Weak crystallization of fluctuating skyrmion textures in MnSi

Abstract

We report an experimental study of the emergence of non-trivial topological winding and long-range order across the paramagnetic to skyrmion lattice transition in the transition metal helimagnet MnSi. Combining measurements of the susceptibility with small angle neutron scattering, neutron resonance spin echo spectroscopy and all-electrical microwave spectroscopy, we find evidence of skyrmion textures in the paramagnetic state exceeding $10^3$Åwith lifetimes above several 10${}^{-9}$s. Our experimental findings establish that the paramagnetic to skyrmion lattice transition in MnSi is well-described by the Landau soft-mode mechanism of weak crystallization, originally proposed in the context of the liquid to crystal transition. As a key aspect of this theoretical model, the modulation-vectors of periodic small amplitude components of the magnetization form triangles that add to zero. In excellent agreement with our experimental findings, these triangles of the modulation-vectors entail the presence of the non-trivial topological winding of skyrmions already in the paramagnetic state of MnSi when approaching the skyrmion lattice transition.

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• Topological magnon band structure of emergent Landau levels in a skyrmion lattice
• Microwave spectroscopy of the low-temperature skyrmion state in Cu2OSeO3
• Screw dislocations in cubic chiral magnets
• Skyrmion Based Magnonic Crystals
• Kagome lattice promotes chiral spin fluctuations
• New Microscopic Magnetic Hamiltonian for Exotic Spin Textures in Metals
• Megahertz dynamics in skyrmion systems probed with muon-spin relaxation
• Tunable Cooperativity in Coupled Spin--Cavity Systems
• Topological energy barrier for skyrmion lattice formation in MnSi
• Oscillatory magnetic fields for neutron resonance spin-echo spectroscopy
• Direct observations of spin fluctuations in spin-hedgehog-anti-hedgehog lattice states in MnSi${}_{1-x}$Ge${}_x$ ($x=0.6$ and $0.8$) at zero magnetic field
• Anomalous magnetoentropic response of skrymion crystals
• Comparison of skyrmion phases between poly and single-crystal MnSi by composite magnetoelectric method
• Anomalous Hall effect in the antiferromagnetic Weyl semimetal SmAlSi
• Cubic magnetic anisotropy in $B$20 magnets: Interplay of anisotropy and magnetic order in Fe${}_{1-x}$Co${}_x$Si