Quantum sensing and imaging of two-dimensional magnets*

The recent discovery of long-range magnetic order in atomically thin ``van der Waals’’ (vdW) crystals [1] has attracted significant attention due to their fundamental and technological interest, including predictions of exotic magnetic phases and unique opportunities to control magnetism at the atomic scale. Yet, nanoscale imaging tools to address spin textures in these magnets have been missing until recently, despite the key role they play for future developments in the field.

 

Here, I will present recent experiments, where we employ single-spin-based quantum sensors for quantitative, nanoscale probing of atomically thin vdW magnets [2]. On one hand, I will describe experiments, where we employ this technology to address magnetism in the prototypical vdW magnet CrI₃ [3], down to the level of atomic monolayers. Our approach enabled nanoscale imaging of magnetic domains, quantitative determination of CrI₃‘s layer-dependent magnetization, and revealed a delicate interplay between magnetic and crystalline order in CrI₃. On the other hand, I will present recent experiments we performed on further members of the family of vdW magnets and on MBE-grown monolayers of the two-dimensional magnet EuGe₂ [4] - a particularly relevant platform due to its potential scalability. In both cases, our results there offered quantitative determination of magnetic moment densities as well as control and direct access to magnetic anisotropies in nanostructured samples.

 

I will conclude with an outlook of future engineering challenges for nanoscale quantum sensors and our ongoing developments of single spin magnetometers for extreme conditions, such as high magnetic fields, millikelvin temperatures, or for high-frequency sensors to probe the dynamics of nanomagnetic systems.

 

[1] B. Huang et al., Nature 546, 270; C. Gong et al, ibid 265

[2] L. Thiel et al., Science 364, 973

[3] M. Gibertini et al., Nature Nanotechnology 14, 408

[4] A. M. Tokmachev et al., Nature Comm., 9, 1672