Monitoring surface resonances on Co2MnSi(100) by spin-resolved photoelectron spectroscopy

TL;DR

This study investigates the surface resonance in Co2MnSi(100) using spin-resolved photoelectron spectroscopy, revealing a highly spin-polarized surface state that extends into the bulk, crucial for spintronics applications.

Contribution

It provides a detailed experimental and theoretical analysis of the surface resonance in Co2MnSi(100), highlighting its bulk-like behavior and strong coupling to the bulk states.

Findings

Observed 93% spin polarization at room temperature.

Identified a surface resonance extending over six atomic layers.

Confirmed the resonance's bulk-like nature through spectroscopy and calculations.

Abstract

The magnitude of the spin polarization at the Fermi level of ferromagnetic materials at room temperature is a key property for spintronics. Investigating the Heusler compound Co$_2$MnSi a value of 93$\%$ for the spin polarization has been observed at room temperature, where the high spin polarization is related to a stable surface resonance in the majority band extending deep into the bulk. In particular, we identified in our spectroscopical analysis that this surface resonance is embedded in the bulk continuum with a strong coupling to the majority bulk states. The resonance behaves very bulk-like, as it extends over the first six atomic layers of the corresponding (001)-surface. Our study includes experimental investigations, where the bulk electronic structure as well as surface-related features have been investigated using spin-resolved photoelectron spectroscopy (SR-UPS) and for a larger probing depth spin-integrated high energy x-ray photoemission spectroscopy (HAXPES). The results are interpreted in comparison with first-principles band structure and photoemission calculations which consider all relativistic, surface and high-energy effects properly.