I thought about this a little yesterday. I have a small AC electro magnet that was left over from a prototype project of years ago. I placed a small hall sensor close to it and it activated the sensor. I noticed that when power was removed my steel dowel did hang on to the magnet, I don't know how long. However, it did seem to release the instant the LED on my hall effect went out.
I wanted to experiment a little more but yesterday we had an unexpected death on my little street so we gave the family time and everything got screwed up as to my plans. Maybe after work today I can post a few pictures of what I am getting at with all this.
Ron