  Implicit models for magnetic coenergy have been proposed by Pera et al. to
describe the anisotropic nonlinear material behavior of electrical steel
sheets. This approach aims at predicting magnetic response for any direction of
excitation by interpolating measured of B--H curves in the rolling and
transverse directions. In an analogous manner, an implicit model for magnetic
energy is proposed. We highlight some mathematical properties of these implicit
models and discuss their numerical realization, outline the computation of
magnetic material laws via implicit differentiation, and discuss the potential
use for finite element analysis in the context of nonlinear magnetostatics.
