Skyrmion-hosting multilayer stacks are promising avenues for applications, although little is known about the depth dependence of the magnetism. We address this by reporting the results of circular dichroic resonant elastic x-ray scattering (CD-REXS) and low-energy muon-spin relaxation (LEµ + SR) measurements on a stack comprising Ta/[CoFeB/MgO/Ta]16 on a Si substrate. Energydependent CD-REXS shows a continuous, monotonic evolution of the domain-wall helicity angle with incident energy, consistent with a three-dimensional hybrid domain-wall-like structure that changes from Néel-like near the surface to Bloch-like deeper within the sample. LE-µ + SR reveals that the magnetic field distribution in the first six layers of the stack is distinct from that in layers further from the surface, quantifying the depth at which the static and dynamic magnetic structure varies. By increasing the applied magnetic field, we find a reduction in the volume occupied by domain walls at all depths, consistent with a crossover into a region dominated by skyrmions above approximately 180 mT.

We present magnetization and muon-spin spectroscopy measurements of Néel skyrmion-host GaV4S8 under the application of hydrostatic pressures up to P = 2.29 GPa. Our results suggest that the magnetic phase diagram is altered with pressure via a reduction in the crossover temperature from the cycloidal (C) to ferromagnetic-like state with increasing P , such that, by 2.29 GPa, the C state appears to persist down to the lowest measured temperatures. With the aid of micromagnetic simulations, we propose that the driving mechanism behind this change is a reduction in the magnetic anisotropy of the system, and suggest that this could lead to an increase in stability of the skyrmion lattice.