Magnetic Hysteresis of the Skyrmion Lattice in MnSi*

Understanding the complex dynamics of skyrmion formation and destruction is key to developing new technologies which make use of them. Here we report the observation of a hysteresis effect associated with forming and destroying the SkL in the chiral magnet MnSi using small angle neutron scattering (SANS). This effect is very small when compared to the applied field of the cryomagnet (~ 1 mT vs 200 mT), but is observable and reproducable by the added precision of a custom built solenoid supplementing the cryomagnet. This hysteresis effect is due to an intrinsic energy barrier associated with forming and destroying the SkL. We have explored the time dependence and magnetic history dependence of the phenomenon to better understand its origin, which we believe to be related to the intrinsic topological energy barrier associated with forming the skyrmions.