A Magnetic Compass Inside a Crystal express
The tiny magnetic arrows inside a crystal of terbium-iridium oxide behave strangely: instead of lying along their preferred axis, they stand across it. This state fully forms when cooled to 1.5 Kelvin — colder than outer space.
Researchers probed the crystal with neutrons and observed how these flipped arrows oscillate and exchange energy. Calculations showed that to explain what they saw, pairwise interactions between terbium ions alone are not enough — one must also account for the influence of the iridium sublattice, which acts like an external magnetic field.
Such materials are interesting not only for fundamental physics. Unusual magnetic states could find use in spintronics — electronics where information is carried not by charges but by the directions of magnetic moments.
A temperature of 1.5 Kelvin is about minus 271.65 degrees Celsius. At such temperatures, thermal motion nearly freezes, and quantum effects come to the fore.