Principal Magnetic Susceptibilities Research Articles

The principal paramagnetic susceptibilities of potassium ferricyanide at low temperatures

The author's previous measurements of the principal magnetic susceptibilities of potassium ferricyanide have been repeated and extended to a temperature of 14.2° K. Two of the principal susceptibilities are approximately equal throughout the whole temperature range from 290 to 14° K., but that along the third principal axis is considerably smaller. The anisotropy is almost 400 per cent at 14° K. and is still increasing as the temperature falls. A brief comparison with Howard's theory of the magnetic properties of K3 [Fe (CN)6] is made.

The Principal Magnetic Susceptibilities of K3Fe(CN)6

The magnitudes, anisotropy and temperature dependence of the principal magnetic susceptibilities of K3Fe(CN)6 are calculated by the method of crystalline potentials, and prove to be in good agreement with experiment. The assumption is made that the interatomic forces in the Fe(CN)6--- complex destroy Russell-Saunders coupling. This results in a susceptibility corresponding to one free electron spin with a contribution, except at very low temperatures, from the unquenched orbital angular momentum. The effect of the latter is sufficient to make the susceptibility at room temperature almost twice as large as the value which would be obtained if the spin alone were considered. The superposition of a small rhombic crystalline field suffices to produce the large observed magnetic anisotropy. The behavior of the susceptibility of K3Fe(CN)6 is in sharp contrast to the higher effective magneton numbers and magnetic isotropy of many ferric compounds, such as the sulphates. In these the ground state of Fe+++ is the normal state of the free ion, namely a 6S state, so that five spins contribute to the susceptibility. Although the calculations ostensibly use the method of crystalline potentials, they are really based on general group properties and so apply even if the bonds in the cyanide are covalent, as they probably are, rather than ionic.

The Magnetic Anisotropy of Crystals of Sn, and of Sn with Added Sb, Cd, or Ga

The principal magnetic susceptibilities of single crystals of white (tetragonal) tin have been determined. Crystals were grown by the traveling furnace method. Perpendicular to the tetragonal axis the susceptibility (per unit volume) is ${\ensuremath{\kappa}}_{\ensuremath{\perp}}=0.197\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$; parallel to the axis it is ${\ensuremath{\kappa}}_{\ensuremath{\parallel}}=0.176\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. The ratio $\frac{{\ensuremath{\kappa}}_{\ensuremath{\perp}}}{{\ensuremath{\kappa}}_{\ensuremath{\parallel}}}$ is strongly influenced by the addition of small amounts of certain elements. For tin containing no added element this ratio is 1.120. Adding 0.60 percent Sb the ratio is 1.200; 0.76 percent Cd, 0.923; 0.89 percent Ga, 0.897. The relation between the change in this ratio and the number of valence electrons of the added element is compared with available data for bismuth.

IX—investigations on magne-crystallic action III—Further studies on organic crystals

In Part I* of this paper a convenient method of measuring the principal magnetic susceptibilities of single crystals was described, and several organic crystals, among others, were studied by this method. The results were discussed particularly in relation to the structure of the molecules and their orientations in the crystal lattice, and it was shown how a correlation of the principal magnetic susceptibilities of the crystal with those for the individual molecules (obtained from measurements on magnetic double-refraction in the liquid state, or from considerations of molecular structure) gives us useful information regarding the orientations of the molecules in the crystal lattice. Indeed, in favourable cases the molecular orientations may thus be determined much more easily, and some of the parameters defining the orientations also more accurately, than by X-ray methods of analysis. Conversely, where the molecular orientations in the crystal lattice are already known from X-ray studies, a knowledge of the principal magnetic susceptibilities of the crystal enables us to obtain the magnetic constants of the individual molecules, which are of interest. For example, it is thus found that as one proceeds from benzene to naphthalene and from naphthalene to anthracene, the numerical increase in susceptibility that occurs, is directed predominantly along the normal to the plane of the benzene rings

Variation of the Principal Magnetic Susceptibilities of Certain Paramagnetic Crystals with Temperature

Variation of the Principal Magnetic Susceptibilities of Certain Paramagnetic Crystals with Temperature

The principal magnetic susceptibilities of some paramagnetic crystals at low temperatures

Our knowledge of the temperature variation of the principal susceptibilities of paramagnetic crystals is as yet fragmentary. The principal susceptibilities of a number of paramagnetic crystals have been determined by Finke and by Rabi at room temperature but the first measurements on orientated crystals over any range of temperature were those of Foëx. He has published the principal susceptibilities of siderose (a mineral which is mainly ferrous carbonate but which contains appreciable quantities of the carbonates of manganese and other metals) over the range 87° to 400°K. and some measurements but not actual principal susceptibilities for manganese sulphate, MnSO 4 .4H 2 O. The writer measured the principal susceptibilities of cobalt ammonium sulphate and nickel sulphate, NiSO 4 . 7H 2 O over the temperature range 14°-290°K. and the writer and de Haas have published measurements on manganese ammonium sulphate crystals over the restricted range 14°-20° K. In addition Dupouy has repeated Foëx’s observations on siderose and has measured the principal susceptibilities of dialogite (a naturally occurring manganese carbonate) and oligist (Fe 2 O 3 ), all over a small range of temperature above 0° C. Quite recently Bartlett has employed Rabi’s method to determine the principal susceptibilities of the following compounds, CoSO 4 . 7H 2 O, CoSO 4 . (NH 4 ) 2 SO 4 . 6H 2 O, CoSO 4 . K 2 SO 4 . 6H 2 O, CuSO 4 . (NH 4 ) 2 SO 4 . 6H 2 O CuSO 4 . K 2 SO 4 . 6H 2 O, NiSO 4 . (NH 4 ) 2 SO 4 . 6H 2 O over the temperature range —45° to +55°C. In the writer’s opinion, however, Bartlett’s procedure is liable to several objections.

