cl- and Br-.

scholarly journals On the absorption of light by crystals

1938 ◽  
Vol 167 (930) ◽  
pp. 384-391 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Wave Length ◽  
Short Wave ◽  
Point Of View ◽  
Theoretical Point ◽  
Lattice Vibrations ◽  
Short Wave Length ◽  
Continuous Absorption ◽  
Absorption Of Light ◽  
Positive Hole

The purpose of this paper is to discuss the absorption of light by non-metallic solids, and in particular the mechanism by which the energy of the light absorbed is converted into heat. If one considers from the theoretical point of view the absorption spectrum of an insulation crystal, one finds that it consists of a series of sharp lines leading up to a series limit, to the short wave-length side of which true continuous absorption sets in (Peierls 1932; Mott 1938). In practice the lattice vibrations will broaden the lines to a greater of less extent. When a quantum of radiation is absorbed in the region of true continuous absorption, a free electron in the conduction band and a "positive hole" are formed with enough energy to move away from one another and to take part in a photocurrent within the crystal. When, however, a quantum is absorbed in one of the absorption lines , the positive hole and electron formed do not have enough energy to separate, but move in one another's field in a quantized state. An electron in a crystal moving in the field of a positive hole has been termed by Frenkel (1936) an "exciton".

scholarly journals A new method of spectrophotometry in the visible and ultra­violet and the absorption of light by silver bromide

1920 ◽  
Vol 97 (683) ◽  
pp. 181-190 ◽  
Keyword(s):  
Light Intensity ◽  
Photographic Plate ◽  
Wave Length ◽  
New Method ◽  
Silver Bromide ◽  
Selective Absorption ◽  
Quantitative Investigation ◽  
Advantages And Disadvantages ◽  
Absorption Of Light

A quantitative investigation of the absorption of light by silver bromide has been undertaken as a preliminary to a photochemical investigation of the action of silver bromide in the photographic dry plate. A good summary of the advantages and disadvantages of the various methods which have been devised by different experimenters for the quantitative investigation of the absorption of light by substances is given by Ewest in a thesis entitled, “Beiträge zur quantitativen Spectralphotographie,” of which an abstract is given by F. F. Renwick. All the methods which have been used previously either depend upon Schwarzschild’s law of the relation between time of exposure and the photographic effect, or a so-called neutral wedge is used which is supposed to absorb equally in all wave-lengths or is calibrated for selective absorption. The method which we have used is in some ways similar to that used by Ewest, but the apparatus required is very much simpler and a wedge of the material under examination is used instead of the neutral wedge of Ewest. In our method all that is required of the photographic plate is that the exposure of two adjacent portions of the same plate to the same light intensity of the same wave-length or the same time gives the same density under identical conditions of development. This condition is easily satisfied. As will be seen in the sequel, errors are reduced to errors in measurements of length.

The continuous absorption of light in alkali-metal vapours

1953 ◽  
Vol 219 (1136) ◽  
pp. 89-101 ◽  
Keyword(s):  
Cross Section ◽  
Alkali Metals ◽  
Theoretical Calculations ◽  
Wave Length ◽  
Energy Difference ◽  
Continuous Absorption ◽  
Absorption Of Light ◽  
Sodium Vapour ◽  
Good Agreement ◽  
Dipole Length

The first section of this paper is an account of some experiments on the absorption of light in sodium vapour from the series limit at 2412 Å to about 1600 Å (an energy difference of 2·6 eV). The absorption cross-section at the limit is 11·6 ± 1·2 x 10 -20 cm 2 . The cross-section decreases giving a minimum of 1·3 ± 0·6 x 10 -20 cm 2 at 1900 Å and then increases to 1600 Å. A theoretical calculation by Seaton based on the dipole-length formula gives good agreement with the experiments at the series limit and also correctly predicts the wave-length for the minimum, but it predicts a significantly lower absorption at the minimum. The experiments described in the first section of the paper conclude a series on the absorption of light in the alkali metals. The second section consists of a general discussion of the results of these experiments and of their relation to theoretical calculations. There is good agreement between theory and experiment except in regard to the magnitude of the absorption at the minimum.

XIV.—The Absorption of Light by Inorganic Salts. No. XI.: Conclusion

1914 ◽  
Vol 33 ◽  
pp. 156-165
Author(s):  
R. A. Houstoun
Keyword(s):  
Special Reference ◽  
Present State ◽  
Light Wave ◽  
Wave Length ◽  
The Body ◽  
Inorganic Salts ◽  
Short Account ◽  
Absorption Of Light ◽  
Dispersion Of Light

In this paper a short account will be given of the present state of the theory of the absorption of light, with special reference to the results gained in this series of investigations.Theories of the dispersion of light may be divided into two classes: (1) those in which the body is regarded as consisting of particles which vibrate under the influence of the light wave; and (2) those in which the body is regarded as consisting of obstacles which diffract the light wave. According to (2), light is scattered, not absorbed; a wave going through the body diminishes in intensity, but the energy lost is radiated out laterally without change of wave-length.

