Magnetic Properties Of Iron Research Articles

The Band Structure of Body-centred Cubic Transition Metals

The theory of the magnetic properties of iron put forward by Mott and Stevens made a number of assumptions about the band structures of the body-centred cubic 3d transition metals. The purpose of the present paper is to give an account of a theoretical study which has been made to see what could reasonably be expected on fairly general grounds about the band structures. It then becomes possible to see more clearly what innovations are required for the Mott and Stevens theory. The method used is essentially a tight binding method, with the feature that the functions used are not located at lattice sites but are on the links joining nearest neighbour lattice points. It leads to an 8 × 8 matrix for the lattice potential for each value of K. A discussion of the diagonalization of this 8 × 8 matrix is given for a number of symmetry points and directions in K-space, and it is shown that a good deal of valuable information can be obtained from relatively simple ideas. It is also shown that the band structure so obtained is incomplete because two of the d-functions are omitted, and these are then included by perturbation methods. The Mott and Stevens model of iron is shown to follow from assumptions about the results of this perturbation treatment. A discussion is given of the ground state determinantal functions for vanadium, chromium and iron which it is hoped will be of use in interpreting the physical properties of these elements. Apart from the value the theory may have in its application to the above metals, the algebraic treatment provides an elegant example of the effects of symmetry on band structures, previously thoroughly discussed in terms of groups by Bouckaert, Smoluchowski and Wigner.

Magnetic Properties of Iron and Copper in Cytochrome Oxidase.

Magnetic Properties of Iron and Copper in Cytochrome Oxidase.

Colors and Magnetic Properties of Iron in Glasses of Various Types and Their Implicationsoncerning Structure: II, Cabal Glasses

The effect of changes in the glass structure on the colors and magnetic susceptibilities of iron was studied in glasses made of CaO, B2O3, and Al2O3 (cabal glasses). As the number of gaps in the structure increased, an increase in the general absorption and a decrease in magnetic susceptibility was observed and was attributed to ferrous iron in network‐forming positions. Further increase in the number of gaps was accompanied by a general increase in transmission as well as by an increase in magnetic susceptibility. This was attributed to the loosening of the structure around the ferrous iron which could easily escape from the interstices and be oxidized to colorless ferric iron taking network‐forming positions. The intensity of the ferrous band depended on the concentration of the ferrous iron and also was affected by the polarizing power of the neighboring cations.

Colors and Magnetic Properties of Iron in Glasses of Various Types and Their Implications Concerning Structure: I, High Alkali Silicate Glasses

The effect of increase of alkali and the replacement of soda by potash and lithia was studied in glasses containing iron and melted under strongly reducing conditions. An increase of alkali in these glasses causes an increase in the absorption throughout the visible spectrum; this is attributed, from magnetic and optical measurements, to Fe2+04 incorporated in the molecular network of the glass structure and having a very low magnetic susceptibility as found in some black spinels (hercynite).

The influence of interstitially dissolved carbon and nitrogen on the magnetic anisotropy of iron and on the mobility of Bloch walls

The influence of interstitial atoms on the magnetic properties of iron was investigated. Two causes for this influence are considered: the magnetostriction and a direct interaction of the interstitial atoms with the magnetization vector. Equations are given for the effect upon the magnetostriction and the magnetic anisotropy. The stabilization of a 90° wall lying in a (110) plane was investigated in detail. It is shown that the stabilizing force on a 90° wall may reach a maximum value that is considerably higher than the value computed for large displacements. The integrals needed in these computations are given in an appendix. These integrals can also be used for calculations on other types of Bloch walls.

The influence of interstitially dissolved carbon and nitrogen on the magnetic anisotropy of iron and on the mobility of bloch walls

The influence of interstitial atoms on the magnetic properties of iron was investigated. Two causes for this influence are considered: the magnetostriction and a direct interaction of the interstitial atoms with the magnetization vector. Equations are given for the effect upon the magnetostriction and the magnetic anisotropy. The stabilization of a 90° wall lying in a (110) plane was investigated in detail. It is shown that the stabilizing force on a 90° wall may reach a maximum value that is considerably higher than the value computed for large displacements. The integrals needed in these computations are given in an appendix. These integrals can also be used for calculations on other types of Bloch walls.

Dr. C. G. Lamb

WE regret to record the death of Dr. Charles George Lamb, emeritus reader in electrical engineering in the University of Cambridge, on May 4. Born in 1867, Lamb originally wished to become a professional musician; when the early death of his father made this impracticable, he went to the University of London, where he attended courses on zoology, and for a time contemplated a medical career; but he ultimately decided to study electrical engineering at the City and Guilds College, where as a student he helped to test the first alternating current transformer that was brought to Great Britain. After graduating, Lamb went to Cambridge in 1891 to assist the late Sir Alfred Ewing in his researches on the magnetic properties of iron; in the same year he was appointed University demonstrator, in mechanism and applied mechanics', a post which he held until he was appointed University lecturer in electrical engineering in 1903.

