Electron localization in Co/Ni superlattices
| Autor: | Sihong Kim, Ivan K. Schuller, J. M. Gallego, David Lederman |
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| Rok vydání: | 1996 |
| Předmět: | |
| Zdroj: | Physical Review B. 54:R5291-R5294 |
| ISSN: | 1095-3795 0163-1829 |
| DOI: | 10.1103/physrevb.54.r5291 |
| Popis: | The residual resistivity in Co/Ni superlattices is shown to oscillate as a function of superlattice period for fixed Co to Ni thickness ratio. Additional experimental evidence shows that this behavior is enhanced when randomness is artificially introduced in the individual layer thickness. We analyze this in terms of a scattering mechanism associated with the presence of localized electron eigenstates near the Fermi level in the metallic superlattices. A one-dimensional tight-binding calculation shows that localized states appear close to superlattice periods for which the resistivity exhibits maxima. @S0163-1829~96!50632-6# Since the introduction of the superlattice concept, 1 much progress has been made in engineering new types of materials with interesting physical properties. Recent improvements in the quantitative structural analysis of thin films make the identification of intrinsic properties unrelated to structural disorder possible. 2 The successful growth and thorough structural characterization of ferromagnetic/ ferromagnetic Co/Ni was recently reported. 3 Subsequently, an oscillatory dependence of the resistivity ( r) and anisotropic magnetoresistance ~AMR! on the Co or Ni thickness in Co/Ni superlattices was discovered. 4 Possible explanations of these oscillations are zone folding of the superlattice energy band and electron localization. In this paper, we report on further experiments which indicate that electron localization may be responsible for the oscillations. A model calculation of the energy eigenvalues of the localized states, based on a one-dimensional tight-binding model, is consistent with the observed resistivity oscillations. Epitaxial Co/Ni ~fcc/fcc! superlattices were grown by molecular-beam epitaxy ~MBE! along the @111# direction on single crystal @11.0# sapphire substrates. Sample growth, structural characterization, and resistivity measurements were similar to those presented previously. 3,4 |
| Databáze: | OpenAIRE |
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