ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Springer  (3)
  • 1995-1999  (3)
Collection
Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Muons and muonium in Zn‐spinels (1997)
    Springer
    Hyperfine interactions 106 (1997), S. 187-192 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have studied the magnetic spinel (Zn)[Fe2]O4 (T_ N\approx10.5\ K) and the non‐magnetic spinels (Zn)[Al2]O4, (Zn)[Ga2]O4, (Zn)[ZnTi]O4 and (Zn)[ZnSn]O4 , both with surface and decay channel muons. In (Zn)[Fe2]O4 the relaxation rate increases monotonically from room temperature down, typical for a paramagnet. Around 30 K, an additional, stronger damped signal appears which is the signature of short‐range ordered (SRO) regions. Their total volume fraction increases drastically towards T_ N (reaching 75%) and astonishingly, continues to be present also below T_ N where the rest of the material has become long‐range ordered. Longitudinal field μSR proves the SRO to be dynamic. In (Zn)[Al2]O4 and (Zn)[Ga2]O4 muon depolarization is caused solely by 27Al or 69,71Ga nuclear dipoles. In the inverse spinel (Zn)[ZnTi]O4, half of the implanted muons depolarize rapidly (\lambda\approx 3μs-1 at room temperature). This, together with repolarization behavior in longitudinal fields indicates that the muon in (Zn)[ZnTi]O4 undergoes a chemical reaction after implantation forming muonium. The fact that no such muonium formation occurred in another inverse spinel ( (Zn)[ZnSn]O4) means that the presence of muonium is not connected to the inverse structure but rather due to the presence of Ti which offers two d‐electrons to participate in the chemical bonding. Additional evidence for d‐electron participation is provided by 67Zn‐Mössbauer data which indicate unusual electron densities at the 67Zn nuclei only in (Zn)[ZnTi]O4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012650110142
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Dynamic short-range order observed in the (Zn)[Fe2]O4 spinel by neutron diffraction, μSR, and Mössbauer experiments (1996)
    Springer
    Hyperfine interactions 97-98 (1996), S. 373-386 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using neutron diffraction (ND), muon-spin rotation/relaxation (μSR), and57Fe-Mössbauer spectroscopy (MS) we have investigated magnetic properties of the normal spinel (Zn)[Fe2]O4. In compounds which are slowly cooled from 1200°C to room temperature inversion is below detection limits. AtT N = 10.5 K the spinel exhibits long-range antiferromagnetic order (LRO). The transition as seen in thermal-scan spectra by MS is very sharp. However, ND andμSR experiments show that already at temperatures of ∼ 10T N a short-range antiferromagnetic ordering (SRO) develops which extends through ∼70% of the sample volume just aboveT N . BelowT N SRO and LRO coexist. At 4.2 K still ∼25% of the sample is short-range ordered. The regions over which the SRO extends have a size of ∼ 3 nm. Their fluctuation rates are in the GHz range. Modern ab initio cluster calculations successfully describe the magnetic hyperfine fields as well as the electric field gradient (EFG) tensor at the Fe sites. Covalency of the Fe-O and Zn-O bonds is important. The physical origin of the regions exhibiting SRO, however, remains unresolved at this point.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02150186
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    67Zn-Mössbauer study of nanostructured ZnO (1995)
    Springer
    Hyperfine interactions 95 (1995), S. 247-255 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using the 93.31 keV Mössbauer transition in67Zn we have investigated hyperfine interactions and lattice-dynamic effects of nanostructured hexagonal (wurtzite) ZnO. The nanocrystals with particle sizes between 3 and 30 ran were produced by a reactive-gas sublimation method and were subsequently compacted into solid bodies under external pressure. The nanocrystalline materials were used as sources in Mössbauer emission experiments. A drastic increase of the asymmetry parameter was found fromη=0 (single crystal) toη≈0.5 (nanostructured material). Our theoretical Hartree-Fock cluster calculations show that displacements of the Zn atoms off the hexagonal symmetry axis as small as 0.005 Å can lead to such enhancedη parameters. The Lamb-Mössbauer factorf drastically drops when the particle size is reduced below ∼ 10 nm. Two lattice-dynamic models are discussed which successfully describe this behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02146317
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...