  The search for materials exhibiting nanoscale spiral order continues to be
fuelled by the promise of emergent inductors. Although such spin textures have
been reported in many materials, most of them exhibit long periods or are
limited to operate far below room temperature. Here, we present the real-space
observation of an ordered helical spin order with a period of 3.2 nm in a
non-chiral centrosymmetric helimagnet MnCoSi at room temperature via
multi-angle and multi-azimuth approach of Lorentz transmission electron
microscopy (TEM). A magnetic transition from the ordered helical spin order to
a cycloidal spin order below 228 K is clearly revealed by in situ neutron
powder diffraction and Lorentz TEM, which is closely correlated with
temperature-induced variation in magneto-crystalline anisotropy. These results
reveal the origin of spiral ordered spin textures in non-chiral centrosymmetric
helimagnet, which can serve as a new strategy for searching materials with
nanoscale spin order with potential applications in emergent electromagnetism.
