A crystal the size of half a matchbox was grown in a furnace, where a molten zone slowly crept along a rod, leaving perfectly ordered layers behind. Inside this crystal, copper ions sit at the nodes of a triangular lattice, but the triangles are slightly skewed, as if someone pressed on one corner. Each copper ion behaves like a tiny magnetic needle that can point up or down.
At room temperature, the needles jitter chaotically. But when the crystal was cooled to 1.14 kelvin, colder than outer space, they suddenly froze into a unified pattern. It turned out that the pattern is not the classic "pinwheel" of three needles at 120 degrees, which you'd expect on a regular triangle. Instead, the needles lie in a single plane but tilt slightly toward each other: one component of the moment is half the other.
Neutrons passed through the crystal acted like an ultra-sensitive measuring tape: by their scattering, researchers could measure exactly where each needle points. It turned out that the total magnetic moment per copper ion is 0.89 Bohr magneton. This is noticeably less than for a free ion — part of the moment is "eaten" by quantum fluctuations that don't quiet down even at absolute zero.
The distorted triangular lattice is like a slightly out-of-tune piano: instead of a pure chord, it plays an unexpected but harmonious melody. Understanding such melodies isn't just for curiosity: in such materials, scientists search for new states of matter that could be useful for future quantum technologies.
A temperature of 1.14 kelvin is -272°C. At this temperature, thermal motion nearly stops, and quantum effects begin to control the behavior of magnetic needles.