Asked by: Steve Hills, Manchester
Cut a magnet in two, and you just end up with two smaller magnets, each with a north and a south pole. Yet according to the laws of physics, there’s no reason why single magnetic poles cannot exist. In 1982, researchers at Stanford University, California, thought they’d detected such a ‘monopole’, but the absence of any further discoveries has led most physicists to think this was probably a false alarm. More recently, Claudio Castelnovo of Oxford University, Roderich Moessner of the Max Planck Institute for the Physics of Complex Systems in Dresden and Shivaji Sondhi of Princeton University, have described a system in a lattice of holmium titanate, which appears to allow for a magnetic monopole to wander freely within it at certain temperatures.