  The synthesis of two-dimensional van der Waals magnets has paved the way for
both technological applications and fundamental research on magnetism confined
to ultra-small length scales. Edge magnetic moments in ferromagnets are
expected to be less magnetized than in the sample interior because of the
reduced amount of neighboring ferromagnetic spins at the sample edge. We
recently demonstrated that CrGeTe3 (CGT) flakes thinner than 10 nm are hard
ferromagnets; i.e., they exhibit an open hysteresis loop. In contrast, thicker
flakes exhibit zero net remnant field in the interior, with hard ferromagnetism
present only at the cleaved edges. This experimental observation suggests that
a nontrivial interaction exists between the sample edge and the interior. Here,
we demonstrate that artificial edges fabricated by focus ion beam etching also
display hard ferromagnetism. This enables us to write magnetic nanowires in CGT
directly and use this method to characterize the magnetic interaction between
the interior and edge. The results indicate that the interior saturation and
depolarization fields depend on the lateral dimensions of the sample. Most
notably, the interior region between the edges of a sample narrower than 300 nm
becomes a hard ferromagnet, suggesting an enhancement of the magnetic exchange
induced by the proximity of the edges. Last, we find that the CGT regions
amorphized by the gallium beam are nonmagnetic, which introduces a novel method
to tune the local magnetic properties of CGT films, potentially enabling
integration into spintronic devices.
