Spin-filter and spin-gapless semiconductors: The case of Heusler compounds

I Galanakis,K Özdoğan,E Şaşıoğlu

doi:10.1063/1.4943761

Abstract

We review our recent first-principles results on the inverse Heusler compounds and the ordered quaternary (also known as LiMgPdSn-type) Heusler compounds. Among these two subfamilies of the full-Heusler compounds, several have been shown to be magnetic semiconductors. Such material can find versatile applications, e.g. as spin-filter materials in magnetic tunnel junctions. Finally, a special case are the spin-gapless semiconductors, where the energy gap at the Fermi level for the one spin-direction is almost vanishing, offering novel functionalities in spintronic/magnetoelectronic devices.

Highlights

We have presented a short review of our recent ab-initio results on two distinct subfamilies of the full-Heusler compounds: (a) the so-called inverse Heusler compounds with the chemical formula X2YZ where X and Y are transition metal atoms with the valence of X being the smallest, and (ii)the ordered quaternary Heusler compounds which have the chemical formula (XX’)YZ where X, X’ and Y are transition metals
Due to the existence of three magnetic sublattices, they present a variety of magnetic orders depending on their chemical composition
These materials can be used in applications, like magnetic tunnel junctions, as spin-filter materials

Summary

INTRODUCTION

The latter compounds are often called half- or semi-Heusler compounds or Heuslers with NiMnSb being the most-known,[10] while the L21 compounds are known as full-Heusler compounds Among both the full and semi Heusler compounds several have been predicted and proved experimentally to present the so-called half-metallic property, i.e. the majority-spin electronic band structure is a usual metallic one while the minority band is semiconducting with a gap at the Fermi level EF, leading to 100% spin polarization of conduction electrons at EF.[11,12,13,14,15] Heusler compounds are particular interesting for applications due to their relative high Curie temperatures and an extensive review on potential applications can be found in Ref. 16.

INVERSE FULL-HEUSLER COMPOUNDS

ORDERED QUATERNARY HEUSLER COMPOUNDS

MAGNETIC SEMICONDUCTORS

SUMMARY AND CONCLUSIONS