Researchers at the Paul Scherrer Institute (PSI) announced they have created a synthetic material with magnetic properties capable of changing states – just as water changes from solid ice to liquid or steam – with temperature change.
Honeycomb of nanomagnets
The magnets are only 63 nanometres long and shaped roughly like grains of rice. The researchers used a highly advanced technique to place 1 billion of these tiny grains on a flat substrate to form a large-scale honeycomb pattern. The nanomagnets covered a total area of five by five millimetres.
Thanks to a special measuring technique, the scientists initially studied the collective magnetic behaviour of their metamaterial at room temperature. Here there was no order in the magnetic orientation: the magnetic north and south poles pointed randomly in one direction or another.
When the researchers cooled the metamaterial gradually and constantly, however, they reached a point where a higher order appeared: the tiny magnets now noticed each other more than before. As the temperature fell further, there was another change towards an even higher order, in which the magnetic arrangement appeared almost frozen. The long-range order of water molecules increases in a similar way at the moment when water freezes into ice. “We were fascinated by the fact that our synthetic material displayed this everyday phenomenon of a phase transition,” says Heyderman