Open AccessA method of measuring magnetic susceptibilities
Author(s) -
P. L. Kapitza,
W. L. Webster
Publication year - 1931
Publication title -
proceedings of the royal society of london. series a, containing papers of a mathematical and physical character
Language(s) - English
Resource type - Journals
eISSN - 2053-9150
pISSN - 0950-1207
DOI - 10.1098/rspa.1931.0111
Subject(s) - magnetic field , magnetic susceptibility , displacement (psychology) , body force , paramagnetism , measure (data warehouse) , physics , nuclear magnetic resonance , condensed matter physics , classical mechanics , computer science , quantum mechanics , psychology , psychotherapist , database
Among the different methods which can be used to measure the magnetic susceptibility of feebly magnetic substances, the most practical, and those most frequently employed at the present time, depend essentially on the measurement of the force acting on the substance when placed in a non-uniform field. This force is given by the well-known formula Fx = χ ∫v 0 Hd H/dx d V, where χ is the volume susceptibility, (H) is the magnetic field,d H/d x is the gradient of the magnetic field in the directionx in which the force is measured at the site of a small element of volume (d V). Corresponding to the wide range of susceptibility, and to the different physical states and conditions which occur, a number of methods of measuring this force have been developed. In all these methods, since they are based on the measurement of the force on the substance, and since it is by the displacement of the body that the force is measured, it is essential that the body should be movable. The force acting on the body is small, usually only a few dynes, and delicate methods have to be used for making the measurements, as, for instance, in the Curie-Faraday method where the substance is carried on a sensitive torsion balance.