Thermal and Coherent Spin Pumping by Noncollinear Antiferromagnets

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Antiferromagnets offer potential for spintronic applications due to their unique magnetic properties.
• Noncollinear antiferromagnets, in particular, remain less explored despite their fundamental physics interest.
• Understanding spin dynamics in these materials is crucial for advancing spintronic device functionalities.

Purpose of the Study:

• To theoretically investigate the thermal and coherent spin pumping phenomena in noncollinear antiferromagnet/normal metal bilayers.
• To elucidate the nature of spin current polarization and spin mixing conductance in these systems.
• To address the sign problem associated with the antiferromagnetic spin Seebeck effect.

Main Methods:

• Formulation of theoretical models for thermal and coherent spin pumping.
• Analysis of spin current polarization vector components.
• Characterization of spin mixing conductance as a tensor dependent on material and interface properties.

Main Results:

• The spin current polarization was found to possess components along both the Néel vector and the net magnetic moment.
• Spin mixing conductance was identified as a tensor, with its elements influenced by the degree of noncollinearity and the interface spin configuration.
• Interface effects were proposed as the explanation for the controversial sign problem in the antiferromagnetic spin Seebeck effect.

Conclusions:

• The study provides a theoretical framework for understanding spin pumping in noncollinear antiferromagnets.
• The findings highlight the significant role of interface properties in dictating spin dynamics and spin Seebeck effect behavior.
• Interface engineering is suggested as a viable strategy to enhance spin pumping efficiency in antiferromagnetic spintronic devices.