THE THEORY OF OPTICAL ABSORPTION IN ALKALI METAL CRYSTALS

1934 ◽  
Vol 10 (3) ◽  
pp. 335-341
Author(s):  
W. H. Watson
Keyword(s):  
Absorption Band ◽  
Optical Absorption ◽  
Alkali Metal ◽  
Lattice Constant ◽  
Wave Length ◽  
Ultra Violet ◽  
Periodic Lattice ◽  
Free Electrons ◽  
Sodium Potassium ◽  
Upper Limit

The experimental results of R. W. Wood are compared with theory using the model of free electrons perturbed by the periodic lattice potential. All relevant data are collected in a table in which it is seen that in sodium, potassium, rubidium and caesium the wave-length of the upper limit of the absorption band in the visible and near ultra-violet is proportional to the square of the lattice constant, while lithium occupies an anomalous position. The facts at present available do not permit a completely definite test of the absolute values of these wave-lengths given by the theory.

scholarly journals Electronic stopping of protons in xenon plasmas due to free and bound electrons

2013 ◽  
Vol 31 (1) ◽  
pp. 105-111 ◽  
Author(s):  
Manuel D. Barriga-Carrasco ◽  
David Casas
Keyword(s):  
Oscillator Strength ◽  
Close Agreement ◽  
Noble Gases ◽  
Previous Literature ◽  
Free Electrons ◽  
Hartree Fock ◽  
Plasma Target ◽  
Strength Functions ◽  
Bound Electrons

AbstractIn this work, proton stopping due to free and bound electrons in a plasma target is analyzed. The stopping of free electrons is calculated using the dielectric formalism, well described in previous literature. In the case of bound electrons, Hartree-Fock methods and oscillator strength functions are used. Differences between both stopping, due to free and bound electrons, are shown in noble gases. Then, enhanced plasma stopping can be easily estimated from target ionization. Finally, we compare our calculations with an experiment in xenon plasmas finding a close agreement.

scholarly journals Multiply ionized carbon plasmas with index of refraction greater than one

2007 ◽  
Vol 25 (1) ◽  
pp. 47-51 ◽  
Author(s):  
J. FILEVICH ◽  
J. GRAVA ◽  
M. PURVIS ◽  
M.C. MARCONI ◽  
J.J. ROCCA ◽  
...  
Keyword(s):  
Laser Interferometry ◽  
General Assumption ◽  
Capillary Discharge ◽  
Index Of Refraction ◽  
Carbon Ions ◽  
Free Electrons ◽  
X Ray ◽  
Computer Calculations ◽  
Approximation Analysis ◽  
Bound Electrons

For decades the analysis of interferometry have relied on the approximation that the index of refraction in plasmas is due solely to the free electrons. This general assumption makes the index of refraction always less than one. However, recent soft x-ray laser interferometry experiments with Aluminum plasmas at wavelengths of 14.7 nm and 13.9 nm have shown fringes that bend the opposite direction than would be expected when using that approximation. Analysis of the data demonstrated that this effect is due to bound electrons that contribute significantly to the index of refraction of multiply ionized plasmas, and that this should be encountered in other plasmas at different wavelengths. Recent studies of Silver and Tin plasmas using a 46.9 nm probe beam generated by a Ne-like Ar capillary discharge soft-ray laser identified plasmas with an index of refraction greater than one, as was predicted by computer calculations. In this paper we present new interferometric results obtained with Carbon plasmas at 46.9 nm probe wavelength that clearly show plasma regions with an index of refraction greater than one. Computations suggest that in this case the phenomenon is due to the dominant contribution of bound electrons from doubly ionized carbon ions to the index of refraction. The results reaffirm that bound electrons can strongly influence the index of refraction of numerous plasmas over a broad range of soft x-ray wavelengths.

scholarly journals The theory of the transport phenomena in metals

1950 ◽  
Vol 203 (1072) ◽  
pp. 75-98 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Electric Power ◽  
Electrical Resistance ◽  
Free Electrons ◽  
Thermo Electric ◽  
Intermediate Temperature Range ◽  
Order Of Magnitude ◽  
Impure Metal ◽  
Ionic Lattice ◽  
The Ideal

Exact expressions, valid for all temperatures, are obtained in the form of infinite determinants for the electrical conductivity, the thermal conductivity and the thermo-electric power of a degenerate gas of quasi-free electrons interacting with the ionic lattice of a metal. It is shown that the values of the electrical and thermal conductivities, in general, exceed the values given by the approximate interpolation formulae due to Bloch (1930), Wilson (1937) and others, and, in particular, that the Grüneisen-Bloch formula for the ideal electrical resistance is appreciably in error in the region close to the Debye temperature. It is further shown that the residual and ideal resistances of an impure metal are not strictly additive in the region where the two are of the same order of magnitude. The behaviour of the thermal conductivity is shown to agree qualitatively with the discussion based on Wilson’s formula given by Makinson (1938); the numerical values of the thermal conductivity, however, are increased appreciably, particularly for an ideal metal at low temperatures. The thermo-electric power is also discussed, but no simple results can be given for the intermediate temperature range.

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