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  • 1
    Digitale Medien
    Digitale Medien
    Growth of giant magnetoresistance spin valves using Pb and Au as surfactants (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 5183-5191 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have investigated the use of Pb and Au as surfactants in an attempt to achieve smoother and sharper interfaces in three types of giant magnetoresistance (GMR) spin valve multilayers: symmetric spin valves, bottom spin valves, and top spin valves. The coupling fields are reduced by a factor of 10 for symmetric and bottom spin valves and by a factor of 3 for top spin valves, presumably by suppressing roughness and interdiffusion at the Co/Cu/Co interfaces, when ∼1 monolayer of Pb is deposited in the early stages of spin valve growth. The Pb has a strong tendency to float out or segregate to the surface during deposition of the spin valve leaving the GMR largely unaltered. Au is almost as effective as Pb, however the Au tends to be left behind in the spin valve, and the GMR is reduced slightly. Attempts to use Hg as a surfactant were unsuccessful. The coupling field increased, and the GMR decreased sharply. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.363460
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  • 2
    Digitale Medien
    Digitale Medien
    The trade-off between large magnetoresistance and small coercivity in symmetric spin valves (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 8603-8606 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have investigated the use of various alloys as substitutes for pure Co in the center film of symmetric spin valves of the type NiO/Co/Cu/Co/Cu/Co/NiO. The aim of this work is to identify magnetic materials that exhibit smaller coercivities than pure Co for the center or "valve'' film but which retain much of the giant magnetoresistance associated with a pure Co film. The materials investigated include Co95Fe5, Co90Fe10, Ni80Fe20, Co86Fe10.5Ni3.5, and Co85B15. It appears that each of these alloys scatters electrons more strongly than does pure Co as they cross the center film. This scattering degrades the dual spin-valve effect, which is the primary advantage of the symmetric spin valve. As a result, a tradeoff exists between large GMR and small coercivity when using these materials. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.362457
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  • 3
    Digitale Medien
    Digitale Medien
    Optimizing the giant magnetoresistance of symmetric and bottom spin valves (invited) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5277-5281 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have attempted to optimize the values of the giant magnetoresistance in symmetric spin valves of the type NiO/Co/Cu/Co/Cu/Co/NiO (achieving 23.4%) and in bottom spin valves of the type Co/Cu/Co/NiO (achieving 17.0%), the largest values ever reported for such structures. The key elements in this achievement are improved vacuum conditions and careful attention to the film thicknesses. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.361352
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  • 4
    Digitale Medien
    Digitale Medien
    Heat capacity measurements of NiO/CoO superlattices (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. 5919-5919 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present heat capacity measurements of NiO/CoO superlattices grown by reactive sputtering. Neutron diffraction studies of similar superlattices have shown antiferromagnetic ordering through several bilayers despite the short-range nature of the spin interaction in the constituent materials. Specific heat measurements were made using a unique thin film microcalorimeter capable of measuring the heat capacity of thin films from 1.5 K to well above room temperature. We examine the effect of exchange coupling at the interfaces by varying the thickness of the bilayers. For thin bilayers (26 A(ring)), we observe a single broad heat capacity peak similar to a Ni0.5Co0.5O alloy. This peak is at a temperature which corresponds to the superlattice magnetic blocking temperature. For thicker bilayers ((approximately-greater-than)50 A(ring)), two broad maxima occur which approach the individual Néel temperatures of CoO and NiO with increasing bilayer thickness. The ordering temperature of the NiO layers is more suppressed than expected, indicating a more pronounced size effect compared to the CoO layers. The magnetic entropy S=R(ln 3+ln 2)/2 for the superlattices, within the uncertainties of the measurement, is conserved. We compare the temperature dependences of the specific heats to various models. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.361838
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  • 5
    Digitale Medien
    Digitale Medien
    Magnetoresistance values exceeding 21% in symmetric spin valves (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 273-277 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report values of the giant magnetoresistance (GMR) effect exceeding 21% in symmetric spin valves, the highest values ever reported for such structures. The key elements in this achievement are the use of a Co/Cu/Co/Cu/Co multilayer in which the center Co layer is substantially thicker than the outer Co layers and the use of the antiferromagnetic insulator NiO at the top and bottom to pin the adjacent Co layers magnetically. The relative Co layer thicknesses suggest that some specular scattering of conduction electrons may occur at the metal/insulator interfaces and may enhance the GMR. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.360692
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  • 6
    Digitale Medien
    Digitale Medien
