SmCo alloys have density 8.2-8.4, so it is unmistakably not SmCo. It would also give off a lot of hydrogen, or require a lot of oxidizer: cobalt
isn't an especially reactive metal, and may require some effort to dissolve (I don't know if this is the case; it is with nickel, but isn't with
iron). It would not simply dissolve in acid.
A density of around 4 is much more suggestive of a ferrite (density 4.8-5.0).
You can determine if it's strontium or barium ferrite by adding a weak solution of a sulfate (sulfuric acid, potassium or ammonium sulfate, etc.) to
the magnet solution. Wash and filter the precipitate (wash with mild acid until it's white and clean), then perform a flame test. Strontium will
glow red, barium green; a mixture will look yellow, but don't mistake this color for the pervasive color of sodium's yellow-orange color (don't use
sodium sulfate, if you can avoid it, because that would be a source of contamination).
Tim |