Scientists from the University of Konstanz in Germany have discovered that a 300-year-old law of friction, previously known as Amontons' first law of physics, does not predict interactions between two magnetic materials. This discovery could help improve micro- and nano-devices that rely on magnetism. The researchers used a two-dimensional array of freely rotating magnetic elements above a second magnetic layer in an experiment to create a regime of competing interactions where the rotors constantly reorganize as they slide. At close and far distances, friction increased at intermediate distances due to competing interactions. The study was published in the journal Nature.