Interfacial Structure Dependent Spin Mixing Conductance in Cobalt Thin Films

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Understanding spin pumping is crucial for spintronic applications.
• Gilbert damping in magnetic thin films is influenced by interfaces.
• Polycrystalline cobalt thin films exhibit different crystallographic textures based on thickness.

Purpose of the Study:

• To investigate the role of local interface structure in spin pumping.
• To study the enhancement of Gilbert damping in cobalt-based multilayers.
• To correlate crystallographic texture with interfacial spin mixing conductance.

Main Methods:

• Fabrication of polycrystalline cobalt thin-film multilayers with varying thicknesses.
• Overlayer deposition of copper or iridium.
• X-ray diffraction analysis to determine film texture (fcc(111) vs. hcp(0001)).
• Measurement of Gilbert damping and interfacial spin mixing conductance.

Main Results:

• Cobalt films < 6 nm show fcc(111) texture; thicker films (> 6 nm) exhibit hcp(0001) structure.
• Intrinsic damping is thickness-independent for Co > 6 nm.
• Iridium overlayers show higher damping enhancement than copper below 6 nm Co thickness.
• Interfacial spin mixing conductance is significantly enhanced for fcc(111) Co/Ir interfaces compared to hcp(0001) Co interfaces.

Conclusions:

• Local interface structure, specifically crystallographic orientation, plays a critical role in spin pumping efficiency.
• The fcc(111) texture at the cobalt-iridium interface leads to enhanced spin mixing conductance.
• These findings provide insights for designing advanced spintronic materials with tailored interfacial properties.