Effects of the silica content and temperature on the magnetic properties of Ni0.5Zn0.5Fe2O4/SiO2 nanocomposites have been studied by electron paramagnetic resonance (EPR) and superconducting quantum interference device (SQUID) technique. The content of TEOS in the starting solution affects the interaction between NiZn ferrite and silica, and then determines the particle size and the EPR properties. In addition, the SQUID properties of the composites were sensitive to particle size. It was observed that the saturation magnetization (M-s), remnant magnetization (M-r) and initial susceptibility (chi(i)) decreased with increasing SiO2 content. (C) 2005 Elsevier Ltd. All rights reserved.