Magnetic composites exhibit distinct flux properties due to gradient interfaces. The composites can be used to improve fuel cells and batteries and effect transport and separation of different species of materials, for example, transition metal species such as lanthanides and actinides. A variety of devices can be made utilizing the composites including a separator, an electrode for channeling flux of magnetic species, an electrode for effecting electrolysis of magnetic species, a system for channeling electrolyte species, a system for separating particles with different magnetic susceptibilities, improved fuel cells, batteries, and oxygen concentrators. Some composites can be used to make a separator for distinguishing between two species of materials and a flux switch to regulate the flow of a chemical species. Some composites can control chemical species transport and distribution. Other composites enable ambient pressure fuel cells having enhanced performance and reduced weight to be produced. Still other composites enable rechargeable batteries to be made that have longer secondary cycle life and improved output power. Methods involving these composites provide distinct ways for these composites to be utilized.