The Effect of Nascent Hydrogen on the Magnetic Properties of Iron

Hydrogen was electrolyzed into flat ring cathodes of magnetically soft iron in 0.5 N solutions of H2SO4 or of KOH. The design of the electrolytic cell permitted magnetic testing at intervals. Magnetic hardening began after many hours provided the electrolytic current density was kept above a lower limit depending on the electrolyte. This hardening proceeded, at adequate current density, to an end point beyond which longer charging at any current density rarely produced any further changes in magnetic properties. Removal of hydrogen by storage in air at room temperature for 5 months, or by annealing at 400°C in vacuum for 17 hours, did not diminish the magnetic hardness produced during electrolysis. It is suggested that the iron is locally cold-worked by non-uniform distribution in it of hydrogen in excess of the solubility limit at room temperature, and that uniformly distributed hydrogen up to this limit has very little effect on the ferromagnetic properties.

LVI.On a theory of the magnetic properties of iron and other metals

LVI.On a theory of the magnetic properties of iron and other metals

Magnetic and electrical properties of the ternery alloys Fe-Si-C.

The variations in the magnetic properties of iron and iron-alloys, even of supposedly constant composition, have been puzzling to the users and investigators of ferro-magnetic materials ever since the introduction of such materials for electrical apparatus. The author started to investigate this problem over ten years ago at the University of Illinois, and has continued it at the Westinghouse Research Laboratory since 1916, concentrating on iron and iron-silicon alloys. While the results obtained do not eliminate 100 per cent of the difficulties, they go a long way in that direction. It has been found that carbon is largely responsible for the variations, because of the fact that amounts so small as previously to be regarded as traces — less than 0.01 per cent — remain dissolved in the iron in the solid stale, even after slow cooling, and have a tremendous influence on the magnetic properties. Of much less effect is carbon precipitated as pearlite, free cementite and graphite, the effect being in the order named. If the effect of dissolved carbon be represented by 100, the effect of carbon as pearlite is 16.5, of carbon as Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> C 2.25, and of carbon as graphite nearly nil. The form assumed by carbon — aside from the carbon in solution — depends largely on the silicon content, and can best be explained by referring to Fig. 9. Besides carbon, it has been found that the grain size has a large and definite influence on the magnetic properties, due to the accompanying intercrystalline amorphous cement that may be regarded as an impurity similar to other intercrystalline impurities. The detrimental effect of sulphur, phosphorous and manganese on pure iron is in the order named, while phosphorous has a beneficial effect on high silicon alloys. The evidence obtained is to the effect that the increased reluctivity, coercive force, or hysteresis loss, due to carbon and other impurities that are precipitated combined with iron — including in this class the inter-crystalline cement — is caused by the inherent corresponding property of these precipitated impurities. Regarding the tremendous effect of carbon in solution, it is suggested that this is due to the entering of carbon into the more or less stable equilibrium arrangement of the ferro-magnetic structure, upsetting this equilibrium arrangement.

Magnetic and electrical properties of the ternery alloys Fe-Si-C.

The variations in the magnetic properties of iron and iron-alloys, even of supposedly constant composition, have been puzzling to the users and investigators of ferro-magnetic materials ever since the introduction of such materials for electrical apparatus. The author started to investigate this problem over ten years ago at the University of Illinois, and has continued it at the Westinghouse Research Laboratory since 1916, concentrating on iron and iron-silicon alloys. While the results obtained do not eliminate 100 per cent of the difficulties, they go a long way in that direction. It has been found that carbon is largely responsible for the variations, because of the fact that amounts so small as previously to be regarded as traces — less than 0.01 per cent — remain dissolved in the iron in the solid state, even after slow cooling, and have a tremendous influence on the magnetic properties. Of much less effect is carbon precipitated as pearlite, free cementite and graphite, the effect being in the order named. If the effect of dissolved carbon be represented by 100, the effect of carbon as pearlite is 16.5, of carbon as Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> C 2.25, and of carbon as graphite nearly nil. The form assumed by carbon — aside from the carbon in solution — depends largely on the silicon content, and can best be explained by referring to Fig. 9. Besides carbon, it has been found that the grain size has a large and definite influence on the magnetic properties, due to the accompanying inter crystalline amorphous cement that may be regarded as an impurity similar to other inter crystalline impurities. The detrimental effect of sulphur, phosphorous and manganese on pure iron is in the order named, while phosphorous has a beneficial effect on high silicon alloys. The evidence obtained is to the effect that the increased reluctivity, coercive force, or hysteresis loss, due to carbon and other impurities that are precipitated combined with iron — including in this class the inter-crystalline cement — is caused by the inherent corresponding property of these precipitated impurities. Regarding the tremendous effect of carbon in solution, it is suggested that this is due to the entering of carbon into the more or less stable equilibrium arrangement of the ferro-magnetic structure, upsetting this equilibrium arrangement.