    Heat capacity measurements of antiferromagnetic CoO/NiCoO superlattices (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. 6292-6292 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present heat capacity and magnetic measurements of antiferromagnetic (AFM) CoO/Ni0.5Co0.5O superlattices grown by reactive sputtering. X-ray data verify the structure and the high quality of the superlattice. Neutron-diffraction studies of similar superlattices have shown AFM ordering through several bilayers despite the short-range nature of the spin interaction in the constituent materials. We have recently developed a unique thin film microcalorimeter capable of measuring thin films from 1.5 K to well above room temperature, permitting specific heat measurements on these superlattices for the first time. Magnetic measurements were made by coupling the superlattices to a 30 nm Ni81Fe19 overlayer and measuring the temperature dependence of the exchange anisotropy field. We examine the effect of exchange coupling at the interfaces by varying the thickness of the bilayers and their constituents. When the layers of the CoO/Ni0.5Co0.5O superlattice are thin, we observe a single broad heat capacity peak at a temperature between the Néel temperatures of bulk CoO and Ni0.5Co0.5O. This peak is at a temperature that corresponds to the superlattice magnetic blocking temperature, the temperature at which the exchange field goes to zero. For thicker layers, we observe the disappearance of the superlattice peak, and the emergence of two broad peaks close to the individual Néel temperatures of CoO and Ni0.5Co0.5O. We compare the temperature dependence of the specific heat of the superlattices to various models.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.358311
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  • 7
    Digitale Medien
    Digitale Medien
    Lanthanum-substituted Y-Ba-Cu-O superconductors synthesized at elevated oxygen pressures (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 715-717 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Lanthanum substitution in the Y-Ba-Cu-O system at elevated P(O2) results in superconducting compositions which throw interesting light on the effects of nonisovalent substitution in a Y-Ba-Cu-O system. Like Ca substitution, La substitution also shifts the phase formation boundary between 123, 247, and 124 phases to higher P(O2), and stabilizes a tetragonal 123 structure at moderately elevated P(O2). However, in contrast with Ca substitution, Tc decreases continuously and rapidly with increasing La content. This can be only partly explained by a decrease of the hole concentration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.104257
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  • 8
    Digitale Medien
    Digitale Medien
    The uptake of macromolecular materials in the hindgut of viviparous rockfish embryos (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 46 (1995), S. 0 
    Details
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Regions of the gut of near-term embryos and new-born larvae of the viviparous rockfish Sebastes taczanowskii were examined histologically and immunohistochemically in order to ascertain whether they possessed the potential to absorb intact macromolecules. Compared with the hindgut of larvae 24 h after parturition, that of near-term embryos (stage 31) was found to be markedly hypertrophied and to react positively when tested for the presence of eosinophilic materials and with antibodies raised against extracts of the rockfish yolk (ab.a-E). In addition, near-term embryos incubated in Ringer solution containing 1% bovine serum albumin appeared to accumulate the protein within the epithelium of the hindgut. Furthermore, as confirmed by immunodiffusion analysis, the ovarian fluid contained materials which reacted positively to ab.a-E. These results suggest that ingestion of intact macromolecules occurs during the late embryonic stages and that the yolk-like substances detected within the hindgut epithelium of such embryos may be derived from the bathing ovarian fluid.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1095-8649.1995.tb05989.x
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  • 9
    Digitale Medien
    Digitale Medien
    Rhythmic changes in testicular activity with lunar cycle in the forktail rabbitfish (2003)
    Oxford, UK : Blackwell Science Ltd
    Journal of fish biology 62 (2003), S. 0 
    Details
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Testosterone, 11-ketotestosterone and 17α ,20β-dihydroxy-4-pregnen-3-one in the forktail rabbitfish Siganus argenteus peaked around the full moon and the last quarter moon, respectively. Since changes in these hormones were correlated with histological change in the testis, the present study provided conclusive evidence for importance of the lunar periodicity in the reproductive activity of the forktail rabbitfish.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1095-8649.2003.00036.x
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  • 10
    Digitale Medien
    Digitale Medien
    Oxygen consumption rates of tilapia in fresh water, sea water, and hypersaline sea water (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 51 (1997), S. 0 
    Details
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Whole animal oxygen consumption rates and plasma constituents were determined in the tilapia O. mossambicus, acclimated for 1 month in fresh water, sea water, and 1·6 × sea water. Oxygen consumption rates for the three water salinities were: 177·2 ± 16·86, 78·6 ± 2·32, and 195·4 ± 15·39 mg O2 kg−1 h−1 (means ± 1 s.e.), respectively. Plasma prolactin (tPRL188) concentration was significantly lower in 1·6 × sea water compared to fresh and sea water. There were no significant differences among mean plasma cortisol concentration and lysozyme activity. Ventilation was significantly higher in fish in sea water compared to the fish in fresh and 1·6 × sea water. The lowest oxygen consumption rates were found in fish acclimated to sea water. That salinity is probably closest to the brackish waters from which they were captured in the wild, and this agreement likely reflects the selection for optimal morphological and physiological characteristics to live in that environment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1095-8649.1997.tb01528.x
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