A composite material can include a grain component and a nanostructured grain boundary component. The nanostructured grain boundary component can be insulating and magnetic, so as to provide greater continuity of magnetization of the composite material. The grain component can have an average grain size of about 0.5-50 micrometers. The grain boundary component can have an average grain size of about 1-100 nanometers. The nanostructured magnetic grain boundary material has a magnetic flux density of at least about 250 mT. The grain component can comprise MnZn ferrite particles. The nanostructured grain boundary component can comprise NiZn ferrite nanoparticles. Core components and systems thereof can be manufactured from the composite material.