Was going to put this up a couple of days ago but was a bit preoccupied. So here goes. Imagine that you take a single crystal of Iron, a whisker, and bend it around to make a circle. How could you find out if the crystal was magnetized? Remember, all the magnetic field is contained inside the crystal. The usual way to find out if is is magnetized is to wrap a current loop and a sense loop around it and apply a current, if it was magnetized in that direction the sense loop would not generate a voltage, if not magnetized at all or in the opposite direction then a voltage would be induced, the amplitude being different for the two cases. Can you describe a "nondestructive" way of telling whether the crystal is magnetized?