Time dependent small angle neutron scattering study of metastable skyrmion lattices in B20 systems

Magnetic skyrmion lattices are a form of long range magnetic order with non-trivial topology, which prohibits the continuous deformation in to a ferromagnetic state or, in the case of B20 chiral magnets, helimagnetic order. Regardless of their topological characteristics experimental observations of skyrmion lattices in bulk systems are constrained to a region a few Kelvin wide just below the ordering temperature Tc. However it is possible to obtained metastable skyrmion lattice phases in some chiral magnets by quenching the sample and in some cases by cooling the sample with an applied field of the right magnitude. Here we report a small angle neutron scattering study of such metastable skyrmion lattice phases in a highly disordered (FeCoSi) and a very clean system (MnSi) with special focus in the time dependent stability of the skyrmion lattice as a function of external magnetic field and temperature.