Unusual 'Short-Range Order' in Conduction-Electron Spins Discovered at a Record Temperature
—A New Metallic State in the New Material Mn3RhSi?—
In magnetic materials, electron spins in the paramagnetic phase are in a disordered state where the spins are uncorrelated with each other, but when antiferromagnetism appears after a phase transition at low temperature, the spins align in an anti-parallel fashion throughout the material, resulting in a long-range order. In some metallic magnetic materials, an unusual short-range order in conduction-electron spins, where an ordered state emerges partially in the paramagnetic phase, has been observed at low temperature as a property not seen in ordinary metals. However, its origin is not well understood.
We predicted that one of its origins was the spatial inversion symmetry breaking. To verify this prediction, we have thus synthesized Mn3RhSi (manganese3-rhodium-silicon), a new material without spatial inversion symmetry, for the first time in the world. As a result of complementary neutron and muon spin relaxation experiments on Mn3RhSi, we discovered a “partial short-range order of conduction-electron spins” at a record temperature of 720 K (447°C).
This discovery is expected to lead to further understanding of the partial order of conduction-electron spins, the origin of which has not been clarified. It is also expected that this new metallic state may lead to the find of new undiscovered phenomena such as a peculiar magnetic field dependence.