Magnon-bipolar carrier drag thermopower in antiferromagnetic/ferromagnetic semiconductors: Theoretical formulation and experimental evidence

Antiferromagnetic α-MnTe: Molten-Salt-Assisted Chemical Vapor Deposition Growth and Magneto-Transport Properties

“…Manganese telluride (MnTe) is a typical AF semiconductor with a moderate band gap of 1.25–1.46 eV. , Hexagonal NiAs-type α-MnTe is reported to be a stable phase under ambient conditions with a room-temperature Néel temperature ( T N ) of about 307 K . Magnetic anisotropy, susceptibility, planar Hall effect, thermal transport, and optical properties of α-MnTe have been predicted or confirmed in experiments.…”

Spin fluctuations yield zT enhancement in ferromagnets

“…Among these sources, magnetic heat capacity components can show strong magnetic field dependency based on the magnetic nature, provided that they can be quenched or modified with the external magnetic fields ( Polash et al., 2020b ; Ikeda and Gschneidner, 1982 ). Quenching of magnonic heat capacity depends on the spin-wave stiffness, exchange energy, spin number, and magnetization ( Polash and Vashaee, 2020 ). On the other hand, spin fluctuation contribution can be quenched by suppressing the inelastic spin-flip scattering ( Ikeda and Gschneidner, 1982 ).…”

“…Enhancing the entropy flow via electron gas by exploiting the intercoupled transport of electron, phonon, and spin has motivated a considerable amount of research recently in the thermoelectric society, which opened up a new direction in waste energy harvesting known as spin caloritronics ( Uchida et al., 2008 ; Liebing et al., 2011 ; Polash et al., 2021a ). Spins, the fundamental entropy carriers on electronic orbitals as a quantum nature of electrons and lattice ions as collective spin excitations, also known as magnons, offer a degree of freedom to engineer the counter-indicative thermoelectric material properties, namely, electrical conductivity (σ), thermal conductivity (κ), and thermopower (α), to design high-performance spin-driven thermoelectric materials ( Zheng et al., 2019 ; Polash et al., 2020a ; Polash and Vashaee, 2020 ). The ever-growing research interests in thermoelectric-based green energy harvesting have forcefully led to emergence of numerous pathways for designing materials for carbon-free energy harvesting applications with the broad societal needs of mitigating greenhouse and ozone-depletion potentials.…”

Thermal Management Systems and Waste Heat Recycling by Thermoelectric Generators—An Overview

“…Many more strategies have been studied to enhance the performance of thermoelectric compounds. The examples would be materials selection (as described in Figure 7) [64][65][66], sintering method (e.g., pondermotive force in microwave sintering enhances the diffusion of mobile ionic species and results in accelerating the solid-state reaction by increasing the collision probability) [67], band engineering (e.g., modulation doping, resonance level, and band convergence) [68][69][70][71][72][73][74], carrier pocket engineering [75][76][77], complex structures [78,79], carrier energy filtering [80,81], creation of resonant energy levels close to the band edges [70], low dimensional structures [82,83], magnetic interaction (e.g., carrier trap-ping and magnon (spin wave) excitations) [84,85], and lowering the thermal conductivity (e.g., phonon scattering) [58,[86][87][88][89][90].…”

“…to the band edges [70], low dimensional structures [82,83], magnetic interaction (e.g., carrier trapping and magnon (spin wave) excitations) [84,85], and lowering the thermal conductivity (e.g., phonon scattering) [58,[86][87][88][89][90].…”