The neodymium iron boron Nd2Fe14B magnet has the strongest magnetic properties under the same volume conditions and is determined by the substances that make up it. Of course, he is not the strongest in quality. Electromagnet is strong enough, but he is not a permanent magnet, but he is still not as strong as NdFeB in volume ratio (but the electromagnet is bigger, it is stronger than NdFeB magnet, when it is small, it is better than ). Of course, superconducting magnets made by superconducting technology are excluded. Superconducting there is no way to make it clear that the resistance is close to or almost zero.