  Two-dimensional magnetic van der Waals (vdW) materials can show a variety of
topological nontrivial spin textures, such as Bloch- or N\'eel-type stripe,
skyrmion or bubble domains under certain external stimuli. It is critical to
understand the magnetic domain behavior in vdW materials in order to control
their size, and density in response to external stimuli such as electric and
magnetic fields. Here we examine the magnetic field dependence of topologically
non-trivial magnetization spin textures in vdW Fe$_3$GeTe$_2$. N\'eel-type
stripe domains and skyrmions are formed depending on the magnetic field-cooling
protocol used during in-situ Lorentz transmission electron microscopy (LTEM)
experiments. Use of quantitative reconstruction of magnetic induction maps, and
micromagnetic simulations, allow for understanding the LTEM results of
N\'eel-type stripe domains as well as skyrmions. In addition, the deformation
of skyrmion contrast is observed as a result of the introduction of an in-plane
magnetic field. We demonstrate the stability of the stripe domains and
skyrmions in response to externally applied magnetic field due to energy
barrier for domain wall annihilation. Our results establish an understanding of
the energy landscape that governs the behavior of the topologically non-trivial
spin textures in vdW materials which can be harnessed for spintronic
applications.
