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Improvement of Thermoelectricity Through Magnetic Interactions in Layered Cr 2 Ge 2 Te 6
Author(s) -
Peng Chengxiao,
Zhang Guangbiao,
Wang Chao,
Yan Yuli,
Zheng Haiwu,
Wang Yuanxu,
Hu Ming
Publication year - 2018
Publication title -
physica status solidi (rrl) – rapid research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.786
H-Index - 68
eISSN - 1862-6270
pISSN - 1862-6254
DOI - 10.1002/pssr.201800172
Subject(s) - condensed matter physics , seebeck coefficient , paramagnetism , thermoelectric effect , magnetism , figure of merit , materials science , magnetic semiconductor , electrical resistivity and conductivity , fermi level , magnetic moment , thermoelectric materials , doping , physics , electron , thermodynamics , optoelectronics , quantum mechanics
The magnetism is proposed as a way to improve thermoelectricity, which may overcome the tradeoff between electrical conductivity and Seebeck coefficient. The correlation between magnetic configurations and thermoelectricity in layered magnetic semiconductor Cr 2 Ge 2 Te 6 has been investigated using first‐principles calculations, combined with semi‐classical Boltzmann theory. The electronic structures and relevant transport properties for paramagnetic phase have been stimulated. Special quasi‐random structure (SQS) is employed to simulate electronic properties of paramagnetic state corresponding to spin‐disordered configurations. The temperature dependence of calculated Seebeck coefficient, electrical conductivity, and the figure of merit ZT is in good agreement with experimental values for paramagnetic phase. For p‐type Cr 2 Ge 2 Te 6 , the maximum ZT can reach 0.54 at 830 K and the carrier concentration a value of 2.1 × 10 20 cm −3 . The calculated figure of merit can further increase by 42% compared to the maximum experimental result by optimized doping level. Cr 2 Ge 2 Te 6 without spin polarization shows a metal electric band structure, which deviates from the semiconductor of truth. This means that magnetic interactions play an important role in electronic structure and result in an excellent thermoelectricity of paramagnetic Cr 2 Ge 2 Te 6 . High band valley degeneracy, flat valence bands, and the localized partial density of states (PDOS) of magnetic atoms near Fermi surface induce a large Seebeck coefficient, meanwhile a good electrical conductivity is maintained in this magnetic semiconductor with high symmetry.