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  • Articles: DFG German National Licenses  (17)
  • 1990-1994  (17)
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  • Articles: DFG German National Licenses  (17)
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Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Exchange coupling, interface structure, and perpendicular magnetic anisotropy in Tb/Fe multilayers (abstract) : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6293-6293 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Tb/Fe multilayer films are known to show perpendicular magnetic anisotropy (PMA), which is interesting for potential applications in magneto-optical data storage. We demonstrate by using 57Fe Mössbauer probe layers and x-ray diffraction that part of the Tb-deposited-on-Fe (Tb/Fe) interface remains chemically sharp and crystalline bcc Fe. This part is associated with an unexpectedly strong antiferromagnetic exchange coupling of the Fe to the Tb layers. We find by using both conventional and circularly polarized radiation that part of the interface and core bcc Fe but none of the amorphous Fe is strongly coupled to Tb. This behavior is qualitatively explained by a structural model including regions with a sharp Tb/bcc-Fe interface, where PMA originates from Tb ions that experience the broken symmetry of the crystal electric field at the interface. The extrapolated isomer shift at T=0 K of the amorphous phase located at the Fe-deposited-on-Tb (Fe/Tb) interface was found to be different from that of the amorphous phase located at the Tb/Fe interface, suggesting a different amorphous structure at both interfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358312
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Interface alloying and magnetic properties of Fe/Rh multilayers : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6528-6530 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Rh(20 A(ring))/57Fe(tFe) multilayers with Fe thicknesses tFe of 2, 5, 10, and 15 A(ring) prepared by alternate evaporation in UHV have been investigated by x-ray diffraction (XRD), Mössbauer spectroscopy, and SQUID magnetometry. First- and second-order superstructure Bragg peaks (but no higher-order peaks) in small-angle XRD patterns suggest some compositional modulation. Mössbauer spectra taken at 4.2 K are characterized by a distribution P(Bhf) of hyperfine fields Bhf. Peaks observed in the P(Bhf) curves near 17 and 35 T are assigned to an fcc-R(underbar)h(underbar)Fe interface alloy (∼7–24 at. % Fe) with spin-glasslike properties and to a disordered ferromagnetic bcc-F(underbar)e(underbar)Rh alloy (∼96 at. % Fe), respectively. The magnetic transition temperature of the fcc alloy was found to be 23 and 45 K for tFe=2 and 5 A(ring), respectively, and Bhf follows a T3/2 law. For tFe=2 A(ring), spin-glasslike behavior was observed by magnetometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358213
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  • 3
    Electronic Resource
    Electronic Resource
    Correlation of magneto-volume effects and local properties of the Fe2Ti-laves phase (abstract) : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6912-6912 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magneto-volume effects have been calculated and shown to exist in Fe2Ti alloys. Since Mössbauer spectroscopy provides insight into local magnetic properties we have performed such measurements in the temperature range 4.2 K〈T〈800 in Bext=0 and ≠0 on Fe2+xTi1−x powder samples with x=−0.05 to +0.1. The spectra of Fe2Ti at 4.2 K show two subspectra, one belonging to the antiferromagnetically coupled 6h sites, and the other one to the paramagnetic 2a sites, in agreement with Ref. . A detailed analysis shows that the electric field gradient of the 6h sites changes in sign and value when going from the antiferromagnetic to the paramagnetic state at 310 K. Moreover, the isomer shift values of the two sites are found to be different at 4.2 K, while they are equal above 310 K. Both changes suggest a change in the local electronic band structure between the paramagnetic and antiferromagnetic states. An increase of the linewidth is observable in the temperature region of 200 K〈T〈310 K that could be caused by a distribution of hyperfine fields on the 6h sites or by spin fluctuations during the lifetime of the excited state of the Mössbauer nucleus. For x(approximately-greater-than)0 and 4.2 K, an additional magnetically split subspectrum appears that is associated with 6h sites and neighboring Fe antisite atoms. For x〈0 the spectra are similar to those of Fe2Ti.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358113
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  • 4
    Electronic Resource
    Electronic Resource
    The variation of anisotropy and magnetization orientation with temperature in Tb/Fe multilayers : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6907-6909 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: On the basis of the co-effect of the crystal field with a random distribution and the molecular field and using anisotropic static magnetic couplings, we calculated the polar angle aitch-theta of the magnetic moment in 15×(26 A(ring) Tb/40 A(ring) Fe)+40 A(ring) Fe multilayers as function of temperature from 4.2 to 300 K, which agrees well with experiment. As a result of the calculation, the width of interface mixing layer and the coefficient of the crystal field are determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352430
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetic properties of Fe/Tb multilayers : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6206-6208 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Multilayered Fe/Tb samples were prepared under ultrahigh vacuum conditions (p〈10−9 mbar) on kapton substrates. A total of four different samples were prepared. Three of them correspond to a series where the Tb thickness is constant at 26 A(ring) and Fe varies from 10 to 30 A(ring). The fourth one is the first of a new series where Tb is 7 A(ring) thick and Fe 40 A(ring). The samples were investigated by means of SQUID magnetometry and Mössbauer spectroscopy. All samples show perpendicular magnetic anisotropy at low temperature (4.2 K), but only two of them are able to show it at room temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349996
