Colorize magnetic nanoparticles using a search coil based testing method

Kai Wu, Yi Wang, Yinglong Feng, Lina Yu, Jian Ping Wang

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Different magnetic nanoparticles (MNPs) possess unique spectral responses to AC magnetic field and we can use this specific magnetic property of MNPs as "colors" in the detection. In this paper, a detection scheme for magnetic nanoparticle size distribution is demonstrated by using an MNPs and search-coils integrated detection system. A low frequency (50 Hz) sinusoidal magnetic field is applied to drive MNPs into saturated region. Then a high frequency sinusoidal field sweeping from 5 kHz to 35 kHz is applied in order to generate mixing frequency signals, which are collected by a pair of balanced search coils. These harmonics are highly specific to the nonlinearity of magnetization curve of the MNPs. Previous work focused on using the amplitude and phase of the 3rd harmonic or the amplitude ratio of the 5th harmonic over 3rd harmonic. Here we demonstrate to use the amplitude and phase information of both 3rd and 5th harmonics as magnetic "colors" of MNPs. It is found that this method effectively reduces the magnetic colorization error.

Original languageEnglish (US)
Pages (from-to)251-254
Number of pages4
JournalJournal of Magnetism and Magnetic Materials
StatePublished - Apr 15 2015

Bibliographical note

Funding Information:
Authors thank the partial support from the Institute of Engineering in Medicine at University of Minnesota . Parts of this work were carried out using the Characterization Facility which receives partial support from NSF through the NSF Minnesota MRSEC Program under Award Number DMR-0819885 and NNIN program.


  • Biomarker detection
  • Diagnostics
  • Magnetic coloring
  • Magnetic colorization
  • Magnetic nanoparticles
  • Mixing frequency signal

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