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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 4243-4245 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetization, magnetic susceptibility, and neutron diffraction measurements have been made on the alloy series CoAl1−xMnx over a wide range of temperature for 0〈x〈0.4. In this range of concentration the alloys retain the singly ordered B2 (CsCl) structure and neutron diffraction results suggest that the Mn atoms predominantly enter Al sites. However, at concentrations less than x=0.15 about 1% of Mn atoms may possibly enter Co sites with consequent displacement of Co atoms to Al sites. All the alloys show ferromagnetic behavior with Curie temperatures up to 675 K. Evidence for the coexistence of superparamagnetism is found indicating some clusters may not be coupled to the infinite cluster. The superparamagnetism persists to a limited extent above the Curie temperatures for most of the alloys and conventional analysis suggests cluster moments of ∼1000μB for x=0.1 for example. At high temperatures Curie–Weiss behavior is consistent with a moment of ∼0.4μB per formula unit with a composition independent Curie constant suggesting an itinerant origin for the ferromagnetism. Low field (10 Oe or less) magnetization measurements have also been performed for x=0.1 and 0.2. There is a significant difference between zero-field cooled and field-cooled curves at low temperatures indicating a freezing at ∼80 K for x=0.1 and ∼15 K for x=0.2.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5271-5273 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetization and magnetic susceptibility measurements have been made over a wide range of temperature for the alloy series CoAl1−xVx for 0≤x≤0.5. Neutron diffraction measurements have also been made at room temperature using the Rutherford Appleton Laboratory spallation source (ISIS). The observed intensities suggest that for x≤0.25 the structure is the singly ordered B2 (CsCl) structure with the V atoms occupying Al sites. Beyond this concentration a model in which double ordering of the L21 (Heusler) type with the V atoms favoring one of the two equivalent Al sites seems consistent with the results. The magnetization measurements indicate that the series becomes ferromagnetic for x〉∼0.1 with the intrinsic magnetization σ rising to a maximum of ∼50 emu. g−1 at x=0.5 for which the Curie temperature TC is ∼320 K. The inverse susceptibilities are generally linear with temperature and almost independent of concentration for x〉0.2, suggesting an itinerant interpretation. The maximum values of TC and σ reached are less than half those achieved in the corresponding CoAl1−xMnx system but comparable with those seen in the CoAl1−xCrx system. Comparisons with the isoelectronic CoGa system are drawn. The results have relevance to theoretical estimates of impurity moments in CoAl and CoGa.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3241-3243 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The substitution of a 3d transition metal (T) for Al in the equiatomic intermetallic compound FeAl results in the onset of ferromagnetism beyond a certain critical concentration of (T). The system appears magnetically and structurally similar to the equivalent Co(GaT) alloys for which the critical concentration appeared to be related to an average electron concentration parameter. The present paper discusses Cu substitution in FeAl, i.e., the series FeAl1−xCux. It was found using x-ray and neutron diffraction techniques that the alloys remain single phase up to x=0.35 and that the crystallographic order remains B2 throughout. The site occupancy has also been determined and compared with the predictions of theoretical models. Ferromagnetism is observed to occur in the alloys with x〉0.2. For these ferromagnetic alloys the inverse susceptibility against temperature curves (for T〉TC) all have the same slope independent of composition suggesting an interpretation in terms of an itinerant model. This interpretation is also supported by a Rhodes–Wohlfarth plot. A region of superparamagnetism presages the onset of ferromagnetism and from this the size of the magnetic clusters is estimated to be 20–25 A(ring) in radius.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
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