Influence of topology on the phase transition of a ferromagnetic metal.
basic_science · Level V
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- Record sourced from PubMed, PMID 37639599.
- Also identified by DOI 10.1073/pnas.2302466120 and PMC identifier 10483617.
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Abstract
The topological ferromagnet CoS<sub>2</sub> exhibits an anhysteretic, weakly first-order transition at the Curie temperature of 119.8 K with a tricritical point µ<sub>0</sub><i>H</i><sub>tcp</sub> at 0.034 T. Magnetic symmetry and the mixing of majority and minority spin <i>e</i><sub>g</sub> bands at a subband crossing just above the Fermi level produce a topological component of the magnetization that leads to a negative <i>M</i><sup>3</sup> term in the Landau free energy. The position of the Fermi level relative to the subband crossing is critical for controlling the order of the transition. Hole doping in Co<sub>0.89</sub>Fe<sub>0.11</sub>S<sub>2</sub> drains the minority-spin <i>e</i><sub>g</sub> pocket and results in a normal second-order phase transition. Electron doping in Co<sub>0.94</sub>Ni<sub>0.06</sub>S<sub>2</sub> raises the Fermi level toward the subband gap, producing a strongly first-order transition with 15 K hysteresis. Our results demonstrate a relation between topological electronic structure and thermal hysteresis at the Curie point, which may help in the search for magnetocaloric materials.