the most expensive is samarium cobalt magnet

Magnets can be grouped into permanent magnet andmagnetic plate， Permanent magnet may be a natural product, known as lodestone, also be made artificially produced (the strongest magnets are neodymium magnets). The non-permanent magnet, and only under certain conditions be magnetic, usually in the form of an electromagnet to produce, i.e. the use of electric current to strengthen the magnetic field,Soft magnetic core including silicon and soft; hard magnetic including aluminum, nickel and cobalt, samarium cobalt, ferrite and NdFeB, of which, the most expensive is samarium cobalt magnet, the cheapest is a ndfeb magnets