Influence of NicoreAushell Nanoparticles' Morphology on Their Magnetic Properties

This paper reveals and describes the features of NicoreAushell nanoparticles' magnetic properties. Their activation energy of monodomain thermal relaxation (5.1 X 10(-20) J) and constant of magnetic crystalline anisotropy ((2.0-2.1) x 10(4) J/m(3)) are higher than bulk nickel has. Compared with nanostructured fcc-Ni powders, there is a decrease in the coercive force, the presence of "hard" magnetization, rising magnetization along with increasing degree of the nanoparticles' oxidation, and a decrease in magnetic characteristics to very low values at 300 K. These features are related to the structure of Ni cores (size and ico-structure of their units), shielding by Au shells, Au-Ni solid solution, and Ni(OH)(2), and their near-surface "frozen" spin subsystem. The latter depends on the sizes of nanocores and the Au-Ni interface. All of these features were discussed on the basis of material science research the authors provided for the NicoreAushell nanoparticles. This long-term study was completed by the present investigation as the most detailed for magnetic diamagnetic core-shell systems nanosized nowadays.