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  • 1
    Electronic Resource
    Electronic Resource
    The magnetocaloric effect: The role of magnetic anisotropy : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6507-6509 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In a ferromagnet, the magnetic entropy change induced by the application of a magnetic field is greatest in the temperature regime near the Curie point. In the paramagnetic temperature regime, the magnitude of the magnetocaloric effect is expected to rise monotonically with the size of the individual moments that make up the material. The magnetic properties of such materials are relevant to devices employing magnetic refrigeration. One aspect of the problem, namely the impact of uniaxial magnetic anisotropy on the magnetocaloric effect, is explored. The results of Monte Carlo simulations for classical Heisenberg ferromagnets on a fcc lattice with anisotropy are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352596
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic viscosity in Ni/Cu compositionally modulated alloys (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4904-4906 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The existence of a magnetic aftereffect (magnetic viscosity) in Ni/Cu multilayered alloys was established using a vibrating sample magnetometer at room temperature and at 86 K. It was shown that the effect is strongly dependent on the step field H2 (i.e., the value the field is reduced to after the magnetic moment has been aligned in high field) and exhibits a maximum relaxation rate for values of H2 around the reverse coercive field −Hc. Aftereffect behavior of this type has been observed in other materials, although most often for systems composed of superparamagnetic particles, where the relaxation freezes out at low temperatures. In contrast, the relaxation in the CMA was shown to be enhanced at 86 K over its value at room temperature. New measurements over a wider temperature range show that the enhancement in this sample reaches a maximum near 120 K, but below that temperature the relaxation does freeze out. The temperature of maximum enhancement varies from sample to sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344726
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  • 3
    Electronic Resource
    Electronic Resource
    Cohesion and promotion energies in the transition metals: Implications of the local-density approximation : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5688-5690 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The accuracy of the local-density (LDA) or local-spin-density (LSDA) approximations when applied to transition metals is of great concern. Estimates of the cohesive energy compare the total energy of the solid with that of the free atom. This involves chosing the reference state of the free atom which, as a rule, will not be the free atom's ground state in LDA or LSDA. Comparing one reference state versus another, e.g., the dn−1s vs dn−2s2 for a transition metal, corresponds to calculating an s-d promotion energy Δ, which may be compared with experiment. Gunnarsson and Jones (GJ) [Phys. Rev. B 31, 7588 (1985)] found for the 3d row that the calculated Δ displayed systematic errors which they attributed to a difference in error within the LSDA in the treatment of the coupling of the outer-core electrons with the d versus non-d valence electrons. This study has been extended to relativistic calculations for the 3d, 4d, and 5d rows and for other promotions. The situation is more complicated than suggested by GJ, and its implications for cohesive energy estimates will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347912
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  • 4
    Electronic Resource
    Electronic Resource
    Oral mucosal keratinocytes express RANTES and ICAM-1, but not interleukin-8, in oral lichen planus and oral lichenoid reactions induced by amalgam fillings (2003)
    Oxford, UK : Blackwell Science Ltd
    Clinical and experimental dermatology 28 (2003), S. 0 
    Details
    ISSN: 1365-2230
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Oral lichen planus (OLP) is a chronic inflammatory disease of the oral mucosa characterized by a band-like accumulation of lymphocytes in the connective tissue adjacent to the basement membrane as well as intraepithelially. Amalgam fillings can induce oral lichenoid reactions (OLR) that are similar to OLP. The adhesion molecule ICAM-1 and the chemokines interleukin-8 and RANTES all play central roles in leucocyte trafficking. The aim of this study was to investigate the possible role of these molecules in the migration of leucocytes into the oral mucosa in OLP and OLR. Standard immunoperoxidase techniques were used to visualize the expression of ICAM-1, RANTES and interleukin-8 in frozen biopsy sections. ICAM-1 was expressed by endothelial cells, but not by keratinocytes, in normal oral mucosa. ICAM-1 was expressed by keratinocytes in 11 of 12 biopsies of OLP and in six of seven biopsies of OLR. In all of these cases ICAM-1 was also expressed by endothelial cells and leucocytes. Although not present in normal oral mucosa, RANTES was expressed by keratinocytes in 21 of 24 biopsies of OLP and in seven of seven cases of OLR. Interleukin-8 was not detected in any of the samples. The expression of ICAM-1 and RANTES by epithelial keratinocytes in the oral mucosa in OLP and OLR could be a key inflammatory mechanism in these diseases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2230.2003.01158.x
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of nitrogen on the properties of hard magnets : 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. 6044-6046 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The enhancement of magnetic properties of RE-TM hard magnet materials, such as RE2Fe17, upon nitriding is studied using the Wigner–Seitz (Voronoi) construct. In analogy with other RE-TM nitrides, it is concluded that nitrogen has a strong preference to occupy the octahedral 9e site in the 2:17 compounds, to the exclusion of the other proposed sites. Additional materials are suggested as candidates for nitriding on the basis of the availability of such an octahedral site. The site preference and its effect on the magnetism in RE2Fe17 is discussed in relation to the Wigner–Seitz cell of the atoms. The magnetic moments on the iron are shown to be correlated with the WS cell volumes, and this dependence differs from that associated with αFe.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358360
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  • 6
    Electronic Resource
    Electronic Resource