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  • 6
    Electronic Resource
    Electronic Resource
    The spin texture in Fe/Tb multilayers (1992)
    Springer
    Hyperfine interactions 68 (1992), S. 409-412 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Fe/Tb multilayers (ML) have been prepared in UHV. The layer thickness for Fe was varied from 10 to 80 Å with Tb-layer thicknesses of 3.5, 7, 14 and 26 Å. Different substrate temperatures Ts between Ts=130 K and RT have been used. The magnetic spin texture was studied by57Fe-Mössbauer spectroscopy from T=4.2 K to 670 K. The ferrimagnetic coupling between Fe and Tb moments was observed by Mössbauer studies in external fields up to 5 T.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02396522
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  • 7
    Electronic Resource
    Electronic Resource
    On the Mössbauer site assignment in YBa2(Cu1−xFex)3Oy (1990)
    Springer
    Hyperfine interactions 55 (1990), S. 1229-1242 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The assignment of the four57Fe Mössbauer sites which are observed in Fe-substituted YBa2Cu3Oy is presented. We present a systematic study of highly-controlled samples with low Fe-concentration over the whole oxygen concentration range. Two sites are found to dominate in the limit of high oxidation (y→7), indentified as Fe4+ on the two crystallographic Cu sites: Cu(1) and Cu(2). These are replaced at lower oxidation (y→6) by two others, which we identify with Fe3+ on these same two sites. Consistency is found with the sign of the electric field gradient (EFG), the asymmetry parameter η and the isomer shiftI S for this model. The magnetic structure in the limit y→6 shows changes in the antiferromagnetic (AF) structure dependent on iron concentration. Mössbauer and spin-echo NMR results show a change in the Cu(2) AF layer sequence at low temperatures, without any magnetic moments on the Cu(1) chain sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02397153
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  • 8
    Electronic Resource
    Electronic Resource
    Bi, Sn and Sb valence states in highT c (Bi, Pb/Sn, Sb)2Sr2Ca2Cu3Oy (1990)
    Springer
    Hyperfine interactions 55 (1990), S. 1243-1248 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The valence of Bi and its substituents Sn and Sb are investigated in the high temperature superconductor (Bi0.8X0.15Sb0.05)2Sr2Ca2Cu3Oy (often denoted 2223) where X=Pb or Sn. Pb and Sn are isoelectronic with the valence states 2+ and 4+; Bi and Sb are as well with valence states 3+ and 5+. The valence state of Sn and Sb has been obtained from Mössbauer spectroscopy: they exist in the high charge states 4+ and 5+ respectively. Sn, Sb, and presumably Pb, take on the high valence state, and so furnish electrons to the conduction band. This is probably the reason why, although the (Pb, Sb)-doping aids in stabilizing the 2223 crystal structure, it is detremental to the electronic properties which lead to the superconducting phase. The valence state of Bi has been studied using X-ray photoelectron spectroscopy (XPS). These results show clearly that the Bi-based superconductor has a metal-like density of states at the Fermi level, and that the valence in the (Pb, Sb)-doped compounds is less than 3. This very surprising change in valence will have a profound effect on the superconducting properties, and is probably associated with the high valent states of Pb, Sn and Sb.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02397154
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  • 9
    Electronic Resource
    Electronic Resource
    CEMS-study of the interface in Fe/Cr multilayer systems (1990)
    Springer
    Hyperfine interactions 57 (1990), S. 1941-1947 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The magnetic hyperfine (hf.) fields at the Fe/Cr interface were analyzed in epitaxial Fe/Cr thin film structures of (100)- and (110)-orientation with monolayer resolution by means of in-situ57Fe Conversion Electron Mössbauer Spectroscopy (CEMS). The hf. field (300 K) in the 1st Fe-monolayer (ML) at the interface has been found to be strongly reduced to 22.0/20.9 T for (110)-/(100)-orientation, whereas the 2nd and 3rd ML reveal a slightly increased hf. field of 33.7 T as compared with the Fe-bulk value of 33.4 T. The temperature dependence of the hf. field at the interface shows aT 3/2 spin wave law. The spin wave parameters are enlarged with respect to the bulk value indicating a reduced exchange interaction. A discontinuity in theT 3/2-dependence is interpreted by the onset of magnetic order (Néel-temperature) of the Cr layers adjoining the57Fe probe layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405746
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  • 10
    Electronic Resource
    Electronic Resource
    CEMS and DCEMS investigations of Al-implanted iron (1994)
    Springer
    Hyperfine interactions 92 (1994), S. 1367-1372 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract α-Fe surfaces were implanted with a nominal dose of 5×1017 Al ions/cm2 at 50 keV and a current density of about 3.7 μA/cm2. Samples of different shapes and thicknesses have been used in order to test the influence of heat flow from specimen to target holder during implantation. Integral and energy differential (“depth-selective”)57Fe conversion electron Mössbauer spectroscopy (CEMS and DCEMS) were employed. The spectra indicated a magnetic phase characterised by a broad hyperfine field distributionP(B hf), a non-magnetic phase, and α-Fe. The relative intensity of the non-magnetic phase was enhanced if the thermal contact during implantation became worse. An energy dependence of DCEM spectra in the L-electron range was observed. Model calculations using L-electron weight functions and experimental concentration profiles obtained by secondary neutral mass spectroscopy (SNMS) yielded fair agreement between calculated and experimental phase signals. The results demonstrate that the non-magnetic Fe-Al alloy phase with high Al concentration is located closer to the surface than the magnetic alloy phase, which extends to much larger depth than expected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02065780
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