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  • 1
    Electronic Resource
    Electronic Resource
    Temperature dependence of the magnetic excitations in ordered and disordered Fe72Pt28 : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6072-6074 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have performed inelastic neutron scattering measurements of the long-wavelength spin wave excitations of both ordered and disordered Fe72Pt28 single crystals below their critical temperatures, TC=510 and 375 K, respectively. The spin waves followed the expected E=Dq2 dependence, and the temperature-dependent spin stiffness D decreased as (T/TC)5/2, as expected for an isotropic ferromagnet. The extrapolated zero-temperature spin stiffness was D=98(4) meV A(ring)2 and 107(1) meV A(ring)2 for the disordered and ordered alloy, respectively. These values are significantly higher than the zero-temperature stiffness as determined by magnetization measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355461
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Transition temperature depression in quench condensed Zn-Mn dilute alloy films (1973)
    Springer
    The European physical journal 259 (1973), S. 135-144 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The depression of the superconducting transition temperature has been investigated foruhv quench condensed Zn-Mn alloy films, containing 5–50 ppm Mn. Within accuracy limits the result for the initial depressiondT c /dc=285± 30 K/at% is in agreement with the bulk material value of 305 K/at%, supporting the equivalence between quench condensed films and bulk material alloys. A detailed analysis of the data within the framework of the Zittartz-Müller-Hartmann theory shows, that for the “Kondo-system” Zn-Mn (withT k /T c0 ≈ 1 andS=3/2) the thin film results follow the theoreticalT c depression curve better than the bulk material values. This is due to the early onset of impurity-impurity interactions in the bulk alloys, which are reduced in quenched films because of reduced mean free path of the conduction electrons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01392843
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of atomic order on [110] phonon softening [4] and displacive phase transition in Invar alloys (1999)
    Springer
    The European physical journal 10 (1999), S. 641-648 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 63.20.Dj Phonon states and bands, normal modes, and phonon dispersion - 64.70.Kb Solid-solid transitions - 65.40.+g Heat capacities of solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The acoustic phonon dispersions of two Invar crystals , one ordered with the ( ) structure, the other disordered fcc, have been investigated between 3.4 K and 470 K by inelastic and elastic neutron scattering. For the ordered crystal, pronounced softening of the whole phonon branch is observed on cooling below the Curie temperature. Particularly strong phonon softening at the M-point zone boundary of the structure leads to a displacive, antiferrodistortive phase transition at low temperatures. For the disordered crystal, much weaker softening of the phonons is observed and restricted to the region near the Brillouin zone center, where increasing elastic scattering with decreasing temperature indicates the growth of local tetragonal strain. This strain is considered as a typical precursor of the transformation to bct martensite. Specific heat measurements, performed at low temperatures on both crystals confirm the neutron scattering results and reveal considerable enhancement of the low energy phonon density of states in the ordered crystal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050896
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  • 4
    Electronic Resource
    Electronic Resource
    Kondo effect and impurity interactions in the resistivity of diluteZnMn alloys (1977)
    Springer
    Journal of low temperature physics 29 (1977), S. 411-429 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The electrical resistivity of diluteZnMn alloys (c=1.7–2400 ppm Mn) has been investigated in the temperature range from 0.05 to 14 K. For the most dilute sample, single-impurity Kondo behavior is found, well described by the Hamann formula withT K=0.9 K,S=3/2. ForT〈50 mK, aT 2 law with θ R =0.3 K is expected. In the dilute limit the Kondo slope is −(1/c)d(Δρ)/d(logT)=3.7±0.2 µΩ-cm/at % dec. In the more highly concentrated alloys, the slope decreases with increasing c and the lnT-like variation of the Kondo resistivity roughly terminates near a temperatureT W(c),T W being related to the average Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction strength between the Mn impurities. For 20 ppm ≤c ≤ 1000 ppm, the resistivity slightly decreases at low temperatures and a broad resistivity maximum is observed atT m (c), withT m ∝c 0.7. ForT 2〈T m, the resistivity dependence is linear inT, and for the most concentrated alloy aT 3/2 orT 2 dependence is measured at the lowest temperatures attainable. The investigation of the transition temperatureT c (c) to superconductivity ofZnMn results in a critical concentrationc cr=18 ppm Mn. The concentration dependence ofT c below 0.3 K suggests the presence of the Kondo effect, although impurity interactions may also influenceT c in this temperature range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00661537
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  • 5
    Electronic Resource
    Electronic Resource
    Moment-volume instabilities in alloys with compositions around the C14 laves phase (1998)
    Springer
    The European physical journal 5 (1998), S. 361-365 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.25.+z Spin arrangements in magnetically ordered materials - 75.30.Kz Magnetic phase boundaries - 75.10.Lp Band and itinerant models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We measured the thermal expansion and the specific heat of TixFe100-x alloys with x = 30.5, 32.5 and 35, all with hexagonal C14 laves phase structure (MgZn2) like TiFe2, and determine the temperature dependence of the magnetic contributions to the thermal expansion and the specific heat cmag. For fixed composition and c mag ( T ) show the same type of behavior, demonstrating that both anomalies are of the same microscopic nature. They originate from moment-volume fluctuations (antiferromagnetic Invar-effect) as a comparison with total energy calculations as a function of atomic volume and moment for TiFe2 reveals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050454
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  • 6
    Electronic Resource
    Electronic Resource
    Reverse resistance anomaly and negative magnetoresistance of diluteY: Gd andSc: Gd (1980)
    Springer
    The European physical journal 38 (1980), S. 235-242 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A logarithmical decrease in the resistivity below 10 K has been observed for 200 to 5,000 ppm Gd in Y and Sc. The decrease scales with the Gd concentration. The results are in line with previously published data forLu: Gd and LaAl2: Gd, they are discussed in terms of a ferromagnetic (J〉0) Kondoeffect. The scaling parameterT K , and the extracted effective change interactionJ eff are compared with other experimental results. In addition the negative magnetoresistance (the freezing out of spin-disorder scattering) has been measured up to 50 kG. Possible interference of potential and exchange scattering may have been observed in the magnetoresistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01315662
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  • 7
    Electronic Resource
    Electronic Resource
    phonon dispersion and martensitic phase transition in ordered alloys (1999)
    Springer
    The European physical journal 11 (1999), S. 75-81 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 63.20.Dj Phonon states and bands, normal modes, and phonon dispersion - 81.30.Kf Martensitic transformations - 61.12.-q Neutron diffraction and scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: In a previous neutron scattering study, we had observed that the TA phonon softening in L12-ordered ferromagnetic Fe72Pt28 Invar is pronounced at the zone boundary M-point and leads to an antiferrodistortive phase transition at low temperatures. Here, we report on similar neutron scattering investigations on two ordered crystals with higher Fe content to investigate the relation between the TA phonon softening and the martensitic transformation, which occurs in Fe-rich ordered Fe-Pt. We find that the TA phonon softening, especially at the M-point zone boundary, does not depend on the composition of the investigated crystals. In Fe74.5Pt25.5, however, the antiferrodistortive phase transition temperature is enhanced due to tetragonal strain preceding the martensitic transition. In Fe77Pt23 a precursor driven premartensitic phase transition is not observed. The structure of the martensite is, however, influenced by the soft mode lattice instability of the austenite. This would explain the origin of structural details found previously for Fe3Pt thermoelastic martensite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050918
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