Combining Spin-Seebeck and Nernst Effects in Aligned MnBi/Bi Composites

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• The spin-Seebeck effect (SSE) involves magnon-electron spin transfer from ferromagnets (FM) to non-magnetic metals (NM) with strong spin-orbit coupling (SOC).
• The Nernst effect is a bulk thermoelectric phenomenon observed in homogeneous magnetic or non-magnetic materials.
• Both effects share similar experimental geometries, suggesting potential for synergistic interactions.

Purpose of the Study:

• To investigate the additive nature of the spin-Seebeck effect and Nernst effect in a new FM/NM composite material.
• To explore FM/NM composites synthesized via in-field annealing for enhanced transverse thermopower.
• To analyze microstructural, magnetic, and transport properties for evidence of combined SSE and Nernst effects.

Main Methods:

• Fabrication of MnBi (FM) and Bi (NM) composites using in-field annealing to create aligned MnBi needles within a Bi matrix.
• Characterization of material microstructures, magnetic properties, and electrical transport behavior.
• Measurement of transverse thermopower to detect contributions from both SSE and Nernst effects.

Main Results:

• Successful synthesis of MnBi/Bi composites with aligned FM needles in an NM matrix.
• Evidence of additive signals from the spin-Seebeck effect and Nernst effect in samples with lower MnBi concentrations.
• Demonstration that the combined SSE and Nernst effect can enhance transverse thermopower.

Conclusions:

• The spin-Seebeck effect and Nernst effect are additive in specific FM/NM composite architectures.
• In-field annealing is a viable method for creating materials with combined spin-thermoelectric properties.
• This work presents a new strategy for designing and studying advanced spin-thermoelectric composite materials.