Societies and Academies

LONDON Royal Society, Feb. 23.—G. W. C. KAYE and G. C. SHERRATT: The velocity of sound in gases in tubes. The velocity of sound at 18° C. and 100° C. has been determined by the resonating tube method in six different gases contained in six tubes of adjustable length and of different diameters and materials (glass, copper and carbon). A series of frequencies from 500 to 27,000 cycles per second were provided by a valve oscillator system controlled by a vibrating quartz crystal which also served as a resonance detector. The results indicate that for all the gases the Helmholtz-Kirchoff formula is quantitatively correct in its statement of the influence of tube diameter and frequency on the velocity. The formula does not, however, take cognisance of the influence of the wall surface. In the smooth tubes the reduction in velocity below the free space value was on the average about 10 per cent less and in the rough tubes about 30 per cent more than the formula would indicate.—A. F. HALLIMOND (with E. F. HERROUN): Laboratory determination of the magnetic properties of certain igneous rocks. Specimens from Leicestershire (Charnwood rocks) gave low values, but a measurable degree of permanent magnetisation and susceptibility was found for the Cleveland Dyke and for the dyke at Lornty in Perthshire. A method is developed for calculating the magnetic profile from the geological model assuming uniformity of magnetisation. Calculated and observed curves for the Lornty profiles show a fairly good agreement; they indicate that the north side of the dyke is south-polar, so that the magnetisation appears to be in the opposite sense to that recorded for certain dykes in Germany, and is opposite to that which would be produced by cooling in the earth's present field.—L. C. JACKSON: The principal magnetic susceptibilities of some paramagnetic crystals at low temperatures. An apparatus is described for the rapid determination of the principal susceptibilities of crystals at low temperatures with an accuracy of 0.5 to 1 per cent. Results are given for the following crystals: manganese ammonium sulphate, manganese sulphate (penta- and tetrahydrate) ferric acetylacetonate, potassium ferrioxalate, cobalt sulphate and potassium ferricyanide. In agreement with recent theory, the crystals containing ions with s-moment only present or effective are found to be magnetically isotropic to within about 1 per cent. Over the range of temperature employed, 290° — 75° K, the 1/x-T curves for the principal susceptibilities of cobalt sulphate are straight lines, but these are not all parallel.

Variation of the Principal Magnetic Susceptibilities of Certain Paramagnetic Crystals with Temperature

Curie and Weiss Constants for the Principal Susceptibilities of Certain Crystals. The Curie and Weiss constants, respectively ${C}_{m}$ and $\ensuremath{\Delta}$ of the equation ${x}_{m}=\frac{{C}_{m}}{(T+\ensuremath{\Delta})}$, over the temperature range 60\ifmmode^\circ\else\textdegree\fi{} to -45\ifmmode^\circ\else\textdegree\fi{}C have been determined for 5 crystals of the isomorphic monoclinic double sulphate series [M ${\mathrm{R}}_{2}$${(\mathrm{S}{\mathrm{O}}_{4})}_{2}$ 6${\mathrm{H}}_{2}$O] containing cobalt, nickel, or copper, and for cobalt sulphate heptahydrate. The measurements were made by Rabi's method of determining the principal magnetic susceptibilities of crystals, which was found applicable over this temperature range. The use of ethyl alcohol as a solvent for the auxiliary paramagnetic salt permitted the extension of the method to temperatures below the freezing point of water solutions, such as those used by Rabi, for crystals of volume susceptibilities less than 35\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}6}$. The lower limit of the applicability of the method depends only on the availability of low freezing point solutions of sufficient susceptibility. In general the Curie constants for the principal susceptibilities of any given crystal were very nearly the same. The Weiss constant showed considerable variation, both between the different principal magnetic axes of the same crystal, and from one crystal to another. Both the Curie and Weiss constants decreased progressively as the metal ion was changed from cobalt to nickel to copper. The effect of change in the alkali ion from N${\mathrm{H}}_{4}$ to potassium was less pronounced, although there was a slight tendency for the Curie constant to increase and for the Weiss constant to become more positive. The accuracy claimed for the measurements is 1 percent. In general there was a small continuous change in the orientation of the principal magnetic axes in the plane of symmetry of the crystal with respect to the crystallographic axes as the temperature was varied.

The Principal Magnetic Susceptibilities of Bismuth Single Crystals

The Gouy method is used to determine the principal magnetic susceptibilities of bismuth single crystals grown by the method developed by Goetz. The specific susceptibility is shown to be a constant in all directions perpendicular to the principal crystallographic axis with a value of —1.487×10^(-6). Parallel to the main axis the specific susceptibility is a minimum and has the value —1.046×10^(-6). The mean is given then as —1.340×10^(-6).

On the Principal Magnetic Susceptibilities of Crystals

On the Principal Magnetic Susceptibilities of Crystals