Longitudinal spin Seebeck coefficient: heat flux vs. temperature difference method.

Area of Science:

• Condensed Matter Physics
• Spintronics
• Materials Science

Background:

• The longitudinal spin Seebeck effect (LSSE) coefficient measurement suffers from significant uncertainty and poor experimental reproducibility.
• Variations in experimental conditions, particularly thermal contact resistance, are primary causes for this lack of reproducibility.

Purpose of the Study:

• To analyze and compare two distinct methods for determining the LSSE coefficient: the temperature difference method and the heat flux method.
• To identify the key factors contributing to uncertainty in LSSE measurements and propose a more reliable approach.

Main Methods:

• Performed LSSE experiments across multiple laboratories using different experimental setups.
• Employed both the temperature difference method and the heat flux method for coefficient determination.
• Analyzed the impact of thermal contact resistance on measurement reproducibility.

Main Results:

• LSSE experiments demonstrated that scaling the LSSE voltage to heat flux, rather than temperature difference, substantially reduces uncertainty.
• The heat flux method yielded consistent LSSE device characteristics ((1.143 ± 0.007) × 10⁻⁷ Vm/W and (1.101 ± 0.015) × 10⁻⁷ Vm/W) across different setups.
• The temperature difference method showed considerable variation in results ((2.313 ± 0.017) × 10⁻⁷ V/K and (4.956 ± 0.005) × 10⁻⁷ V/K).

Conclusions:

• Thermal contact resistance is a critical factor affecting LSSE measurement reproducibility.
• The heat flux method offers a more robust and reliable approach for determining the LSSE coefficient compared to the temperature difference method.
• Employing the heat flux method can significantly mitigate systematic errors in LSSE characterization.