Slater-Pauling Behavior of the Half-Ferromagnetic Full-Heusler Alloys

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. These full-Heusler compounds show a Slater-Pauling behavior and the total spin-magnetic moment per unit cell (M_t) scales with the total number of valence electrons (Z_t) following the rule: M_t=Z_t-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.Comment: 10 pages, 8 figures, revised figure 3, new text adde

Half-metallicity and Slater-Pauling behavior in the ferromagnetic Heusler alloys

Introductory chapter for the book "Halfmetallic Alloys - Fundamentals and Applications" to be published in the series Springer Lecture Notes on Physics, P. H. Dederichs and I. Galanakis (eds). It contains a review of the theoretical work on the half-metallic Heusler alloys.Comment: Introductory chapter for the book "Halfmetallic Alloys - Fundamentals and Applications" to be published in the series Springer Lecture Notes on Physics, P. H. Dederichs and I. Galanakis (eds

An experimental study of the magneto-optical properties of ferromagnetic alloys

Summary in DutchApplied SciencesApplied Science

MAGNETIC PROPERTIES AND KERR ROTATION IN AMORPHOUS Ce-Fe AND Pr-Fe ALLOYS

Several amorphous Ce-Fe and Pr-Fe alloys were prepared by means of vapour-deposition and their magnetic properties were studied. The Ce1-xFex alloys are ferromagnetic with magnetic ordering temperatures below room temperature, even for Fe concentrations as high as 90 at% Fe. In the Pr1-xFex alloys magnetic ordering appears to be more complex than ferromagnetic. Magnetic ordering temperatures are in excess of room temperature. At low temperatures the intrinsic coercive force is appreciable. At higher temperature it decreases strongly according to the relation IHc-1αT. Due to the low ordering temperature the room temperature Kerr rotation is very low in Ce1-xFex. Much higher values are observed in Pr1-xFex. Here the concentration dependence of the Kerr rotation gives rise to a maximum near 80 at% Fe

Magnetic and Magneto-Optical Properties of NiMnSb1-xSnx Compounds in Relation to their Electronic Band Structure

We have determined the magnetic and magneto-optical properties of pseudoternaries of the type NiMnSb1-xSnx. These materials were found to have the cubic MgAgAs structure (C1b) for concentrations where x ≤ 0.7. Lattice constants, saturation moments, Curie temperatures and magneto-optical Kerr rotations (0.5-4.5 eV) were found to vary smoothly with x, which makes it possible to derive by extrapolation values of all these physical constants for the fictitious compound NiMnSn. Calculations of the electronic band structure were made for NiMnSn and NiMnSb0.75Sn0.25. These calculations and those presented earlier for NiMnSb were used to analyse the magnetic and magneto-optical properties of the compounds NiMnSb1-xSnx.

New Class of Materials: Half-Metallic Ferromagnets

The band structure of Mn-based Heusler alloys of the C1b crystal structure (MgAgAs type) has been calculated with the augmented-spherical-wave method. Some of these magnetic compounds show unusual electronic properties. The majority-spin electrons are metallic, whereas the minority-spin electrons are semiconducting.

Magnetic and Crystallographic Properties of Several C1b Type Heusler Compounds

The compounds NiMnSb and IrMnGa were studied by neutron diffraction. The former compound has the cubic C1b crystal structure with an ideal site occupancy of the atoms. Below 750 K the compound is ferromagnetically ordered. The magnetic moments are confined to the Mn atoms (4.0μB/Mn). The compound IrMnGa has a crystal structure related to the C1b type but characterized by a high atomic disorder. Results of magnetic measurements are presented for NiMnSb, CuMnSb and IrMnGa. The results of these measurements are in accord with the occurrence of high atomic ordering in the first two compounds but point to high atomic disorder in the latter material. Total energies and Mn moments derived from band-structure calculations are presented for three different types of site occupancies in NiMnSb. The lowest total energy as well as the correct value for the Mn moment correspond to the site occupancy found by means of the neutron diffraction.

Optical properties of some half-metallic ferromagnets

In this Letter we report ellipsometry measurements on polycrystalline samples of NiMnSb and PtMnSb at room temperature under ultra-high vacuum conditions. From these measurements the optical constants of the two materials were determined in the energy range 0.5-5.3 eV. The measured optical conductivities are in reasonable agreement with the optical conductivities calculated from the band structures. The band gap for the minority-spin direction is clearly observed and can be brought into agreement with the band-structure calculations by consideration of spin-orbit splitting.