Iron oxide nanoparticles (NPs) of 8 nm have been infiltrated into the pores of porous silicon. The aim is to create a superparamagnetic (SPM) nanocomposite system with maximized magnetic moment. Therefore the particle-particle distance versus the superparamagnetic behavior has been figured out. The blocking temperature T-B which indicates the transition between SPM behavior and blocked state is not only dependent on the particle size but also on the magnetic interactions between them which can be varied by the distance between the particles. Thus a modification, on the one hand of the pore-loading and on the other hand of the porous silicon morphology results in a composite material with a desired TB. Because both materials, the mesoporous silicon matrices as well as the Fe3O4-NPs offer low toxicity the system is a promising candidate for biomedical applications as e.g. magnetic field guided drug delivery. (C) 2013 Elsevier B.V. All rights reserved.