Ferrofluids to improve field homogeneity in permanent magnet assemblies

Yannick P. Klein, Leon Abelmann, Han Gardeniers*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

2 Citations (Scopus)
23 Downloads (Pure)


A novel principle of passive magnetic field shimming for permanent magnet assemblies is introduced, based on defined amounts of a ferrofluid suspension contained in a microliter volume plastic container that is accurately positioned within the magnet bore. The ferrofluid volume acts as a micromagnet that compensates inhomogeneities in the magnetic field profile. A proof of principle is shown for a permanent magnet assembly, derived from a Halbach design, with two additional movable rings of magnets. These rings result in an average magnetic field strength of 1.06 T inside the bore, 19 % higher than the Halbach alone. Two options for field shimming with ferrofluids are shown: changing the material volume or choosing a ferrofluid with different saturation magnetization value. With the tested simple single-cube ferrofluid implementation the field homogeneity is improved from 86 ppm to 8 ppm over a sampling length of 5.5 mm. Better homogeneity is expected with more sophisticated ferrofluid arrangements. The complete assembly has a size of 5 × 5 × 4.2 cm3 and a weight of 332 g. The demonstrated concept is particularly attractive for mobile magnetic resonance systems, as it does not require electrical power during operation.

Original languageEnglish
Article number169371
JournalJournal of magnetism and magnetic materials
Early online date18 Apr 2022
Publication statusPublished - 1 Aug 2022


  • Ferrofluids
  • Halbach magnet
  • Homogeneous magnetic field
  • Permanent magnet
  • UT-Hybrid-D


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