- Johanna Jochum: Fluctuating skyrmion textures in cubic chiral magnets
- 16. 3. 2022, 14:10
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Abstract:
The rich magnetic phase diagram of MnSi originates in the hierarchy of well-separated energy scales, which unfold as a function of temperature, magnetic field and pressure. Under decreasing temperature and small magnetic fields, skyrmions emerge from the paramagnetic state via a weak crystallization process.
The application of pressure drives the system to undergo a transition from Fermi liquid to non-Fermi liquid physics despite the absence of quantum criticality. The non-Fermi liquid scaling of the resistivity is observed across a remarkably wide regime in temperature, pressure, and magnetic field and is accompanied by a large topological Hall contribution that connects with the skyrmion lattice at ambient pressure.
Substitutional doping of MnSi results in the suppression of magnetic order, where quantum critical behavior is masked by the influence of disorder. Combining ac susceptibility, specific heat, and neutron resonance spin-echo spectroscopy on single-crystal MnSi, we show that up to x = 0.10 static helimagnetic order in zero magnetic field emerges through a Brazovskii-type fluctuation-induced first-order phase transition. For x = 0.12, the transition vanishes and fluctuations prevail down to temperatures of 50mK. The dynamic character is preserved under applied magnetic field, where ac susceptibility, small-angle neutron scattering, and a large topological Hall contribution indicate the formation of fluctuating skyrmion textures that may compare with the topological non-Fermi liquid behavior observed in MnSi under hydrostatic pressure.