Element specific characterization of heterogeneous magnetism in (Ga,Fe)N films

We employ x-ray spectroscopy to characterize the distribution and magnetism of particular alloy constituents in (Ga,Fe)N films grown by metal organic vapor phase epitaxy. Furthermore, photoelectron microscopy gives direct evidence for the aggregation of Fe ions, leading to the formation of Fe-rich nanoregions adjacent to the samples surface. A sizable x-ray magnetic circular dichroism (XMCD) signal at the Fe L-edges in remanence and at moderate magnetic fields at 300 K links the high temperature ferromagnetism with the Fe(3d) states. The XMCD response at the N K-edge highlights that the N(2p) states carry considerable spin polarization. We conclude that FeN{\delta} nanocrystals, with \delta > 0.25, stabilize the ferromagnetic response of the films.Comment: 4 pages, 3 figures, 1 tabl

Interplay of Chemical Bonding and Magnetism in Fe_4N, Fe_3N, Fe_2N

Using spin density functional theory we have carried out a comparative study of chemical bonding and magnetism in Fe_4N, Fe_3N and Fe_2N. All of these compounds form close packed Fe lattices, while N occupies octahedral interstitial positions. High spin fcc Fe and hypothetical FeN with rock salt structure have been included in our study as reference systems. We find strong, covalent Fe-N bonds as a result of a substantial \sigma-type p-d hybridisation, with some charge transfer to N. Those Fe d orbitals which contribute to the p-d bonds, do no longer participate in the exchange splitting of the Fe d bands. Because of the large exchange fields, the majority spin d bands are always fully occupied, while the minority spin d bands are close to half-filling, thus optimizing the Fe d-d covalent bonding. As a consequence, in good approximation the individual Fe moments decrease in steps of 0.5 \mu_B from fcc iron (2.7 \mu_B) via Fe_4N (2.7 and 1.97 mu_B}), \chem{Fe_3N} (1.99 \mu_B) to \zeta - Fe_2N (1.43 \mu_B).Comment: 16 pages, 15 figure

Structure determination of ζ−Fe2N\mathrm{\zeta-Fe_2N} by neutron and synchrotron powder diffraction

Microcrystalline samples of ζ-Fe2N were prepared from iron powder in a glass apparatus under flowing ammonia. The crystal structure was studied by neutron and high resolution synchrotron powder diffraction at room temperature. ζ-Fe2N crystallizes orthorhombic: space group Pbcn (No. 60), and and seven structural parameters with both sets of data commonly refined; RBragg = 4.2% (neutron), RBragg = 5.6% (synchrotron)

Bestimmung der Luftdichtheit von einzelnen Gebaeudeteilen mit Hilfe der Blower-Door-Methode - DB Hamm

The blower door measuring system consisted of a variable frame with airtight foil and integrated speed-controlled blower, a volume flow meter and differential pressure manometer. It was not possible in all cases to generate sufficient volume flow for achieving the desired pressure gradient, both in the atrium and the building as a whole. In these cases, only the volume flow for a pressure gradient was measured. The curve was approximated using typical curves, and an n_5_0 value was extrapolated which is not a real n_5_0 value but an estimated value based on the values measured for low pressure gradients. Extensive measurements were carried out on different parts of the building.SIGLEAvailable from TIB Hannover: F03B1506 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman