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Título:
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Magnetotransport properties of NiFe-Ag granular alloys: origin of the thermal behavior
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Autor/a:
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Badia Pascual, Ferran; Batlle, X.; Labarta, A.; Watson, M. L.; Johnston, A. B.; Chapman, J. N.
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Notas:
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The effect of the temperature and magnetic field on the giant magnetoresistivity ~GMR! of two
FeNi–Ag granular alloys of composition Fe11.4Ni6.4Ag82.2 and Fe7.6Ni16.4Ag76.0 is discussed. Both
samples were prepared by rf magnetron sputtering. Parts of them were rapidly annealed at 600, 650,
and 750 °C. All samples displayed giant magnetoresistivity which decays from its maximum value
with a Tm behavior, with m'0.8– 0.9, suggesting that the decrease in the maximum
magnetoresistivity is due to the reduction in the particle magnetization associated with the spin wave
excitation, which is a different mechanism to the electron-magnon interaction responsible for the
T dependence of GMR in magnetic multilayers. Magnetoresistivity r M decreases with temperature
sharing essentially the same temperature decrease as the square of the macroscopic magnetization
M in the whole magnetic field range studied, which is due to the reduction in the particle
magnetization and to superparamagnetic effects. The effect of the width of the particle size
distribution and interparticle interactions on the linear relation r M vs M2 are discussed. Care should
be taken when representing r M /r(T,H50) vs (M/Ms)2 because the strong temperature-dependent
slope shown in these plots is mainly due to the temperature dependence of both the resistivity
r(T,H50) and Ms , and it is not an intrinsic T dependence of GMR in granular alloys.
Experimental results suggest that in granular materials, magnetoresistivity is dominated by magnetic
moments at the surface of the particles, which also play a very important role in the demagnetization
processes, and small magnetic particles.
Financial support of both the Spanish CICYT through the MAT94-1024-CO2-02 Project and the Catalan CIRIT through the GRQ1012 Project (1993–96) are largely recognized. |
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Derechos:
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(c) American Institute of Physics, 1997
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Tipo de documento:
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article
publishedVersion |
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Editor:
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American Institute of Physics
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