Cracking the code on spin currents

The field of spintronics has a range of advantages for conventional electronics. These include reduction of power consumption, high-speed operation, non-volatility and the potential for new functionalities. Spintronics exploits the intrinsic spin of electrons and fundamental to the field is controlling spin currents, otherwise known as the flows of the spin degree of freedom. Researchers are looking at ways to create, remove and control them for future applications.

Detecting spin currents requires the use of macroscopic voltage measurement, which looks at the overall voltage changes across a material. However, there is a lack of understanding of how this spin current actually moves or propagates within the material itself. Researchers from Tohoku University have now demonstrated that the magnetic properties of the material can predict how a spin current changes with temperature. The researchers found that the spin current signal changes direction at a specific magnetic temperature and decreases at low temperatures. The spin direction, or magnon polarisation, also flips both above and below this critical magnetic temperature. This change in magnon polarisation correlates with the spin current’s reversal, shedding light on its propagation direction.

The material studied also displayed magnetic behaviours with distinct gap energies. This suggests that below the temperature linked to this gap energy, the spin current carriers are absent, leading to the observed decrease in the spin current signal at lower temperatures. The spin current’s temperature dependence follows an exponential decay, mirroring the neutron scattering results.

Yusuke Nambu, an associate professor at Tohoku University, said the research findings underscore the significance of understanding microscopic details in spintronics research. “By clarifying the magnetic behaviours and their temperature variations, we can gain a comprehensive understanding of spin currents in insulating magnets, paving the way for predicting spin currents more accurately and potentially developing advanced materials with enhanced performance,” Nambu said.

Image credit: iStock.com/Henvry