Is the Atom the Ultimate Magnetic Particle?

Abstract

Effect of Magnetization of Crystal on Intensity of X-ray Reflection; Theory.---The intensity of reflection of X-rays from a crystal depends upon the arrangement of the atoms within the crystal and upon the arrangement of the electrons within the atom. If the ultimate magnetic particle is a group of atoms, such as the chemical molecule, magnetization of the crystal will change the orientation of the group and hence change the positions of the individual atoms. If the ultimate magnetic particle is the atom, magnetization will change the orientation of the atom and hence alter the arrangement of the electrons. In either case magnetization of a crystal should be accompanied by a change in the intensity of a beam of X-rays reflected from its surface.Effect of Magnetization of Crystal on Intensity of X-ray Reflection; Experiment.---Such an effect was sought for by reflecting X-rays from a crystal of magnetite and measureing the intensity of the reflected beam by a sensitive balance method. The test was made on the first four orders of reflection from the natural (III) face when the crystal was magnetized perpendicular to its reflecting surface and on the third order when magnetized parallel with this surface. On magnetizing the crystal to $\frac{1}{3}$ of saturation and on demagnetization, no change in intensity of the reflected beam was observed, though a variation of 1 per cent. would have been detected.Molecule as Ultimate Magnetic Particle.---A displacement of the atoms due to magnetization by $\frac{1}{300\mathrm{th}}$ of their distance apart would have produced a detectable effect. This experiment therefore affords a strong confirmation of the conclusion reached by K. T. Compton and E. A. Trousdale that the elementary magnet is not a group of atoms.Motion of Elementary Magnet in Strong Magnetic Field.---An argument is presented which shows that when saturation occurs the elementary magnets very probably have their axes nearly parallel with the direction of magnetization.Atom as Ultimate Magnetic Particle.---Subject to the validity of this conclusion, it is not found possible to explain the negative result of the experiment if the atom as whole acts as the elementary magnet. Certain other explanations are also discussed and found unsatisfactory.Electron or Positive Nucleus as Ultimate Magnetic Particle.---Either of these conceptions is in accord with the result of the experiment, but auxiliary evidence favors the electron as the probable elementary magnet.