Recently, a research team led by Prof. QU Zhe from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, in collaboration with Prof. LIU Enke from the Institute of Physics of the Chinese Academy of Sciences, found a new way to control the magnetic reversal in a special material called Co3Sn2S2, a Weyl semimetal.
"This discovery could help switch the magnetization of devices that rely on magnetic properties," said Prof. QU, "such as hard drives and spin-based technologies."
The results were published in Materials Today Physics.
Co3Sn2S2 is a magnetic Weyl semimetal with a unique structure, where its magnetic properties are linked to its topological features. The exchange bias (EB) effect, important for stability in magnetic devices, has been observed in this material, but the exact mechanisms behind it are still unclear.
In this study, researchers found that by adjusting the maximum external magnetic field (Hmax) and thermal history, they could control the material' s magnetic reversal. When Hmax was high enough, the material' s coercive fields became symmetric, and the EB-like behavior disappeared. The researchers proposed that local magnetic states play a key role in the tunable magnetic reversals: below certain flipping fields, these states help form reverse magnetic domains, lowering the coercive field. When Hmax exceeds a critical value, these states align with the magnetization direction, no longer affecting the reversal process.
This discovery offers a new explanation for the asymmetric hysteresis loop in Co3Sn2S2, different from the usual EB effect. "by adjusting the maximum external magnetic field, we can control the material’s magnetic reversal and its magnetic-topological properties, effectively tuning the symmetry of the hysteresis loop," said Dr. ZENG Qingqi, a member of the team.
Figure (a–d) Tunable asymmetric Hall loops at 5 K (magnetic histories are shown in insets). (e) Symmetric loops under high enough external magnetic field. (f) Sketch of the influence of positively aligned local magnetic state to magnetic reversals. (Image by ZENG Qingqi)
