EDIT: WRONG CURVE! Found an error!
I've just measured and did calculations. Arrived to a result.
I will publish the methodology and calculation formulas later, verifying them in the process. This is just a kind of teaser.
From this B-H curve, I obtained a permeability of the material of about 2. That is, two times more than that of vacuum. That's absolutely and totally hopeless, I have to say. To consider the material any kind of useful, I need the value of at least 10.
For comparison, typical permeability of transformer core steel is about 4000, according to Wikipedia.
And look at that huge area! This means that losses are huge!
So, the conclusion so far is that the material is useless. Hopefully, I will find a mistake in my crude calculations. But from how it attracts to magnets, I can pretty much tell that permeability=2 is plausible.
I could not achieve saturation with my test coil. This is very much expected considering the very low permeability.