The Magnetic Properties of the Ternary Alloys Fe-Si-C

The variations in the magnetic properties of iron and iron-alloys, even of supposedly constant composition, has been puzzling to the users and investigators of ferro-magnetic materials ever since the introduction of such materials for electrical apparatus. The author started to investigate this problem over ten years ago at the University of Illinois, and has continued it at the Westinghouse Research Laboratory since 1916, concentrating on iron and iron-silicon alloys. While the results obtained do not eliminate 100 per cent of the difficulties, they go a long way in that direction. It has been found that carbon is largely responsible for the variations, because of the fact that amounts so small as previously to be regarded as traces-less than 0.01 per cent-remain dissolved in the iron in the solid state, even after slow cooling, and have a tremendous influence on the magnetic properties. Of much less effect is carbon precipitated as pearlite, free cementite and graphite, the effect being in the order named. If the effect of dissolved carbon be represented by 100, the effect of carbon as pearlite is 16.5, of carbon as Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> C 2.25, and of carbon as graphite nearly nil. The form assumed by carbon-aside from the carbon in solution-depends largely on the silicon content, and can best be explained by referring to Fig. 29.

The Magnetic Properties of Iron, Nickel and Cobalt above the Curie Point, and Keeson's Quantum Theory of Magnetism

The Magnetic Properties of Iron, Nickel and Cobalt above the Curie Point, and Keeson's Quantum Theory of Magnetism

The characteristics of iron in high frequency magnetic fields

Not many years ago it was quite generally believed that iron was unable to follow rapid magnetic changes. Experiments which showed an apparent decrease in the permeability of the iron with an increase in the frequency of the magnetic cycle furnished a basis for a theory that iron was magnetically sluggish. Further and more accurate experiments proved, however, that the effects which had previously been ascribed to a peculiarity of the material were in reality caused by eddy currents in the sample. Theoretical calculations were made which demostrated that eddy currents in an iron test piece increased as the square of the frequency and that for even the lower frequencies it was necessary to use quite thin laminations in magnetic circuits in order to eliminate deleterious effects. Furthermore, it was found that due to eddy currents and the magnetic properties of iron, the magnetization in high frequency fields was confined to a thin surface layer of the piece. This “Magnetic Skin Effect” reduced the cross section of the iron which was magnetically active even though the laminations were extremely thin. Careful experimental measurements compared with theoretical calculations proved that the real permeability of iron remained unchanged at frequencies up to about 10 6 and that previous results had been is serious error due to neglect of the factors mentioned. This fact having been established, efforts were made to see what practical use could be made of iron in high frequency work and to that end some extensive experimental investigations of the saturation curves and core losses were made upon specimens laminated as thinly as was commercially practicable. The resulting data have furnished a basis for design. It is a demostrated fact that the permeability of all metals is unity for the magnetic cycles imposed upon them by heat and light waves. In the region between frequencies of about 10 6, where the true permeability of iron is practically the same as at zero frequency, and frequencies of about 10 10 where the true permeability of iron approaches unity, the experimental values of μ decrease smoothly with the frequency. What happens to μ in the range of frequencies between the lingest heat waves and the shortest Hertzian waves which have yet been made is a question which has many interesting features but which has not yet yielded to the experimenter.

Effect of titanium on the magnetic properties of iron: K. P. Applegate. ( Rensselaer Polytechnic Inst., Engin. and Science Series, No. 5, 1914)

High resolution Hα images and magnetograms (0.2 arc s) of an active region were obtained in alternating time series at 42 s cadences using the Swedish 1-m Solar Telescope on 2004 August 21. The Hα filtergrams reveal an active region filament and surges consisting of thread-like structures which have widths similar to the widths of chromospheric fibrils, both recorded down to the resolution limit in the best images. All observed structures in the active region appear highly dynamic. Fibrils show counterstreaming strongly resembling the counterstreaming threads in filaments.Streaming, along the threads of surges extending more than 10 arc s, is higher in speed (∼20 km s−1) than in the filament and fibrils and appears to flow independently over and above the chromospheric fibrils. Blue shifts seen in the Hα Dopplergrams confirm the outward mass motion of the surges. However, in at least one case, we also see simultaneous downflows from the same site but in the opposite direction and downward toward the chromosphere. We suggest that the site between these two outward and downward flows identifies the place where magnetic reconnection could occur and thereby cause of the surge. This appears to imply that the reconnection site is in the high chromosphere or low corona.

