Magnetic properties of Ni and Ni-Cu nanoparticles

Nanoparticles of pure Ni and NiCu solid solution were synthesized by the solgel method at 400600 degrees C. The particle sizes and values of specific surface of powders were dependent on the synthesis temperature. The magnetization of the obtained powders was studied using a high-temperature magnetic balance. The Curie temperature for particles of pure nickel did not depend on their size but the specific magnetization at 300?K decreased linearly with increasing specific surface area of particles. For particles of the NiCu binary solid solutions, the Curie temperature and values of magnetization increased with decreasing particle size for particles with diameters up to values less than 100?nm. The amount of adsorbed copper on the particles surface, the change of nickel concentration in the volume of the particles and the Curie temperatures, depending on the Cu (Ni) concentration in a volume of particles, were calculated using the Gibbs equation. The calculations made in the framework of a perfect solution showed qualitative agreement between experimental and calculated values of the Curie temperature for the system NiCu.