Slater-Pauling behavior and origin of the half-metallicity of the full-Heusler alloys

Abstract

Using the full-potential screened Korringa-Kohn-Rostoker method we study the full-Heusler alloys based on Co, Fe, Rh and Ru. We show that many of these compounds show a half-metallic behavior, however in contrast to the half-Heusler alloys the energy gap in the minority band is extremely small due to states localized only at the Co (Fe, Rh or Ru) sites which are not present in the half-Heusler compounds. The full-Heusler alloys show a Slater-Pauling behavior and the total spin-magnetic moment per unit cell (Mt) scales with the total number of valence electrons (Zt) following the rule: Mt = Zt − 24. We explain why the spin-down band contains exactly 12 electrons using arguments based on the group theory and show that this rule holds also for compounds with less than 24 valence electrons. Finally we discuss the deviations from this rule and the differences compared to the half-Heusler alloys.

The effect of pressure and alloying on half-metallicity of quaternary Heusler compounds CoMnYZ (Z = Al, Ga, and In)

“…Since the half-Heusler alloy NiMnSb was firstly predicted to be a half-metallic ferromagnet (HFM) by utilizing the first principles calculations in 1983 [1], new half-metallic Heusler alloys, which are metallic for one spin direction while semiconducting for the other spin direction, have always received the theoretical and experimental attention due to their potential applications in the fields of magnetic sensors, tunnel junctions and other spintronic devices [2][3][4]. Heusler alloys, with structural formulas of X 2 YZ (with L2 1 structure) and XYZ (with Cl b structure), in which X and Y are transition * E-mail: rahmounemohammed@yahoo.fr metals and Z is a main-group element, are one of the most attractive HM materials, since they can be synthesized easily and their Curie temperatures are high [5][6][7][8][9].…”

Epitaxial Growth of Full-Heusler Alloy Co$_2$MnSi Thin Films on MgO-Buffered MgO Substrates

“…This is because of the half-metallic ferromagnetic nature theoretically predicted for some of these alloys [10], [11] and because of their high Curie temperatures, which are well above room temperature (RT) [12]. We recently reported fully epitaxial magnetic tunnel junctions (MTJs) with a Co-based full-Heusler alloy thin film of either Co Cr Fe Al (CCFA) or Co MnGe as a lower electrode and a MgO tunnel barrier and obtained relatively high tunnel magnetoresistance (TMR) ratios at RT for these epitaxial MTJs (e.g., 42% for CCFA-MTJs at RT) [3], [6], [8].…”

Interface Characterization of Current-Perpendicular-to-Plane Spin Valves Based on Spin Gapless Semiconductor Mn2CoAl

“…In addition, one spin band (majority spin) of HMHA exhibits metallic behavior, while the other spin band (minority spin) displays semiconductor behavior, and such a band structure could generate a high spin polarized current. Therefore, HMHA has been explored as an electrode of CPP-SV to achieve a high magnetoresistance (MR) ratio [5][6][7][8][9][10][11]. Takayashi et al reported a large MR ratio of 74.8% at room temperature (RT) in CPP-SV using Co 2 MnGa 0.…”