Ferromagnetism and Electronic Structures of Nonstoichiometric Heusler-Alloy Fe_3-xMn_xSi Epilayers Grown on Ge(111)

TL;DR

This study demonstrates tunable ferromagnetic properties and half-metallic electronic structures in nonstoichiometric Fe_3-xMn_xSi Heusler-alloy epilayers grown on Ge(111), with potential applications in spintronics.

Contribution

It reveals that nonstoichiometric Fe_3-xMn_xSi epilayers maintain ordered structures and exhibit high Curie temperatures, advancing understanding of ferromagnetism in Heusler alloys for spintronic devices.

Findings

Curie temperature exceeds 300 K for x ~ 0.6

Epitaxial layers retain L2_1 order despite nonstoichiometry

Electronic structures become half-metallic for 0.75 < x < 1.5

Abstract

For the study of ferromagnetic materials which are compatible with group-IV semiconductor spintronics, we demonstrate control of the ferromagnetic properties of Heusler-alloys Fe_3-xMn_xSi epitaxially grown on Ge(111) by tuning the Mn composition x. Interestingly, we obtain L2_1-ordered structures even for nonstoichiometric atomic compositions. The Curie temperature of the epilayers with x ~ 0.6 exceeds 300 K. Theoretical calculations indicate that the electronic structures of the nonstoichiometric Fe_3-xMn_xSi alloys become half-metallic for 0.75 < x < 1.5. We discuss the possibility of room-temperature ferromagnetic Fe_3-xMn_xSi/Ge epilayers with high spin polarization.