It is pointed out that, contrary to some claims in the literature, the domain
walls cannot be a source of a correlated at large scales primordial magnetic
field, even if the fermionic modes bound on the wall had ferromagnetic
properties. In a particular model with massive (2+1) dimensional fermions bound
to a domain wall, previously claimed to exhibit a ferromagnetic behavior, it is
explicitly shown that the fermionic system in fact has properties of a normal
diamagnetic with the susceptibility vanishing at high temperature.Comment: 8 pages. Modified discussion of the baryon density on an axion domain
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