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Quantum Matter group


Thomas Gruner and colleagues in the QM group and at the MPI-CPfS in Dresden showed that YbNi2Sn retains high spin entropy down to very low temperatures, much less than 1K, despite being a good metal. On the face of it, this is unexpected, because electrons in metals form a degenerate Fermi gas, and so their entropy decreases linearly with temperature below a temperature scale that corresponds to the electronic bandwidth, usually much larger than room temperature. YbNi2Sn, like some other rare earth intermetallics generally classed as 'Kondo lattice materials', bucks this trend because of the tendency of local moments to be protected on the rare earth site. Because the spin entropy can be controlled by applying a magnetic field, YbNi2Sn is a great refrigerant for adiabatic demagnetisation cooling in the sub-Kelvin range. It is relatively cheap to produce, UHV-bakeable and has high thermal conductivity, which makes it easey to conduct heat in or out. Read more about it in Comm. Materials 5, 63 (2024)