Paramagnon drag in high thermoelectric figure of merit Li-doped MnTe.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31548980.
- Also identified by DOI 10.1126/sciadv.aat9461 and PMC identifier 6744264.
- Licence recorded as CC BY-NC.
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Abstract
Local thermal magnetization fluctuations in Li-doped MnTe are found to increase its thermopower α strongly at temperatures up to 900 K. Below the Néel temperature (<i>T</i> <sub>N</sub> ~ 307 K), MnTe is antiferromagnetic, and magnon drag contributes α<sub>md</sub> to the thermopower, which scales as ~<i>T</i> <sup>3</sup>. Magnon drag persists into the paramagnetic state up to >3 × <i>T</i> <sub>N</sub> because of long-lived, short-range antiferromagnet-like fluctuations (paramagnons) shown by neutron spectroscopy to exist in the paramagnetic state. The paramagnon lifetime is longer than the charge carrier-magnon interaction time; its spin-spin spatial correlation length is larger than the free-carrier effective Bohr radius and de Broglie wavelength. Thus, to itinerant carriers, paramagnons look like magnons and give a paramagnon-drag thermopower. This contribution results in an optimally doped material having a thermoelectric figure of merit <i>ZT</i> > 1 at <i>T</i> > ~900 K, the first material with a technologically meaningful thermoelectric energy conversion efficiency from a spin-caloritronic effect.