Magnetic study of Fe3O4/Ag nanoparticles

Nanocomposites of Fe3O4 nanoparticles (NPs) impregnated with silver NPs display antibacterial properties and may be used in water treatment as disinfection agent. Three samples were synthesized: Fe3O4 NPs obtained by the precipitation method and additionally two samples with added silver NPs with mass ratio of Ag: Fe3O4 equal to 1: 100 and 2: 100. Magnetic properties of these samples were studied by SQUID magnetometry (in temperature range 2-300K and magnetic fields up to 70 kG) and magnetic resonance technique at RT. Temperature dependence of dc susceptibility revealed the blocking temperature close to RT in all three samples and allowed to determine the presence of single or multi-mode distribution of NP sizes in a particular sample. Isothermal magnetisation measurements showed that the presence of silver NPs, especially those with smaller sizes, decreases the saturation magnetisation. The shape of ferromagnetic loop registered at T - 2K was used to discuss the sizes of NP magnetic clusters in our samples. Conclusions obtained from analysis of the ferromagnetic resonance spectra were consistent with the propositions based on the magnetometric studies.