    Monte Carlo simulations of the magnetocaloric effect in superferromagnetic clusters having uniaxial magnetic anisotropy : 38th Annual Conference On Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5493-5495 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic entropy change, ΔS (hence the heating or cooling) of ferromagnetically coupled magnetic clusters induced by an application of a magnetic field is substantial and occurs over a broad temperature range. This behavior contrasts with a ferromagnetic material, where larger entropy changes can be obtained, but only over small temperature ranges close to the Curie point. Monte Carlo simulations have been carried out to obtain ΔS when the spins are subjected to uniaxial anisotropy fields. While previous calculations for interacting spins showed increases in the Curie temperature and enhancements of ΔS in the vicinity of the Curie point with increasing anisotropy, the present results for interacting clusters show similar increases in the temperature of ΔS peaks accompanied by decreases in the peak values of ΔS. These results show that the flattening of the ΔS peaks, which make superferromagnetic materials valuable for magnetic refrigeration is assisted by the presence of uniaxial anisotropy. Some effects on ΔS of placing the spins on fixed BCC, FCC, and sc lattices are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355667
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  • 7
    Electronic Resource
    Electronic Resource
    Disclinations, crystal fields, and easy axes of magnetization in the hard magnets (abstract) : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5630-5630 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: There is a need for increased insight into the origins of the easy axes of magnetization of the transition metal-rare earth hard magnets. These systems form in Frank Kasper or closely related crystalline structures. David Nelson has pointed out1 that these topologically close packed phases are threaded with disclination lines. The principal chains among these lines, as they pass through rare-earth sites, appear to define the orientations of the crystal fields at these sites and, in turn, the low-temperature easy axes of magnetization. The currently available experimental data are shown to be in almost perfect accord with this definition of easy axes. Using these ideas, predictions are made for systems and structures for which magnetization anisotropy data have yet to be obtained. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364622
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  • 8
    Electronic Resource
    Electronic Resource
    Disclinations: The magnetism and the magnetic anisotropies of the rare-earth–3d transition-metal hard magnets (invited) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3136-3138 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An important class of hard magnets, involving rare earth and 3d transition metals and sometimes metalloids, includes Nd2Fe14B and Nd2Fe17. We have noted a correlation between the local site magnetism in these two compounds and whether those sites lie on nets of so-called major ligand lines or disclinations, i.e., bond lines shared by six common nearest neighbors. We have proposed that a criterion for choosing candidate alloys with strong 3d moments is the occurrence of such disclination nets, and using this criterion, have listed several structures having 3d sites with this characteristic. We have also rationalized the crystal field anisotropies as relating to the orientation of the major ligand lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340866
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  • 9
    Electronic Resource
    Electronic Resource
    Where are the iron atoms and iron moments in RFEmAl12−n? A Wigner-Seitz analysis (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 4246-4248 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ternary compounds RFenAl12−n (n=4,5,6; ThMn12 structure) form an extensive family of alloys having complicated magnetic structures, with the rare earths (R) and Fe ordering at different temperatures. This magnetic ordering has been inferred from magnetization, Mössbauer and neutron diffraction measurements. X-ray results are in disagreement with the magnetic measurements as to which sites are occuped by the Fe, and it is not clear at which of the sites iron has the largest magnetic moment. Recently, we have suggested that the occurrence of a substantial magnetic moment at an atomic site in certain magnetic systems can be related to the occurrence of −72° disclination lines connection atoms on this site. These disclinations are bond lines joining two near-neighbor atoms which have six nearest neighbors and can be recognized by a sixfold face appearing on the Wigner-Seitz polyhedra of the two atoms. The Wigner-Seitz construction and its use in the analysis of this and related problems is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338488
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  • 10
    Electronic Resource
    Electronic Resource
    Magnetic aftereffect in textured Ni/Cu compositionally modulated alloys (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3223-3223 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The existence of a magnetic aftereffect ("magnetic viscosity'') in textured Ni/Cu multilayered alloys was established1 using a vibrating sample magnetometer at room temperature and at 86 K. It was shown that the effect is strongly dependent on the step field, H2 (i.e., the value the field is reduced to after the magnetic moment has been aligned in high field), and exhibits a maximum relaxation rate for values of H2 around the reverse coercive field, Hc. Aftereffect behavior of this type has been observed in other materials, though most often for systems composed of superparamagnetic particles, where the relaxation freezes out at low temperatures. In contrast, the relaxation is enhanced at low temperature in the present situation. Several questions remain open from this earlier work. Among these are: is the effect a property of a thin Ni film or is it attributable to the compositional modulation of the alloy?; what is the exact form of the time decay and what is the mechanism that causes this effect? In order to resolve some of these issues the magnetic aftereffect has been measured in more detail and for longer periods of time at both temperatures (room and 86 K) in a new set of [111]-textured, layered Cu/Ni alloys of varying thicknesses. The slab thickness of the Ni, dNi, was varied between 6 and 30 A(ring), and the ratio dNi/(dNi+dCu) between 0.1 and 0.8.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340848
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