Topological defects, such as domain walls or skyrmions, are formed when the symmetry of a magnetic material is disrupted. The manipulation of such objects holds promises for high-performance memory devices. 

The direct observation in antiferromagnets at room temperature, however, is very challenging due to extremely weak stray magnetic fields of uncompensated spins. Furthermore, the associated complex spin textures are nanoscale objects, thus requiring excellent spatial resolution.  

Using Scanning NV Magnetometry (SNVM), the team led by Dr. Aurore Finco (Laboratoire Chrales Coulomb – Université de Montpellier and CNRS) observed for the first time topological line defects in multiferroic antiferromagnets at room temperature.

Thanks to the high sensitivity and spatial resolution of Qnami Quantilevers, the team quantitatively imaged the cycloidal antiferromagnetic order at the surface of a bulk bismuth ferrite crystal. They showed the coexistence, within single ferroelectric domains, of antiferromagnetic domains with different directions of the cycloid orientation. At the junctions between the magnetic domains, they observed the complex whirling spin textures demonstrating the presence of topological line defects for the first time in antiferromagnets.

Read the full article in Physical Review Letter.