The ability of certain pieces of rock to attract or repulse each other was discovered about 25 centuries ago by a Greek shepherd whose name was Magnes. Since that time, magnetic properties of materials have fascinated humankind, and quite a few types of magnets have been characterized, synthesized or manufactured. In Physical Review Letters, Hashimoto and co-workers report a unique magnet that reverses magnetization not just once, but twice, as the temperature changes. A simple theoretical approach led to the design and synthesis of this unusual magnet, which is a Prussian blue material incorporating four different metal ions.
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