In-Depth Study of Magnetic and Thermoelectric Properties of Gadolinium Offers Insight Toward New Spin and Quantum Driven Thermoelectric Materials Design Strategies

Gadolinium, the element with the highest number of unpaired 4f electrons, provides an ideal system for exploring spin and quantum-mediated thermoelectric properties. Its thermopower shows three distinct regions at <100 K, 100-240 K, and >240 K, shaped by the phonon-drag, bipolar diffusion, magnon-drag, and quantum effects. We investigate the anomalous magneto-thermopower trends by probing the magnetic, electrical, and thermal properties versus magnetic field and temperature. Below 100K, the phonon-drag dominates thermopower, while the trend from 100K to 240K follows the diffusive multi-carrier transport properties. The Berry curvature-dominated anomalous Hall conductivity affects the carrier transport properties through modification of the group velocity. Magneto-thermopower measurements at higher temperatures reveal positive magnon-drag thermopower and a negative diffusion contribution. The multifold spin and quantum effects lead to ~50% thermopower and ~70% zT enhancement near the Curie temperature (T_C~290K) despite >70% suppression of the magnon contribution at 12T. The magnetic field-driven spin and quantum effects distilled from this system offer a fundamentally new viewpoint to extend thermoelectric research to magnetic and quantum materials.