Scientists switch on a strange new form of magnetism in an ultrathin material

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Scientists have found evidence that a material long considered nonmagnetic can host an unusual form of magnetism when it is squeezed into an ultrathin film. Ruthenium dioxide normally shows no magnetic ordering in its bulk form. But when grown only a few atomic layers thick and placed under physical strain, its electrons arranged themselves in patterns consistent with altermagnetism, a recently proposed magnetic state that could one day make computer memory smaller, faster, and more efficient.

Altermagnetism was proposed only in recent years as a distinct way spins can be arranged inside a material. Unlike a ferromagnet, which has a net magnetic field, an altermagnet can keep zero net magnetization while still producing the spin-dependent electronic behavior that spintronics and next-generation memory devices would rely on. Ruthenium dioxide was one of the first materials put forward as a candidate, but earlier experiments on bulk samples never turned up the expected magnetism.

Rice University physicist Ming Yi, working with Bharat Jalan of the University of Minnesota and Milan Radovic of the Paul Scherrer Institute, reported the findings in Science Advances. “Ruthenium dioxide was one of the first materials to be proposed as an altermagnetic candidate, but studies on its bulk form didn’t return evidence of magnetism,” said Yi, an associate professor of physics and astronomy.