  Powder samples have been suggested as a pathway to fabricate isotropic
magnetoelectric (ME) materials which effectively only have a pseudoscalar or
monopole ME response. We demonstrate that random distribution of ME grains
alone does not warrant isotropic ME response because the activation of a
non-vanishing ME response requires a ME field cooling protocol which tends to
induce preferred axes. We investigate the evolution of ME susceptibility in
powder chromia samples for various ME field cooling protocols both
theoretically and experimentally. In particular, we work out the theoretical
expressions for ME susceptibility for powder Chromia in the framework of
statistical mechanics where Boltzmann factors weigh the orientation of the
N\'eel vector relative to the local orientation of the c-axis of a grain.
Previous approximations oversimplified the thermodynamic nature of the
annealing process giving rise to misleading conclusions on the role of the
magnitude of the applied product of electric and magnetic fields on the ME
response. In accordance with our refined theory, a strong dependence of the
functional form of $\alpha$ vs. $T$ of Chromia powders on the ME field cooling
protocol is observed. It shows that Chromia powder is not generically an
isotropic ME effective medium but provides a pathway to realize the elusive
isotropic ME response.
