Skip to main content
Log in

Thermal treatment to enhance saturation magnetization of superparamagnetic Ni nanoparticles while maintaining low coercive force

  • Research Paper
  • Published:
Journal of Nanoparticle Research Aims and scope Submit manuscript

Abstract

Superparamagnetic nanoparticles capped by insulators have the potential to decrease eddy current and hysteresis losses. However, the saturation magnetization (Ms) decreases significantly with decreasing the particle size. In this study, superparamagnetic Ni nanoparticles having the mean size of 11.6 ± 1.8 nm were synthesized from the reduction of Ni(II) acetylacetonate in oleylamine with the addition of trioctylphosphine, indicating the coercive force (Hc) less than 1 Oe. Thermal treatments of the Ni nanoparticles were investigated as a method to enhance the Ms. The results indicated that the M s was enhanced by an increase of the Ni mass ratio with increasing thermal treatment temperature. However, the decomposition behavior of the capping layers indicated that their alkyl chains actively decomposed at temperatures above 523 K to form Ni3P via reaction between Ni and P, resulting in particle growth with a significant increase in the Hc. Therefore, the optimal temperature was determined to be 473 K, which increased the Ni ratio without formation of Ni3P while maintaining particle sizes with superparamagnetic properties. Further, the Ms could be improved by 22% (relative to the as-synthesized Ni nanoparticles) after thermal treatment at 473 K while maintaining the Hc to be less than 1 Oe.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10
Fig. 11
Fig. 12

Similar content being viewed by others

References

Download references

Acknowledgments

The authors would like to thank Mr. Satoru Kosaka and Mr. Daisuke Fujimaki for undertaking the elemental ratio analyses, and Mr. Masami Yamamoto for undertaking the TD-MS analyses, and Materials Science and Technology of Japan (MST) for undertaking the STEM-EDS observations, and Quantum Design Japan for undertaking the ZFC-FC measurements.

Author information

Authors and Affiliations

Authors

Contributions

The three authors equally contributed to this research. Dr. Ishizaki compiled the data and wrote the manuscript.

Corresponding author

Correspondence to Toshitaka Ishizaki.

Ethics declarations

Conflict of interest

The authors declare that they have no conflicts of interest.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Ishizaki, T., Yatsugi, K. & Akedo, K. Thermal treatment to enhance saturation magnetization of superparamagnetic Ni nanoparticles while maintaining low coercive force. J Nanopart Res 20, 116 (2018). https://doi.org/10.1007/s11051-018-4206-6

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doi.org/10.1007/s11051-018-4206-6

Keywords

Navigation