Realisation of magnetically and atomically abrupt half-metal/semiconductor interface: Co₂FeSi_0.5Al_0.5/Ge(111)

Area of Science:

• Materials Science
• Condensed Matter Physics
• Spintronics

Background:

• Half-metal/semiconductor interfaces are essential for advanced spintronic applications.
• Achieving atomically sharp interfaces with high spin polarization is critical for efficient spin injection.

Purpose of the Study:

• To investigate the formation and properties of interfaces between the half-metallic Heusler alloy Co2FeSi0.5Al0.5 and Germanium (Ge).
• To determine if these interfaces maintain high spin polarization for spintronic device applications.

Main Methods:

• Fabrication of thin films of Co2FeSi0.5Al0.5 on Ge(111).
• Characterization using atomic resolution energy dispersive X-ray spectroscopy, polarized neutron reflectivity, X-ray reflectivity, and aberration-corrected electron microscopy.
• First-principles calculations to analyze interface structure, magnetic properties, and spin polarization.

Main Results:

• A structurally abrupt interface between Co2FeSi0.5Al0.5 and Ge(111) was successfully formed.
• Limited Ge outdiffusion into the Co2FeSi0.5Al0.5 film occurred within a 1 nm region, specifically along Fe-Si/Al atomic planes.
• First-principles calculations confirmed that this outdiffusion did not affect the magnetic moment at the interface.
• Experimental and theoretical methods confirmed the interface is magnetically and structurally abrupt.
• The interface, terminated by Co-Ge bonds, preserves high spin polarization.

Conclusions:

• The Co2FeSi0.5Al0.5/Ge interface is atomically sharp, magnetically abrupt, and preserves high spin polarization.
• This experimentally realized structure serves as a model for studying spin injection from half-metals into semiconductors.
• The findings pave the way for developing efficient hybrid spintronic devices.