Societies and Academies

LONDON. Royal Society, February 26.—Sir William Crookes, O.M., president, in the chair.—Lord Rayleigh: The diffraction of light by spheres of small relative index.—Prof. H. E. Armstrong and Prof. F. P. Worley: Studies of the processes operative in solutions. XXXI.—Sulphonic acids and sulphuric acid as hydrolytic agents: a discussion of the constitution of sulphuric and other polybasic acids and of the nature of acids. XXXII.—The influence of sulphonates on the hydrolytic activity of sulphonic acids: a contribution to the discussion on the influence of neutral salts.—Prof. H. E. Armstrong, R. T. Colgate, and E. H. Rodd: Morphological studies of benzene derivatives. V.—The correlation of crystalline form with molecular structure: a verification of the Barlow-Pope conception of “valency-volume.”—Prof. E. Wilsen: The magnetic properties of iron when shielded from the earth's magnetism. When iron is subjected to a considerable magnetising force, a species of polarisation is produced which has the effect of reducing the permeability and increasing the dissipation of energy due. to magnetic hysteresis for given values of the magnetic induction. The residual effects can be removed by careful demagnetisation or annealing. It was thought by analogy that the earth's magnetic force would also have a polarising influence upon exposed iron, and this is the subject of the present paper. An effort has been made to remove the residual effects of the earth's magnetism by placing the specimen, which is of ring form, in a magnetic shield, and carefully demagnetising it. The magnetic properties of the material were then examined in the usual manner with a ballistic galvanometer, and a comparison made with those obtained from the exposed or unshielded specimen. It has been found that the permeability of freshly demagnetised and shielded iron, corresponding to a given value of the magnetic induction, is considerably larger than in the case of the unshielded specimen.—Dr. J. N. Pring: The occurrence of ozone in the upper atmosphere. In the Alps, at an altitude of 2100 metres, the mean concentration of ozone is about 2.5 parts by volume in one million of air, and at an altitude of 3600 metres, about five parts in one million of air. In this country the mean quantity found between ground-level and an altitude of 20 kilometres was about two parts by volume in one million. No trace of either hydrogen peroxide or nitrogen peroxide could be detected in these cases. Measurements made in the laboratory on the action of ultraviolet light on air showed that a definite equilibrium amount of ozone is obtained, and that this value increases with fall in temperature, but decreases rapidly with fall in pressure. The formation of hydrogen peroxide or nitrogen peroxide by ultra-violet light radiation could not be detected.—W. A. D. Rudge: A meteoric iron from Winburg, Orange Free State. In this paper some account is given of the structure, and mechanical and magnetic properties, of the Winburg meteorite, which is stated to have fallen in 1881. It appears to be composed of large crystals of ferrite with veins and crystals of an iron nickel alloy. The total amount of nickel is not more than 3 per cent.—W. A. D. Rndge: The electrification produced during the raising of a cloud of dust. During the raising of a cloud of dust a considerable amount of electrification occurs. Insulated conductors held in a stream of dust become charged to a potential of some hundreds of volts. The dust particles seem to be charged by friction amongst themselves, some with positive, others with negative, electricity.—Prof. W. M. Thornton: The electrical ignition of gaseous mixtures. This is an experimental examination of the mechanism of ignition of gaseous mixtures by electric sparks. It is found that there are two distinct types of curve connecting percentage of gas in air and the least current which, when broken, causes ignition by the break-spark. In one, characteristic of continuous currents, the current required is proportional to the percentage of gas present; in the other, of the alternating-current type, it is a quadratic function of the percentage, having a minimum, at the mixture giving combustion, midway between CO and CO2. Ignition by continuous-current break-sparks is largely ionic or electronic, but by alternating currents is more nearly a simple thermal process. The gases examined were hydrogen, carbon disulphide, benzene, alcohol, and the paraffin series up to pentane.

XXXVII. The anhysteretic magnetic properties of iron and nickel Part I. The relation of magnetic intensity to field strength and temperature

XXXVII. <i>The anhysteretic magnetic properties of iron and nickel</i> Part I. <i>The relation of magnetic intensity to field strength and temperature</i>

Magnetic properties of iron under high frequency: E. F. W. Alexanderson ( Electro tech. Zeits., xxxii, 1078.)

Magnetic properties of iron under high frequency: E. F. W. Alexanderson ( Electro tech. Zeits., xxxii, 1078.)

Discussion on magnetic properties of iron at frequencies up to 200,000 cycles. New York, November 13, 1911. (see proceedings for December, 1911)

Discussion on magnetic properties of iron at frequencies up to 200,000 cycles. New York, November 13, 1911. (see proceedings for December, 1911)

Magnetic properties of iron at frequencies up to 200,000 cycles

Magnetic properties of iron at frequencies up to 200,000 cycles