Magnetoelectric interaction and transport behaviours in magnetic nanocomposite thermoelectric materials.

How to suppress the performance deterioration of thermoelectric materials in the intrinsic excitation region remains a key challenge. The magnetic transition of permanent magnet nanoparticles from ferromagnetism to paramagnetism provides an effective approach to finding the solution to this challenge. Here, we have designed and prepared magnetic nanocomposite thermoelectric materials consisting of BaFeO nanoparticles and BaInCoSb matrix. It was found that the electrical transport behaviours of the nanocomposites are controlled by the magnetic transition of BaFeO nanoparticles from ferromagnetism to paramagnetism. BaFeO nanoparticles trap electrons below the Curie temperature (T) and release the trapped electrons above the T, playing an 'electron repository' role in maintaining high figure of merit ZT. BaFeO nanoparticles produce two types of magnetoelectric effect-electron spiral motion and magnon-drag thermopower-as well as enhancing phonon scattering. Our work demonstrates that the performance deterioration of thermoelectric materials in the intrinsic excitation region can be suppressed through the magnetic transition of permanent magnet nanoparticles.