2013/09/25 by E. Şaşıoğlu, Ersoy Sasioglu, I. Galanakis +3
Materials Science · Physics and Astronomy · #Heusler alloys: electronic and magnetic properties #Magnetic Properties and Applications #Magnetic properties of thin films #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.88.134402
published as Phys. Rev. B 88, 134402 (2013) · 11 pages, 3 figures, 4 tables; accepted for publication in Phys Rev B
arxiv created 2013/09/25 · openalex publication_date 2013/10/02 · arxiv updated 2015/06/17 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Correlation effects play an important role in the electronic structure of half-metallic (HM) magnets. In particular, they give rise to nonquasiparticle states above (or below) the Fermi energy at finite temperatures that reduce the spin polarization and, as a consequence, the efficiency of spintronics devices. Employing the constrained random-phase approximation (cRPA) within the full-potential linearized augmented-plane-wave (FLAPW) method using maximally localized Wannier functions, we calculate the strength of the effective on-site Coulomb interaction (Hubbard U and Hund exchange J) between localized electrons in different classes of HM magnets considering: (i) sp-electron ferromagnets in rock-salt structure, (ii) zinc-blende 3d binary ferromagnets, as well as (iii) ferromagnetic and ferrimagnetic semi- and full-Heusler compounds. For HM sp-electron ferromagnets, the calculated Hubbard U parameters are between 2.7 and 3.9 eV, while for transition-metal-based HM compounds, they lie between 1.7 and 3.8 eV, being smallest for MnAs (Mn-3d orbitals) and largest for Cr2CoGa (Co-3d orbitals). For the HM full-Heusler compounds, the Hubbard U parameters are comparable to the ones in elementary 3d transition metals, while for semi-Heusler compounds, they are slightly smaller. We show that the increase of the Hubbard U with structural complexity, i.e., from MnAs to Cr2CoGa, stems from the screening of the p electrons of the nonmagnetic sp atoms. The p-electron screening turns out to be more efficient for MnAs than for Cr2CoGa. The calculated Hubbard U parameters for CrAs, NiMnSb, and Co2MnSi are about two times smaller than previous estimates based on the constrained local-density approximation (cLDA) method. Furthermore, the width of the correlated d or p bands of the studied compounds is usually smaller than the calculated Hubbard U parameters. Thus these HM magnets should be classified as weakly correlated materials.