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Author: Singh, D.J. × DDC: 620 ×

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    Discovery of TaFeSb-based half-Heuslers with high thermoelectric performance
    (London : Nature Publishing Group, 2019) Zhu, H.; Mao, J.; Li, Y.; Sun, J.; Wang, Y.; Zhu, Q.; Li, G.; Song, Q.; Zhou, J.; Fu, Y.; He, R.; Tong, T.; Liu, Z.; Ren, W.; You, L.; Wang, Z.; Luo, J.; Sotnikov, A.; Bao, J.; Nielsch, K.; Chen, G.; Singh, D.J.; Ren, Z.
    Discovery of thermoelectric materials has long been realized by the Edisonian trial and error approach. However, recent progress in theoretical calculations, including the ability to predict structures of unknown phases along with their thermodynamic stability and functional properties, has enabled the so-called inverse design approach. Compared to the traditional materials discovery, the inverse design approach has the potential to substantially reduce the experimental efforts needed to identify promising compounds with target functionalities. By adopting this approach, here we have discovered several unreported half-Heusler compounds. Among them, the p-type TaFeSb-based half-Heusler demonstrates a record high ZT of ~1.52 at 973 K. Additionally, an ultrahigh average ZT of ~0.93 between 300 and 973 K is achieved. Such an extraordinary thermoelectric performance is further verified by the heat-to-electricity conversion efficiency measurement and a high efficiency of ~11.4% is obtained. Our work demonstrates that the TaFeSb-based half-Heuslers are highly promising for thermoelectric power generation.
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    Spin-orbit coupling control of anisotropy, ground state and frustration in 5d2 Sr2MgOsO6
    (London : Nature Publishing Group, 2016) Morrow, Ryan; Taylor, Alice E.; Singh, D.J.; Xiong, Jie; Rodan, Steven; Wolter, A.U.B.; Wurmehl, Sabine; Büchner, Bernd; Stone, M.B.; Kolesnikov, A.I.; Aczel, Adam A.; Christianson, A.D.; Woodward, Patrick M.
    The influence of spin-orbit coupling (SOC) on the physical properties of the 5d2 system Sr2MgOsO6 is probed via a combination of magnetometry, specific heat measurements, elastic and inelastic neutron scattering, and density functional theory calculations. Although a significant degree of frustration is expected, we find that Sr2MgOsO6 orders in a type I antiferromagnetic structure at the remarkably high temperature of 108 K. The measurements presented allow for the first accurate quantification of the size of the magnetic moment in a 5d2 system of 0.60(2) μB –a significantly reduced moment from the expected value for such a system. Furthermore, significant anisotropy is identified via a spin excitation gap, and we confirm by first principles calculations that SOC not only provides the magnetocrystalline anisotropy, but also plays a crucial role in determining both the ground state magnetic order and the size of the local moment in this compound. Through comparison to Sr2ScOsO6, it is demonstrated that SOC-induced anisotropy has the ability to relieve frustration in 5d2 systems relative to their 5d3 counterparts, providing an explanation of the high TN found in Sr2MgOsO6.