Nanomagnetism Triggering Carriers Double-Resistance Conduction and Excellent Flexible Thermoelectrics

Nanomagnetism may enable electrical conductivity and Seebeck coefficient to be decoupled and can potentially lead to remarkable enhancements in thermoelectric (TE) performance, however, their physical mechanisms have not been explored. Herein, it is shown that the nanomagnetism from Fe and Fe₃O₄ nanoparticles embedded in Bi_0.5Sb_1.5Te₃/epoxy flexible films can lead to the carriers splitting into spin-up and spin-down conductive branches with different resistances and mobilities due to the exchange interaction between the spin of carriers and the nanomagnetism. The double-resistance conduction of carriers may well explain the decoupling of electrical conductivity and Seebeck coefficient and their simultaneous enhancements in the thermo-electro-magnetic flexible films. It is further shown that the maximum dimensionless figure of merit of the thermo-electro-magnetic flexible films reaches between 1.2 and 1.4 at room temperature, and their five-level cascaded device based on the films achieves a temperature drop of 3.1 K through in-plane heat dissipation, making a new record for printing flexible TE films and devices. The double-resistance conduction of carriers also reveals a deep physical mechanism for magneto-enhanced TE performance of bulk thermoelectrics.