Neutron Diffractive Imaging of the Skyrmion Lattice Nucleation in {{MnSi}}

Spatially resolved neutron diffractive imaging with a microchannel plate collimator is used to directly map the nucleation of the skyrmion lattice (SkL) of the B20 compound MnSi at the conical to SkL transition as a function of magnetic field. Our study shows a macroscopic phase separation of the SkL and the conical phase at the border of the SkL phase pocket, reveals that the nucleation of the SkL starts at the edges of the sample, and quantifies the bending of the SkL due to demagnetization. Our study highlights the importance of geometric and demagnetizing effects for the SkL formation regarding the unambiguous interpretation of measurements of bulk properties such as possible phase coexistence and crossover regimes.