Magnetic Construction Set: Unexpected Flexibility of Atomic Layers ⚡ экспресс
Most kagome magnets have a hexagonal structure. In this work, single crystals of the orthorhombic modification RFe₆Ge₆ were grown, where replacing atoms with Ge₂ dimers slightly distorts the kagome lattice. The magnetic subsystems of iron and rare earths behave independently: iron forms ferromagnetic layers with antiferromagnetic stacking above 400 K, while rare earths order below 9 K (in DyFe₆Ge₆, two transitions occur due to the crystal field). DFT calculations show that the energetics of R–Ge₂ chains differ greatly at different scales, and the ferromagnetism of the layers is linked to a high density of states at the Fermi level. This paves the way for studying the relationship between geometry and magnetism.
The new magnetic material is structured like a stack of pancakes: in each layer, all atomic 'arrows' point the same way, but the neighboring layer is magnetized in the opposite direction. The pattern of triangles — a kagome lattice — is distorted because some atoms were replaced with germanium dumbbells. Rare-earth atoms display magnetic order only at temperatures around -264°C, for which liquid helium is used. X-ray diffraction (a method developed by Bragg) and spectroscopy allowed scientists to unveil this structure.
Calculations revealed unexpected flexibility: flipping the entire layer requires a prohibitively large energy, while rotating a single chain of atoms inside the layer is easy. This order dramatically reduces entropy — a measure of disorder. This paves the way for controlled creation of magnetic patterns for future quantum devices.
🎯 The word 'kagome' translates from Japanese as 'woven basket' — exactly the pattern of triangles that the atoms form.