Magnetism of oxide antiferromagnets (AFMs) has been studied
in
single crystals and extended thin films. The properties of AFM nanostructures
still remain underexplored. Here, we report on the fabrication and
magnetic imaging of granular 100 nm-thick magnetoelectric Cr2O3 films patterned in circular bits with diameters ranging
from 500 down to 100 nm. With the change of the lateral size, the
domain structure evolves from a multidomain state for larger bits
to a single domain state for the smallest bits. Based on spin–lattice
simulations, we show that the physics of the domain pattern formation
in granular AFM bits is primarily determined by the energy dissipation
upon cooling, which results in motion and expelling of AFM domain
walls of the bit. Our results provide a way toward the fabrication
of single domain AFM-bit-patterned memory devices and the exploration
of the interplay between AFM nanostructures and their geometric shape.