On the magnetic anisotropy and nuclear relaxivity effects of Co and Ni doping in iron oxide nanoparticles

We report a systematic experimental study of the evolution of the magnetic and relaxometric properties as a function of metal (Co, Ni) doping in iron oxide nanoparticles. A set of five samples, having the same size and ranging from stoichiometric cobalt ferrite (CoFe2O4) to stoichiometric nickel fer...

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Bibliographic Details
Published in:Journal of applied physics 2016-04, Vol.119 (13)
Main Authors: Orlando, T., Albino, M., Orsini, F., Innocenti, C., Basini, M., Arosio, P., Sangregorio, C., Corti, M., Lascialfari, A.
Format: Article
Language:English
Subjects:
ANISOTROPY
Applied physics
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
Cobalt ferrites
COBALT OXIDES
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
DISPERSIONS
DOPED MATERIALS
Doping
Evolution
FERRITE
FERRITES
IRON OXIDES
Magnetic anisotropy
Magnetic permeability
Magnetic properties
NANOPARTICLES
Nickel ferrites
NICKEL OXIDES
NMR
NUCLEAR MAGNETIC RESONANCE
STOICHIOMETRY
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Summary:We report a systematic experimental study of the evolution of the magnetic and relaxometric properties as a function of metal (Co, Ni) doping in iron oxide nanoparticles. A set of five samples, having the same size and ranging from stoichiometric cobalt ferrite (CoFe2O4) to stoichiometric nickel ferrite (NiFe2O4) with intermediate doping steps, was ad hoc synthesized. Using both DC and AC susceptibility measurements, the evolution of the magnetic anisotropy depending on the doping is qualitatively discussed. In particular, we observed that the height of the magnetic anisotropy barrier is directly proportional to the amount of Co, while the Ni has an opposite effect. By Nuclear Magnetic Resonance Dispersion (NMR-D) experiments, the experimental longitudinal r 1 and transverse r 2 relaxivity profiles were obtained, and the heuristic theory of Roch et al. was used to analyze the data of both r 1 and, for the first time, r 2. While the experimental and fitting results obtained from r 1 profiles were satisfying and confirmed the anisotropy trend, the model applied to r 2 hardly explains the experimental findings.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4945026