First-Principles Study of Ferromagnetic Heusler Alloys: An Overview

Abstract

A particularly attractive class of materials for spintronic applications is represented by half-metals (i.e., materials showing carriers at the Fermi level 100% spin-polarized), among which ferromagnetic Heusler alloys occupy a prominent position. Here, we present a review of first-principles calculations based on the density functional theory, focusing in particular on i) several mechanisms that are predicted to destroy half-metallicity and ii) magneto-optical properties such as the Kerr rotation. We show that defect-induced states at the Fermi level in Co-based Heusler-alloys such as Co₂MnSican drastically reduce the degree of spin-polarization, pointing to the necessity of keeping point-defects under control during experimental growth. In the context of spin-injection into mainstream semiconductors, interface states are also predicted to be induced by the junction between a full-Heusler and GaAs. A careful analysis of the magneto-optical Kerr effect is performed for several Co-based full-Heusler alloys. Although the size of the Kerr rotation is found to be of the order of 0.5° and therefore not technologically appealing, we show that first-principles calculations can be efficiently used as a tool to predict novel half-metals with large Kerr angles.