  Controlling magnetism in low dimensional materials is essential for designing
devices that have feature sizes comparable to several critical length scales
that exploit functional spin textures, allowing the realization of low-power
spintronic and magneto-electric hardware. [1] Unlike conventional
covalently-bonded bulk materials, van der Waals (vdW)-bonded layered magnets
[2-4] offer exceptional degrees of freedom for engineering spin textures. [5]
However, their structural instability has hindered microscopic studies and
manipulations. Here, we demonstrate nanoscale structural control in the layered
magnet CrSBr creating novel spin textures down to the atomic scale. We show
that it is possible to drive a local structural phase transformation using an
electron beam that locally exchanges the bondings in different directions,
effectively creating regions that have vertical vdW layers embedded within the
horizontally vdW bonded exfoliated flakes. We calculate that the newly formed
2D structure is ferromagnetically ordered in-plane with an energy gap in the
visible spectrum, and weak antiferromagnetism between the planes. Our study
lays the groundwork for designing and studying novel spin textures and related
quantum magnetic phases down to single-atom sensitivity, potentially to create
on-demand spin Hamiltonians probing fundamental concepts in physics, [6-10] and
for realizing high-performance spintronic, magneto-electric and topological
devices with nanometer feature sizes. [11,12]
