Magnetic Susceptibility

Abstract

The susceptibility of a body to the acquisition of a magnetic moment when exposed to a magnetic field, H _a , is its magnetic susceptibility, χ Ξ M/H _a , where M is its magnetization. In the nonrationalized c.g.s. system of units usually employed by physicists and chemists when studying this subject, the induction, B, within the body is given by B = H _a + 4πM such that its permeability, µ Ξ B/H _a , is 1 + 4πχ ^v . The superscript, v, is here used to denote a “per unit volume (cm³) quantity.” Other commonly employed bases for calculation and measurement are the gram and the mole, the susceptibilities corresponding to which are here denoted by χ^g and χ, respectively. The latter, unsuperscripted, symbol will also be used in the general case (just as heat capacity is the general counterpart of specific heat, to be discussed in the following chapter). In the c.g.s.-e.m.u. system, in which magnetic susceptibility is expressed in e.m.u. per unit mass, volume, etc., the unit of e.m.u. is cm³; thus, χ ^v is dimensionless.