Investigation of the spin current induced by magnetic excitation in triple Cr

An innovative approach to developing low-power, high-speed, high-density memory devices is based on spintronics, an emerging frontier in technology that harnesses a degree of electrons’ freedom known as spin. Simply put, electrons, along with their negative charge, have a spin whose direction can be controlled using magnetic fields. This is especially important for magnetic insulators, where the electrons cannot move, but the spin remains controllable. In these materials, magnetic excitation can give rise to spin current, which forms the basis of sigmoidal electronics.

Scientists have been looking for efficient ways to generate spin current. The photogalvanic effect, a phenomenon characterized by the generation of a continuous stream of photoluminescence, is particularly useful in this regard. Studies have found that the optical spin current can similarly be generated using magnetic fields in electromagnetic waves. However, we currently lack the candidate materials and general mathematical formula to explore this phenomenon.

Now, Associate Professor Hiroaki Ishizuka of the Tokyo Institute of Technology (Tokyo Technology), along with his colleague, has addressed these issues. In their recent study published in physical review messages, presented a general formula that can be used to calculate the optical spin current due to transverse oscillating magnetic excitations. They then used this formula to understand how optical spin currents appear in the bilayer chromium (Cr) tri-complex, chromium triiodide (CrI).₃) and chromium tribromide (CrBr₃).

“In contrast to previous studies that considered longitudinal oscillating magnetic fields to generate spin currents, our study focuses on transverse oscillating magnetic fields. Accordingly, we found that processes involving one magnetic band (quantum of spin wave excitation) as well as two magnetic bands contribute to the current. rotation,” explains Dr. Ishizuka.

Using their formula, the duo found that both CrI₃ and CrBr₃ showed a large optical spin current for magnetic excitation corresponding to Electromagnetic waves At frequencies of gigahertz and terahertz. However, the current appeared only when the spins showed antimagnetic order, which means that successive spins were antiparallel, unlike magnetic order (where successive spins are parallel).

Moreover, the direction of the spin current was governed by the orientation of the antimagnetic arrangement (whether the spins on the first and second layers were arranged up or down). In addition, they pointed out that, in contrast to previous results that attributed the spin current to only the magnon process, their formula showed that a large response was, in general, possible with the single-magnon process.

These results indicate that the CrI . bilayer₃ and CrBr₃ They are strong candidates to investigate the mechanism associated with the current generation of photoperiod.

“Our study does not only anticipate unexpected contributions to spin current But it also provides guidelines for designing new materials driven by the optical effect of magnetic excitationDr. Ishizuka says.