Black magnets

What is a black magnets? What materials can black magnets be?

Just see a netizen asked a question about the black magnet, ask black magnet is what material, with your question, Xiao Fu here to introduce this kind of black magnet. Black magnet, that is, a magnet with a black surface, the commonly used shapes on the market are round sheet, ring, square, with a pass, arc, semicircle, and some irregular shapes and so on....