Detection of iron-oxide magnetic nanoparticles using magnetic tunnel junction sensors with conetic alloy

Z. Q. Lei, Chi Wah Leung, L. Li, G. J. Li, G. Feng, A. Castillo, P. J. Chen, P. T. Lai, P. W.T. Pong

Research output: Journal article publicationJournal articleAcademic researchpeer-review

5 Citations (Scopus)


We demonstrated the detection of 20-nm iron-oxide magnetic nanoparticles (MNPs) using Al2O3magnetic tunnel junction sensors (MTJs) with Conetic alloy. Conetic alloy Ni77Fe14Cu5Mo4was deposited as the MTJ free layer and pinned layer due to its magnetically soft properties. The magnetoresistance (MR) curves of MTJs with Conetic alloy showed tunneling magnetoresistance of 8.0% with small hysteresis and high linearity in the sensing region, after applying an external magnetic field of 14 Oe along the hard axis. The sensitivity of the MTJ sensors with Conetic alloy was determined to be 0.3%/Oe within a linear region at room temperature. The MNPs of three different concentrations were successfully detected by the shifts of the MR loops of the MTJs, and it was observed that the resistance deviations of the MTJ sensors increased with the logarithm of MNP concentrations. The maximum resistance deviation was 0.16 Ω for an MNP concentration of 20.0 mg/mL. MTJ sensors, together with MNPs, are a promising platform for future biosensor applications, and this paper shows that Conetic alloy is feasible for improving the performance of this platform.
Original languageEnglish
Article number6027820
Pages (from-to)2577-2580
Number of pages4
JournalIEEE Transactions on Magnetics
Issue number10
Publication statusPublished - 1 Oct 2011


  • Iron-oxide magnetic nanoparticles
  • magnetic sensors
  • magnetic tunnel junction (MTJ)

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering


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