  Skyrmions in ultrathin ferromagnetic metal (FM)/heavy metal (HM) multilayer
systems produced by conventional sputtering methods have recently generated
huge interest due to their applications in the field of spintronics. The
sandwich structure with two correctly-chosen heavy metal layers provides an
additive interfacial exchange interaction which promotes domain wall or
skyrmion spin textures that are N\'eel in character and with a fixed chirality.
Lorentz transmission electron microscopy (TEM) is a high resolution method
ideally suited to quantitatively image such chiral magnetic configurations.
When allied with physical and chemical TEM analysis of both planar and
cross-sectional samples, key length scales such as grain size and the chiral
variation of the magnetisation variation have been identified and measured. We
present data showing the importance of the grain size (mostly < 10nm) measured
from direct imaging and its potential role in describing observed behaviour of
isolated skyrmions (diameter < 100nm). In the latter the region in which the
magnetization rotates is measured to be around 30 nm. Such quantitative
information on the multiscale magnetisation variations in the system is key to
understanding and exploiting the behaviour of skyrmions for future device
applications.
