More than 80% of known magnetic substances have dominant antiferromagnetic interactions. As it generates no stray field, the antiferromagnetic order is very discreet, which makes the processes of nucleation or growth of domains, as well as their responses to external stimuli at the microscopic scale, a virtually uncharted territory. The scarcity of real‑space imaging techniques devoted to this class of magnetic materials is a major bottleneck to understanding the fundamental basis of their manipulation.

In this paper just published in Nature Materials, we use second harmonic generation with unprecedented sub-micron resolution to image antiferromagnetic order in BiFeO3 thin films. We provide a direct visualization of the antiferromagnetic domains in a single ferroelectric one. these antiferromagnetic domains can be manipulated thanks to magnetoelectric coupling in this archetypal multiferroic. More unexpectedly, we are also able  to manipulate the antiferromagnetic domains independently of the ferroelectric polarization, using electric fields significantly lower than the ferroelectric coercivity or  using optical stimuli such as THz pulses generated by a femtosecond laser. This opens horizons to manipulate the antiferromagnetic order in multiferroics and brings new insights into the emerging field of  antiferromagnetic spintronics.

This work was performed in collaboration with CEA-Saclay.

Multi-stimuli manipulation of antiferromagnetic domains assessed by second-harmonic imaging
J.-Y. Chauleau et al ; Nature Mater. 10.1038/nmat4899 (2017)