We report spherical neutron polarimetry (SNP) and discuss the spin-flip scattering cross sections as well as the chiral fraction $η$ close to the helimagnetic transition in MnSi. For our study, we have developed a miniaturised SNP device that allows fast data collection when used in small angle scattering geometry with an area detector. Critical spin-flip scattering is found to be governed by chiral paramagnons that soften on a sphere in momentum space. Carefully accounting for the incoherent spin-flip background, we find that the resulting chiral fraction $η$ decreases gradually above the helimagnetic transition reflecting a strongly renormalised chiral correlation length with a temperature dependence in excellent quantitative agreement with the Brazovskii theory for a fluctuation-induced first order transition.
Wavelength-resolved small-angle neutron spectroscopy of spin waves in MnSi under pressure
Saint Petersburg State University（圣彼得堡国立大学）；Institute for High Pressure Physics, Russian Academy of Sciences（俄罗斯科学院高压物理研究所）；Mozhaisky Military Space Academy（莫扎伊斯基军事航天学院）；Institute of High Energy Physics, Chinese Academy of Sciences (CAS)（中国科学院高能物理研究所）；Dongguan Neutron Science Center（东莞中子科学中心）
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
本研究利用 TOF 中子非弹性散射和 MIEZE 自旋回波技术观测 MnSi$_{1-x}$Ge$_x$ 的 SHAH 晶格态自旋涨落，揭示其与正霍尔电阻率温度区间的对应，支持符号偏置标量自旋手性机制。
