Flexible, elastomeric, and superparamagnetic substrates were prepared by electrospirining a solution of elastomeric polyurethane containing ferrite nanoparticles (similar to 14 nm) of Mn-Zn-Ni. The flexible mats were characterized in terms of fiber morphology and magnetic properties. Field emission scanning electron microscopy (FESEM) indicated that the diameter of these composite fibers was similar to 300-500 nm. Furthermore, the back-scattered electron FESEM images indicated agglomeration of the nanoparticles at higher wt % (ca. 17-26 wt %) loading in the electrospun fibers. The induced specific magnetic saturation and the relative permeability were found to increase linearly with increasing wt %, loading of the ferrite nanoparticles on the submicron electrospun fibers. A specific magnetic saturation of 1.7-6.3 emu/g at ambient conditions indicated superparamagnetic behavior of these composite electrospun substrates. (c) 2006 Wiley Periodicals, Inc.