[bkraz]

I measured the pure iron powder as well. It shows no measurable area inside the BH curve, which at first seems incorrect since the textbook retentivity value for pure iron is fairly high. The textbook may be referring to a single iron magnetic domain. In a practical sample (even a solid piece of iron, let alone powder in epoxy), there are likely many magnetic domains that cancel each other out, and "soft iron" is used commercially for the very reason that is has extremely low retentivity in bulk.