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  • 1
    Electronic Resource
    Electronic Resource
    Mössbauer effect study of face-centered-cubic-like Fe on Cu(001) (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4265-4272 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial face-centered-cubic (fcc)-like Fe films have been investigated in situ in ultrahigh vacuum by 57Fe conversion-electron Mössbauer spectroscopy (CEMS). A broad distribution of hyperfine magnetic fields, P(Bhf), with an extrapolated most-probable field of 32(2) T at magnetic saturation has been observed in ∼3 monolayers (ML) thick films grown at ∼90 or 300 K, and in ∼7 ML thick films grown at ∼90 K. Such films are in a ferromagnetic high-spin state. Their local structure is characterized by an electric quadrupole interaction, eQVZZ/4, of +0.114±0.05 mm/s from which we infer an anisotropically expanded fcc (fct-like) structure with c/a≈1.06. Approximately 5–7 ML thick films grown at 300 K are observed to be in a low-spin antiferromagnetic state below TN∼70 K, and are fcc (c/a=1) above TN. Site-selective CEM spectra taken on such films provide direct evidence for a magnetically "live'' surface layer. The fcc→bcc transformation occurring in 35 ML thick films deposited at 300 K was observed to be incomplete. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361795
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  • 2
    Electronic Resource
    Electronic Resource
    Mössbauer-effect study of face-centered-cubic-like Fe on Cu(001) (invited) (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5582-5582 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: More than 30 years ago, Weiss has postulated the existence of two different magnetic fcc-Fe states [high-spin (HS)/high atomic volume or low-spin (LS)/low atomic volume] in order to explain the Invar effect in fcc-Fe alloys. Such metastable states may be stabilized by epitaxial growth of ultrathin Fe films on Cu(001) under suitable conditions which depend on film thickness and growth temperature. In situ conversion-electron Mössbauer spectroscopy, combined with low-energy electron diffraction, reflection high-energy electron diffraction, and Auger electron spectroscopy, on ∼3- and ∼7-ML-thick 57Fe films grown in ultrahigh vacuum at 300 K reveals a thickness-dependent transition from a HS ferromagnetic (FM) state with an anisotropically expanded fcc (fct-like) structure (c/a(approximately-greater-than)1) to a LS antiferromagnetic (AFM) isotropic fcc state. In contrast, the stability of the HS fct-like phase is extended to at least 7 ML in films grown at low T (90 K) and annealed to 300 K. The HS-FM phase in 7 ML films is rather stable against annealing up to 500 K; annealing at 570 K leads to a HS–LS transformation which is correlated with abrupt surface segregation of Cu. By placing 2-ML-thick isotopically enriched 57Fe-probe layers into a 300 K grown natural Fe film of 7 ML total thickness we could obtain a magnetic depth profile along the film-normal direction: while the LS-AFM state (with TN∼70 K) was found at the film center and a paramagnetic Fe–Cu alloy at the Fe/Cu interface, Fe surface atoms were observed to be in a HS-FM state with a noncubic atomic environment. Only today can we begin to understand the complex behavior of fcc-Fe/Cu(001). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362247
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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Magnetism and structure of Dy/Fe multilayers studied by 57Fe and 161Dy Mössbauer spectroscopy (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4503-4511 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dy(48 A(ring))/Fe(40 A(ring)) multilayers were investigated by 57Fe and 161Dy Mössbauer spectroscopy in zero external field between 4.2 and 300 K. The 57Fe spectra could be analyzed in terms of a pure bcc-Fe contribution and an intermixed interface contribution. The latter is assigned to an amorphous Dy1−xFex interface alloy with an estimated most-probable composition x≈0.78. The bcc-Fe phase shows a broad spin-reorientation transition from a preferentially in-plane-oriented Fe-spin direction near 300 K to a more out-of-plane-oriented spin texture at 4.3 K characterized by an average misalignment angle of ∼52° relative to the sample-plane normal. The value of the average 161Dy hyperfine field at 4.2 K (583.0 T) is slightly larger than the value of bulk Dy metal, but is smaller than those of Dy–Fe intermetallics. The average orientation of Dy moments which was found to be random at 4.2 K may be the reason for the misalignment of Fe magnetic moments at low temperature. The magnetic ordering temperatures of the Dy layers were determined by superconducting quantum interference device magnetometry to be TC=110±15 K and TN=200±20 K, the latter value being in agreement with that estimated from 161Dy spectra. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363431
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  • 7
    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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  • 8
    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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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    The sign of the EFG in semiconducting and grain-oriented high-T c YBa2 (Cu1−x 57Fe x )3O y by Mössbauer spectroscopy (1989)
    Springer
    Hyperfine interactions 50 (1989), S. 541-541 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02407689
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