Abstract
We present a combined experimental and theoretical study of the longitudinal and transverse thermoelectric properties of ferrimagnetic spinels (, Se, Te). The thermoelectric power of all studied phases is positive and consists of two contributions; an almost linear diffusive thermopower observed at high temperature, and a strong enhancement below attributed to magnon drag. The diffusive part of thermopower and resistivity decreases from to Te, whereas the magnon drag enhancement is the biggest for , which has also the highest . The thermopower was calculated by DFT method using GGA, , and mBJ potentials. A good agreement with the experimental thermopower was achieved using GGA potential for and with mBJ potential for . The mBJ potential, which was designed for -type semiconductors, better describes the valence bands of that exhibit stronger -orbitals character than sulfide and selenide. The anomalous Nernst effect (ANE) is negative at room temperature for all phases, the highest absolute value /K is observed for and Se around room temperature, whereas ANE for is much smaller. A sign change of ANE to positive is observed at 285 K for and at 65 K for . The trend of anomalous Nernst conductivity is reproduced by Berry phase calculations if the renormalization of the bands due to the strong correlation effects is taken into account.
8 More- Received 27 January 2021
- Revised 13 June 2021
- Accepted 6 August 2021
DOI:https://doi.org/10.1103/PhysRevB.104.085146
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