Thermoelectricity under magnetic control
Thermoelectric generators are devices that convert heat flow into usable electric power by harnessing the Seebeck effect. Unlike traditional heat engines, these devices possess attractive qualities such as compactness, low maintenance requirements, and the absence of moving components. However, the historical challenge associated with these devices has been their limited efficiency and versatility, which has hindered wide-spread adoption.
In recent years, significant progress has been made in improving the performance of thermoelectric generators. One notable advancement was the discovery of the “giant thermoelectric effect” in strongly polarized ferromagnet/superconductor junctions. In a recently accepted manuscript [https://doi.org/10.1103/PhysRevLett.130.237001], César González-Ruano and Diego Caso from the MAGNETRANS-UAM group led by Farkhad Aliev and their coauthors present compelling experimental evidence illustrating the controllability of thermopower in V/MgO/Fe/MgO/Fe/Co superconductor-spin valve hybrids, through the manipulation of the magnetic alignment of the ferromagnetic electrodes. Significantly, their findings validate the theoretical prediction [https://doi.org/10.1103/PhysRevB.106.094514], made in collaboration with the group of Jacob Linder from the Norwegian University of Science and Technology, that the rotation of a single magnetic layer not only profoundly influences the thermoelectric effect, but can even reverse its direction when the ferromagnetic electrodes are optimally arranged in an antiparallel configuration. This ability to control the thermopower's sign opens up possibilities for designing Peltier elements based on superconducting spin valves. The groundbreaking research conducted by Gonzalez-Ruano and colleagues offers exciting prospects for enhancing the efficiency and performance of thermoelectric devices.
