Through new experiments with magnetic materials, physicists in Austria and Hong Kong have overturned a simple law of friction that has held for over 300 years. Led by Clemens Bechinger at the University of Innsbruck, the team’s discovery shows how internal collective dynamics in these materials can cause friction to peak at a certain applied, load before dropping sharply. The effect could prove especially promising in applications where friction needs to be precisely controlled. In 1699, French physicist Guillaume Amontons published his rediscovery of an effect first observed by Leonardo da Vinci: that the force of friction between two sliding surfaces is proportional to the load pressing them together. He also showed that this relationship is monotonic, meaning friction continues to grow as the load increases, forcing stronger interactions between the surfaces. Since then, Amontons’ law has held up to close experimental scrutiny.…