Spin Dynamics in Hybrid Iron Oxide-Gold Nanostructures

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Orlando T., Capozzi A., Umut E., Bordonali L., Mariani M., Galinetto P., ...More

JOURNAL OF PHYSICAL CHEMISTRY C, vol.119, no.2, pp.1224-1233, 2015 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 119 Issue: 2
  • Publication Date: 2015
  • Doi Number: 10.1021/jp509411v
  • Journal Name: JOURNAL OF PHYSICAL CHEMISTRY C
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.1224-1233
  • Dokuz Eylül University Affiliated: Yes

Abstract

We report a broadband H-1 NMR study of the spin dynamics of coated maghemite and goldmaghemite hybrid nanostructures with two different geometries, namely dimers and coreshells. All the samples have a superparamagnetic behavior, displaying a blocking temperature (T-B similar to 80 K (maghemite), similar to 105 K (dimer), similar to 150 K (coreshell)), and the magnetization reversal time follows the VogelFulcher law. We observed three different anomalies in H-1 NMR T(1)1 versus T that decrease in amplitude when increasing the applied magnetic field. We suggest that the anomalies are related to three distinct system dynamics: molecular rotations of the organic groups (240 < T < 270 K), superparamagnetic spin blockage (100 < T < 150 K), and surfacecore spin dynamics (T < 25 K). By fitting the T(1)1 data with a heuristic model, we achieved a good agreement with magnetic relaxation data and literature values for methyl group rotation frequencies.