Functional materials, specifically those which respond to external stimuli, such as magnetic and electrical fields, are increasingly important for many green energy technologies. They are being investigated from basic and applied sciences perspectives. Probably the best known of these materials are permanent magnets, which are used to supply a magnetic field and are widely applied in motors, generators, data storage, sensors, and actuators. Other examples of functional materials include soft magnets, magnetocalorics, and thermoelectrics.