Robert Georgii

TL;DR: This study experimentally establishes magnetic materials lacking inversion symmetry as an arena for new forms of crystalline order composed of topologically stable spin states in the chiral itinerant-electron magnet MnSi.

TL;DR: Spin Control Controlling and manipulating the spin of an electron is a central requirement for applications in spintronics and an efficient and simple superconducting-based single-electron transistor that can produce spin current with controlled flow is designed and fabricated.

TL;DR: In this article, a comprehensive small angle neutron scattering study of the magnetic phase diagram of the doped semiconductor was performed and the authors found that the regime of the skyrmion lattice is highly hysteretic and extents over a wide temperature range as may be expected due to the site disorder of the Fe and Co atoms.

Abstract: Two centuries of research on phase transitions have repeatedly highlighted the importance of critical fluctuations that abound in the vicinity of a critical point. They are at the origin of scaling laws obeyed by thermodynamic observables close to second-order phase transitions resulting in the concept of universality classes, that is of paramount importance for the study of organizational principles of matter. Strikingly, in case such soft fluctuations are too abundant they may alter the nature of the phase transition profoundly; the system might evade the critical state altogether by undergoing a discontinuous first-order transition into the ordered phase. Fluctuation-induced first-order transitions have been discussed broadly and are germane for superconductors, liquid crystals, or phase transitions in the early universe, but clear experimental confirmations remain scarce. Our results from neutron scattering and thermodynamics on the model Dzyaloshinskii-Moriya (DM) helimagnet (HM) MnSi show that such a fluctuation-induced first-order transition is realized between its paramagnetic and HM state with remarkable agreement between experiment and a theory put forward by Brazovskii. While our study clarifies the nature of the HM phase transition in MnSi that has puzzled scientists for several decades, more importantly, our conclusions entirely based on symmetry arguments are also relevant for other DM-HMs with only weak cubic magnetic anisotropies. This is in particular noteworthy in light of a wide range of recent discoveries that show that DM helimagnetism is at the heart of problems such as topological magnetic order, multiferroics, and spintronics.

TL;DR: In this paper, small-angle neutron scattering experiments were performed on a bulk single crystal of chiral-lattice multiferroic insulator and the helical spin order with magnetic modulation vector was identified.