This paper describes preparation and characterization of magnetic core-shell nanoparticles with modulated magnetic core diameter and various thickness of the non-magnetic shell. Ag, Au and Cu are used as spacing layer metals. Nanoparticles were fabricated by the synthetic method based on modified seeds. During the preparation, the thicknesses of the core and shell were changed to control the influence of nanoparticles' magnetic properties in respect to the composition and thickness of the spacer material. Obtained nanoparticles were examined by X-ray diffraction, transmission electron microscopy, infrared spectroscopy and differential scanning calorimetry. Magnetic properties of the nanoparticles were tested by Mossbauer spectroscopy. (C) 2015 Elsevier B.V. All rights reserved.