Giant Hall effect in superparamagnetic granular films

J. C. Denardin, M. Knobel*, Xixiang Zhang, A. B. Pakhomov

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review

34 Scopus citations

Abstract

A comprehensive review of the giant Hall effect (GHE) is presented, with emphasis on novel experimental data obtained in Ni-SiO2 and Co-SiO2 films prepared by co-sputtering. GHE is observed close to and on both sides of the metal-insulator transition. From the point of view of microscopic conduction mechanisms, this means a crossover from metallic conductivity with weak localization to tunneling, or hopping, between separate granules across insulating barriers. Magnetic percolation is also interrupted at this concentration of metal, leading to superparamagnetic behavior of the composite and blocking phenomena. Temperature dependencies of magnetization and extraordinary Hall coefficient in the composites near the critical concentration are compared. In single phase magnetic metals and alloys, the extraordinary Hall is believed to be directly proportional to the total magnetization, due to side jumps or skew scattering. In a metal-insulator composite, only those electrons traveling in conduction critical paths can contribute to the Hall signal, thus only magnetization of the material belonging to these paths is important in the Hall measurements. Comparison with the magnetic results leads to new possibilities in understanding both the electronic and magnetic properties of granular nanocomposites.

Original languageEnglish (US)
Pages (from-to)15-22
Number of pages8
JournalJournal of Magnetism and Magnetic Materials
Volume262
Issue number1
DOIs
StatePublished - May 1 2003
EventVision Geometry VII - San Diego, CA, United States
Duration: Jul 20 1998Jul 22 1998

Keywords

  • Giant Hall effect
  • Granular systems
  • Magnetic nanoparticles
  • Spin-dependent electronic transport

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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