A New Type of Magnetic Birefringence

Abstract

IT is well known that salts of cerium and other rare earths exhibit in aqueous solution a Faraday effect or magnetic gyration of light in the opposite sense to that shown by the great majority of fluids. The phenomenon has been explained by Ladenburg, Becquerel, and others as an effect connected with the paramagnetism of the ions and their orientation by the magnetic field. The study of magnetic gyration in paramagnetic substances generally therefore possesses great interest. Incidentally, also, the question arises if, as has been suggested by Ladenburg, the paramagnetic ions are orientated by the field, whether the solutions should not exhibit magnetic birefringence when observed in a direction transverse to the field. Investigations made on both these points have yielded very interesting results.