Weak temperature dependence of orbital Hall angle in Ta/Ni bilayers

Area of Science:

• Spintronics
• Condensed Matter Physics
• Materials Science

Background:

• Characterizing temperature dependence of spin Hall angle (SHA) is key to understanding spin Hall effect (SHE).
• Experimental data on orbital Hall effect (OHE) under varying temperatures are limited.
• The effective charge-to-spin conversion efficiency (θH) combines SHA and orbital Hall angle (OHA).

Purpose of the Study:

• To systematically investigate the temperature dependence of effective charge-to-spin conversion efficiency (θH) in Ta/Ni and Ta/CoFeB bilayers.
• To determine the dominant contribution of OHE versus SHE in Ta/Ni.
• To understand the temperature dependence of OHA in Ta/Ni.

Main Methods:

• Fabrication of Ta/Ni and Ta/CoFeB bilayers.
• Systematic measurement of effective charge-to-spin conversion efficiency (θH) from 10 K to 300 K.
• Comparative analysis of Ta/Ni and Ta/CoFeB samples to isolate OHE contributions.

Main Results:

• The θH in Ta/Ni remained positive across the temperature range, indicating OHE dominance over SHE.
• Ta/CoFeB samples showed negative θH, consistent with SHA of Ta and negligible OHE.
• Both Ta/Ni and Ta/CoFeB exhibited similar increasing trends in θH as temperature decreased.
• The similar trends suggest a weak temperature dependence of OHA in Ta/Ni.

Conclusions:

• Orbital Hall effect plays a dominant role in Ta/Ni bilayers.
• The orbital Hall angle in Ta/Ni demonstrates weak temperature dependence.
• These findings enhance the understanding of OHE and support potential applications in orbitronics.