Magnetic short time relaxation behavior of real ferrofluids

D. Eberbeck¹ - S. Hartwig¹ - U. Steinhoff¹ - L. Trahms¹ - Th. Götze² - K. Landfester³

¹ Physikalisch Technische Bundesanstalt Berlin, Fachlabor für Bioelektrizität und Biomagnetismus, Berlin, Germany
² Berlin Heart AG, Berlin, Germany
³ Max-Planck-Institut für Kolloid und Grenzflächenforschung, Golm/Potsdam, Germany

Abstract
The relaxation of the magnetic moment was measured with a high sensitive SQUID on three ferrofluids (G248, LF4, P6) with different structures of the magnetic composite particles. The ferrofluid G248 shows a relaxation signal, which scales linear with the concentration over three decades. The relaxation amplitude of G248 was higher than that of the sample LF4 with particles encapsulated in beads. As expected, the relaxation of magnetic moment of the samples with immobilized particles is much higher than that of fluid ones. In contrast the relaxation of MNP in the ferrofluid P6 is longer in fluid than in solid samples. This is discussed in the light of aggregation effects. Tables 1, Figs 4, Refs 10.