Strained ultrathin ruthenium dioxide films show magnetic spin textures

A study published in Science Advances finds that very thin layers of ruthenium dioxide can become magnetic when the lattice is placed under strain, phys.org reported. Bulk RuO2 is generally thought to be nonmagnetic, and prior work on thicker or relaxed films produced conflicting claims about magnetic order and possible altermagnetism. The team grew atomically smooth, fully strained 2-nanometer-thick RuO2 films on titanium dioxide-based substrates. Using spin-resolved, angle-resolved photoemission spectroscopy in two measurement geometries, plus X-ray and optical checks of structure and symmetry, they observed an unusual momentum-dependent spin pattern in the strained films. Phys.org said the patterns could not be explained by the film's nonmagnetic polar structure or known measurement artifacts, pointing to intrinsic magnetic order compatible with either weak ferromagnetism or altermagnetism. The authors wrote that symmetry analysis rules out nonmagnetic origins and that the result marks a departure from relaxed or bulk RuO2 behavior. Tests were conducted at a temperature of around 15 kelvin, so room-temperature behavior remains uncertain. The writeup says that if the effect extends and can be controlled, strain-engineered RuO2 could become a platform for low-power spintronic components that use electron spin, offering an adjustable oxide route to sensors, memory and related devices without conventional ferromagnets. The paper is by Yichen Zhang and colleagues, DOI 10.1126/sciadv.aec2917. Spintronics and oxide-electronics groups gain a strain knob on RuO2 magnetism in the ultrathin limit, a material already used as a conductor and electrocatalyst.