Location, Location, Location...

Researchers have shown that the same atom can have different roles in magnetism, depending on its location in the crystal structure. The complex metallic compound Gd5Ge4 has a crystal structure with three distinct sites for its gadolinium atoms. Systematically replacing the gadolinium with other atoms on different sites in the structure may produce radical changes in the magnetic properties, including the catastrophic loss of ferromagnetism when even a little gadolinium is replaced on one specific site, while this does not occur when substituting gadolinium in between the nanolayers that form this compound (Gd2 and Gd3 sites). This demonstrates that ferromagnetism in this alloy is uniquely associated with gadolinium in the so-called Gd1 sites. The findings match and confirm first-principles theoretical results, and open a new set of considerations for theoretically-inspired magnetic alloy design. Alloys based on Gd5Ge4 are candidates for the active elements of magnetic refrigeration devices, which promise the avoidance of atmospheric pollutants in their manufacture and recycling, along with high efficiency and low noise in their operation.

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