Electromagnetic stress tensor in ponderable media.

We derive an expression for the Maxwell stress tensor in a magnetic dielectric medium specified by its permittivity epsilon and permeability micro. The derivation proceeds from the generalized form of the Lorentz law, which specifies the force exerted by the electromagnetic E and H fields on the polarization P and magnetization M of a ponderable medium. Our stress tensor differs from the well-known tensors of Abraham and Minkowski, which have been at the center of a century-old controversy surrounding the momentum of the electromagnetic field in transparent materials.