Magnetic properties of annealed core-shell CoPt nanoparticles

Nano Letters
Jean-Yves BigotJinwoo Cheon

Abstract

A precise control and understanding of the magnetization dynamics of nanostructures is an important topic in applied nanosciences. Herein, we perform such control by annealing crystalline (Co/core)-(Pt/shell) nanoparticles. Using electron tomography, temperature dependent electron microscopy and time-resolved magneto-optics, we establish a clear correlation between the magnetization dynamics and the crystalline structure of the nanoparticles. For a mild laser annealing (370 K) the Co-Pt nanoparticles keep their core-shell structure and remain superparamagnetic with a blocking temperature T(B) = 66 K. Their time-resolved reflectivity shows that they are locally organized into a supra-crystalline ordered layer in the region of the laser spot. In contrast, a thermal annealing at higher temperatures (up to 700 K) modifies the structure of the individual nanoparticles into a CoPt crystalline ferromagnetic phase, with T(B,anneal) = 347 K. Correspondingly, the magneto-crystalline anisotropy of the annealed CoPt nanoparticles increases and their magnetization dynamics displays a motion of precession, characteristic of ferromagnetic nanostructures and which is absent in the superparamagnetic Co-Pt core-shells.

References

Sep 25, 1998·Science·M BruchezA P Alivisatos
Dec 1, 1993·Physical Review. B, Condensed Matter·S A MajetichS W Staley
Sep 6, 2000·Physical Review Letters·C VoisinM Broyer
Jun 13, 2002·Physical Review Letters·M Van KampenB Koopmans
Feb 7, 2004·Science·Frédéric DumestrePeter Fejes
Apr 14, 2005·Nano Letters·Christopher LooRebekah Drezek
May 16, 2009·ACS Nano·Carly S LevinNaomi J Halas
Oct 16, 2009·Nature·Dmitri V TalapinChristopher B Murray
Dec 5, 2009·Chemical Reviews·Dmitri V TalapinElena V Shevchenko
Apr 7, 2010·Physical Review Letters·O KasyutichJ van Lierop

❮ Previous
Next ❯

Citations

Feb 12, 2015·The Journal of Chemical Physics·Shuaidi ZhangBaiyun Huang
May 9, 2015·Physical Chemistry Chemical Physics : PCCP·Gábor KovácsKonstantin M Neyman
Mar 14, 2013·Journal of Materials Chemistry. B, Materials for Biology and Medicine·Boi Hoa SanKyeong Kyu Kim
Nov 2, 2014·Physical Chemistry Chemical Physics : PCCP·Dharmesh Varade, Kazutoshi Haraguchi

❮ Previous
Next ❯

Related Concepts