Synthesis and magnetic properties of core-shell structured (NiCo)O(AFM)-NiCo(FM) magnetic nanoparticles

B. Jeyadevan, C. N. Chinnasamy, O. Perales-Perez, Y. Iwasaki, A. Hobo, K. Shinoda, K. Tohji, A. Kasuya

Research output: Contribution to journalConference articlepeer-review

12 Citations (Scopus)


We have succeeded in the synthesis of nanometer size monodispersed Ni-Co metal particles through the modified-polyol process. Ni-Co metal particles of about 40 and 100 nm with Co-rich core and Ni-rich shell were produced by the manipulation of the reaction kinetics through a suitable selection of hydroxyl ion concentration in the ethylene glycol-Ni-Co system. Furthermore, core-shell structured (NiCo)O(AFM)-NiCo(FM) was produced by oxidizing particles at 533 K in air for different times. The magnetic properties, especially the exchange-bias (HE) fields of 40 and 100-nm core-shell structured particles synthesized under similar conditions behaved differently. However, their behavior was explained considering exchange biased interactions at (NiCo)O(AFM)-NiCo(FM), and (Co)O(AFM)-Co(FM) interfaces with two different exchange coupling constants. The 40 nm particles oxidized for 4h and composed of (NiCo)O(AFM)-NiCo(FM), exhibited a maximum HE field of 36 and 201 Oe at 298 and 77 K, respectively.

Original languageEnglish
Pages (from-to)2595-2597
Number of pages3
JournalIEEE Transactions on Magnetics
Issue number5 I
Publication statusPublished - 2002 Sept
Event2002 International Magnetics Conference (Intermag 2002) - Amsterdam, Netherlands
Duration: 2002 Apr 282002 May 2


  • Core-shell structured nanoparticles
  • Exchange-bias
  • Nanocrystalline Ni-Co particles
  • Polyol process


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