Exotic magnetic textures arising from the subtle interplay between thermodynamic and topological fluctuations have attracted great interest for their possible applications in spintronic devices. Recent advances in electron microscopy make it possible to image random photo-generated individual skyrmions.

However, their deterministic and dynamic manipulation needs to be improved due to the chaotic nature of such fluctuations and the intrinsically irreversible switching between different minima in the magnetic energy landscape. In addition, the visualization and deterministic control of very few spins have yet to be achieved on ultrafast timescales.

Tengdin, Ph.D., graduate student Benoit Truc and fellow postdoctoral fellow Dr. Alexey Sapozhnik have developed a new technique to visualize and control the rotation of a handful of spins arranged in a vortex-like texture at the fastest speed ever achieved.

The scientists achieved this using a series of femtosecond laser pulses (10-15 or one quadrillionth of a second). They were able to control the rotation of the spins in a selenium-copper mineral known in the field for its chemical formula, Cu2OSeO3, by precisely spacing the laser pulses. Due to its great testbed for investigating spins, the mineral is relatively well known in spintronics.

When scientists controlled the spins with laser pulses, they found they could change their orientation at will by changing the delay time between successive drive pulses and adjusting the laser polarization.

The team was also able to image the spin changes thanks to a transmission electron microscope that can “see” small dimensions. The discovery has important implications for the core concepts of spintronics.

Dr. Phoebe Tengdin, a postdoc in Carbone’s lab, said: “Our experiments show that it is possible to manipulate and image a handful of very high-speed spins using a moderate-intensity light beam. Such an effect can be exploited in ultra-fast, low-consumption devices operating on spins work. New types of memories or logic gates are possible candidates, as are high-precision sensors.”

Magazine reference:

  1. Phoebe Tengdin, Benoit Truc, Alexey Sapozhnik, et al. Imaging the ultrafast coherent control of a skyrmion crystal. Physical Review X, Dec 20, 2022. DOI: 10.1103/PhysRevX.12.041030