Magnetic measurements of suspended functionalised ferromagnetic beads under DC applied fields

Luis De Los Santos V., Justin Llandro, Dongwook Lee, Thanos Mitrelias, Justin J. Palfreyman, Thomas J. Hayward, Jos Cooper, J. A.C. Bland, Crispin H.W. Barnes, Juan L. Arroyo C., Martin Lees

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


In this work, a simple technique to obtain the hysteresis loops of magnetic beads (Spherotech Inc.) in liquid suspension is presented. The magnetic measurements were taken in a DC Magnetic Property Measurement System (MPMS-SQUID sensor). Samples were based on ferromagnetic beads (surface-functionalized NH2, mean diameter 4.32 μm) prepared in three conditions: dry, suspended in sucrose solution and in suspension after functionalization with fluorophore. Special small containers (1.3 cm long) made of non magnetic plastic were designed to hold the beads in liquid. The results indicate that the bead's remnant magnetization is half of the value at maximum applied field in all cases. However, due to the additional degrees of rotational freedom, beads suspended in a liquid do not present coercivity. The use of ferromagnetic beads and magnetic elements of different architectures for applications in bioassays is also discussed. Crown

Original languageEnglish
Pages (from-to)2129-2134
Number of pages6
JournalJournal of Magnetism and Magnetic Materials
Issue number14
Publication statusPublished - 2009 Jul 1
Externally publishedYes


  • Magnetic hysteresis
  • Magnetic material
  • Magnetoelectric effect
  • Magnetoelectronic

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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