Researchers from Tohoku University, University of Tokyo, Australian Nuclear Science and Technology Organization, High Energy Accelerator Research Organization and Comprehensive Research Organization for Science and Society have found that the spin current signal changes direction at a certain magnetic temperature and diminishes at lower temperatures.
Spintronics uses electrons’ intrinsic spin, which is vital to the field, to regulate the flow of the spin degree of freedom, that is, spin currents. Scientists are continually exploring new ways to manage spintronics for future uses. Detecting spin currents is quite complicated and necessitates the use of macroscopic voltage measurement, which examines the entire voltage fluctuations across a material. However, a major stumbling block has been a lack of understanding of how the spin current flows or propagates inside the material.
Using neutron scattering and voltage measurements, the scientists demonstrated that the magnetic properties of the material can predict how a spin current changes with temperature. They also discovered that the spin direction, or magnon polarization, flips at and below this crucial magnetic temperature. This shift in magnon polarization corresponds to the reversal of the spin current, providing information on its propagation direction.
The material tested exhibited magnetic properties with unique gap energies. This shows that spin current carriers are nonexistent below the temperature associated with this gap energy, explaining the observed decrease in the spin current signal at lower temperatures. Surprisingly, the spin current’s temperature dependence exhibits an exponential decrease, echoing the neutron scattering measurements.
The team gained 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.