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  • 1995-1999  (4)
  • 1985-1989  (2)
  • 1970-1974  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Goldanskii-Karyagin effect versus preferred orientations (texture) (1973)
    Springer
    Applied physics 1 (1973), S. 93-102 
    Details
    ISSN: 1432-0630
    Keywords: Mössbauer spectroscopy ; Goldanskii-Karyagin effect ; Lattice vibrational anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract There are two main contributions influencing the relative line intensities in a hyperfine pattern of a polycrystalline material: 1) Lattice vibrational anisotropy-Goldanskii-Karyagin effect (GKE) and 2) preferred orientation of the crystallites (texture). We present the results of experiments and computer calculations of the line-intensity ratios for various orientation distributions. The two competing effects are hard to distinguish from an experimental point of view, and this evaluation should enable one to appreciate the magnitude of their respective contributions. A variety of textures is selected and discussed: For instance, the interesting case where the GKE and the texture produce the same effect on the relative line intensities. Generally speaking, it seems that in many qualitative discussions of quadrupole line asymmetries the influence of texture is underestimated, especially for small deviations from randomness. Conversely, the asymmetry in the spectra is often explained by making the ad hoc assumption of a GKE without realizing that this would require an unrealistic lattice vibration anisotropy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00887072
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    An autonomous programmable system for Mössbauer spectroscopy, accessed by a PC program (1997)
    Springer
    Hyperfine interactions 110 (1997), S. 135-141 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A low cost, stand alone microprocessed equipment for data acquisition and driver control, designed under the requirements of Mössbauer spectroscopy is described. It has a functional mode as pulse analyzer (PHA) and a second mode as a multichannel analyzer (MCA) while it generates waveforms -- triangular, sawtooth and sinusoidal -- between 2 and 40 Hz, buffered up to a capacity of 750 mA for velocity transducer (DRIVER) management, with PID signal synthesizer and error minimization circuits. Its resolution is variable, between 2 and 1024 channels. The system has CMOS technology of integration, Z-80--74HC, with a 4.9152 MHz crystal time based; its dead time is of 0.61 μs and its minimum dwell time is of 32 μs. Data are continuously kept in memory and can be transferred, under a managing program request, via RS-232c protocol at 9600 BAUD -- to a PC computer for its analysis and display. The program written for a PC is able to distinguish up to 8 different spectrometers by means of an identity number assigned to each unit. Therefore, the serial input may be multiplexed in order to attend all the systems, that can work simultaneously.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012650710935
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Study of ferrofluids by Mössbauer spectroscopy (1998)
    Springer
    Hyperfine interactions 113 (1998), S. 507-515 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The parameters of the log‐normal size distribution of a MnFe2O4 ferrofluid powder sample have been determined by X‐ray diffraction. The mean blocking temperature was determined from the maximum of Xi . Mössbauer spectra at 4.2–300 K are interpreted by a new simple theory of superparamagnetism and taking a reduction of the internal magnetic field for small particles, a size dependence of the anisotropy constant, the size distribution and collective excitations into account.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012616909485
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Simple theory of superparamagnetism and spin-tunneling in Mössbauer spectroscopy (1997)
    Springer
    Hyperfine interactions 110 (1997), S. 127-134 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The magnetic relaxation of isolated small (〈 100 Å) monodomain magnetic particles is due to superparamagnetic relaxation (predominant at high temperatures) and eventually quantum tunneling of the magnetic moment (at low temperatures). The superparamagnetic relaxation process can be formally described by an (multiple phonon absorption and emission) Orbach process with an anisotropy Hamiltonian due to crystalline or form anisotropy \widehatIon = S2 z and a usual dynamical spin-Hamiltonian for the spin--phonon interaction. From this Mössbauer spectra can be calculated using ab-initio or stochastic methods. Phonon-assisted tunneling and its influence on Mössbauer spectra are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012654811844
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Electronic structure and spin relaxation of Fe(III) in LiNbO3 (1986)
    Springer
    Hyperfine interactions 28 (1986), S. 785-788 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Crystal field parameter have been determined from EPR spectra (77K) of LiNbO3∶Fe(III). Anomalous line shapes are described phenomenologically and saturation studies are compared with calculations using a second order dynamic spin-hamiltonian H′. Mössbauer spectra of LiNbO3∶Fe(III) have been interpreted by means of simulations using Liouville superoperators including a static fine-and a hyperfine spin-hamiltonian and H′. Calculations have been performed using an effective spin of 1/2, the supermatrix with dimension 288 and a reduced formalism (supermatrix with dimension 96).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02061563
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetic properties of Y(Fe0.95Mn0.05)2 compound (1999)
    Springer
    Hyperfine interactions 122 (1999), S. 209-215 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Mössbauer spectroscopy, magnetization and X-ray diffrraction measurements of the ternary compound Y(Fe0.95Mn0.05)2 prepared by melting were performed in order to investigate the effect of the substitution of Mn on the magnetic properties of YFe2. The experimental results show change of the lattice parameter. The magnetization and the Curie temperature decrease with substitution of Fe by Mn.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012618327851
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Mössbauer relaxation spectra of LiNbO3: Fe(III) (1988)
    Springer
    Hyperfine interactions 42 (1988), S. 1067-1070 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Mössbauer spectra of LiNbO3: Fe(III)-monocrystals were measured in zero external magnetic field (5mK to 673K). They all show typical lineshapes due to relaxation effects. Below 77K temperature independent and above 77K a temperature-dependent relaxation is observable. In spectra measured in external magnetic fields relaxation effects occur only above 77K. We present least square fits of spectra measured at 300K and external magnetic fields using symmetry invariant reservoir spectral densities. The applied numerical formalism takes the complete electronuclear manifold of57Fe(III) into account. We discuss the problems concerning the interpretation of zero field spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02395575
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    Paper (German National Licenses)
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