In this study, we used the thermally driven spin current to investigate the spin frustrations and spin fluctuations in spin-glass (SG) Cu1−xMnx alloys. Tuning the Cu1−xMnx composition results in a transition of the alloys from the SG state to the antiferromagnetic state; these states have different spin-freezing temperatures (Tf). For each alloy composition, we obtained a temperature-dependent inverse spin Hall voltage with a peak at Tp. We demonstrated that Tp has a strong correlation with Tf because of almost identical composition dependence. Crucially, we provided direct evidence that the strongest spin fluctuation occurs at a temperature considerably higher than the magnetic critical temperature, which could be attributed to the long and complex spin-freezing process. The proposed approach utilizing the spin current is not only a promising alternative in studying the spin-freezing transition for SG but also may enable energy-efficient spintronic applications using SG materials.

 

This work is published in Physical Review B (101, 104413 (2020)).