| of a material saturated by a magnetostatic field, the complex permeability when it is subjected to an electromagnetic wave having a circularly polarized field component in the plane perpendicular to the magnetostatic field strength:|
μ+ = μr + κr
μ− = μr − κr
where μr and κr are components of Polder's tensor permeability
NOTE – The subscript of µ corresponds to the sign in the mathematical expression; μ+ is applicable where the field rotates counterclockwise as a function of time when seen in the direction of the applied magnetostatic field; μ− is applicable to the reverse rotation.