Seminar by Prof. Dino Fiorani, honorary doctor 2020

  • Datum: –10.00
  • Plats: Ångströmlaboratoriet Å4001
  • Föreläsare: Dino Fiorani, Institute of Structure of Matter, National Research Council of Italy (CNR)
  • Kontaktperson: Roland Mathieu
  • Seminarium

EFFECTS OF MOLECULAR COATING ON THE MAGNETIC PROPERTIES OF NANOPARTICLES

Since the surface plays a key role on the magnetic properties of nanoparticles, in the last years a growing interest has been devoted to surface modifications produced by suitable coating in order to tune them for specific applications. The change in the magnetic properties is correlated with the specific coordinating functional group bound onto the nanoparticle surface. The effect of the interaction between organic coating and surface of two spinel ferrite nanoparticles will be described.
a) CoFe2O4 particles coated with two different organic ligands (diethylene glycol: DEG) and oleic acid (OA);
b) MnFe2O4 particles coated with Albumin.
The investigation was carried out combining magnetization and Mossbauer spectroscopy measurements with physical modeling by DFT and Monte Carlo simulations. The ensemble of results (1) on CoFe2O4 particles (average size: 5 nm) show a higher blocking temperature and saturation magnetization and a lower coercive field for the DEG coated particles with respect to the OA coated ones. This is due to the larger magnetic moment, resulting in the enhancement of dipolar interaction strength, and to the lower magnetocrystalline anisotropy of the DEG sample, as shown by DFT calculations.
The ensemble of results (2) on Albumin coated MnFe2O4 particles (average size: 2 nm) show that the coating produces a change in the structure, size and shape distribution of clusters of exchange coupled particles. Moreover, the coating produces the decrease of the saturation magnetization and surface anisotropy, resulting in a large decrease of the coercive field. Remarkably, the coating does not affect the strength of the dipolar interactions, as shown by the same Superspin Glass freezing temperature in the uncoated and coated particles.

1) M. Vasilakaki, N. Ntallis, N. Yaacoub, G. Muscas, D. Peddis and K.N. Trohidou, Nanoscale 10(45), 21244 (2018)
2) M. Vasilakaki, N. Ntallis, M. Bellusci, F. Varsano, R. Mathieu, D. Fiorani, D. Peddis and K.N. Trohidou, Nanotechnology 31, 025707 (2020)