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Magnetic properties of silica coated spindle-type hematite particles

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Publication date 2011
Author Reufer M, Dietsch H, Gasser U, Grobety B, Hirt AM, Malik VK, Schurtenberger P,
Project Phasenverhalten von Mischungen von Ferrofluiden und nicht- magnetischen Kolloiden
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Original article (peer-reviewed)

Journal JOURNAL OF PHYSICS-CONDENSED MATTER
Volume (Issue) 23(6)
Page(s) 065102-1 - 11
Title of proceedings JOURNAL OF PHYSICS-CONDENSED MATTER

Abstract

Magnetic properties of particles are generally determined from randomly oriented ensembles and the influence of the particle orientation on the magnetic response is neglected. Here, we report on the magnetic characterization of anisotropic spindle-type hematite particles. The easy axis of magnetization is within the basal plane of hematite, which is oriented perpendicular to the spindle axis. Two standard synthesis routes are compared and the effects of silica coating and particle orientation on the magnetic properties are investigated. Depending on the synthesis route we find fundamentally different magnetic behavior compatible with either single domain particles or superparamagnetic sub-units. Furthermore, we show that silica coating reduces the mean blocking temperature to nearly room temperature. The mechanical stress induced by the silica coating appears to reduce the magnetic coupling between the sub-units.
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