Natural crystals often conceal extraordinary physics—and atacamite is no exception. This emerald‑green copper mineral, first identified in Chile’s Atacama Desert, hosts chains of copper ions arranged in “sawtooth” triangles. Each ion’s unpaired electron behaves like a tiny compass needle, and their triangular layout prevents all spins from aligning antiparallel, called “magnetic frustration.”

A collaboration between TU Braunschweig and Helmholtz‑Zentrum Dresden‑Rossendorf probed atacamite under intense magnetic pulses. Remarkably, the mineral’s temperature plunged by almost half when exposed to a strong magnetic field, demonstrating an exceptionally large magnetocaloric effect at temperatures below 9 K (−264 °C). Such a dramatic cooling response in a frustrated system was unprecedented.

Further experiments across Europe’s Magnetic Field Laboratory used magnetic resonance spectroscopy to reveal that applied fields dismantle atacamite’s fragile spin order. Rather than stabilizing alignment—as seen in many frustrated magnets—the field decouples adjacent sawtooth chains by fixing tip‑chain spins, erasing long‑range order. Numerical simulations confirmed that this sudden loss of magnetic order drives a rapid drop in magnetic entropy, which the crystal compensates for via a sharp temperature decrease.

While atacamite itself won’t become the next industrial refrigerant, its behavior uncovers a new mechanism for magnetic cooling, instead of the conventional gas‑compression refrigerating systems. By targeting similarly frustrated materials, researchers may discover other compounds with strong, eco‑friendly cooling capacities, which could pave the way for next‑generation refrigeration technologies.