Colossal anomalous Nernst effect in a correlated noncentrosymmetric kagome ferromagnet

Abstract

The transverse voltage generated by a temperature gradient in a perpendicularly applied magnetic field, termed the Nernst effect, has promise for thermoelectric applications and for probing electronic structure. In magnetic materials, an anomalous Nernst effect (ANE) is possible in a zero magnetic field. We report a colossal ANE in the ferromagnetic metal UCo0.8Ru0.2Al, reaching 23 microvolts per kelvin. Uranium’s 5f electrons provide strong electronic correlations that lead to narrow bands, a known route to producing a large thermoelectric response. In addition, uranium’s strong spin-orbit coupling produces an intrinsic transverse response in this material due to the Berry curvature associated with the relativistic electronic structure. Theoretical calculations show that in UCo0.8Ru0.2Al at least 148 Weyl nodes, and two nodal lines, exist within 60 millielectron volt of the Fermi level. This work demonstrates that magnetic actinide materials can host strong Nernst and Hall responses due to their combined correlated and topological nature.

Large magnon-induced anomalous Nernst conductivity in single-crystal MnBi

“…Such a large ANE thermopower is higher than most reported values 5 , 6 , 7 , 8 , 9 , 11 and is only second to a recently reported compound, UCo 0.8 Ru 0.2 Al. 28 The S zyx of B2 ⊥ reaches ∼7 μV/K at 110 K, comparable with that of B1 ⊥ in the same temperature range. For B1 ⊥ , the S zyx can reach saturation at 1 T from 80 to 140 K. When the SR process is completed, our crystals do not reach saturation magnetization at 1.4 T; thus no saturation in S zyx is observed on B1 ⊥ from 180 to 300 K. At room temperature, our measured ANE thermopower is 2.5 μV/K for B1 ⊥ and 1.5 μV/K for B2 ⊥ .…”

“…Lacking the detailed band parameters and scattering parameters, we are unable at this time to further quantify the value of C. Finally, in Figure 4D we compare our experimental ANE thermopower S ANE and transverse thermoelectric conductivity a ANE with other magnetic materials with large ANE responses. [5][6][7][8][9]28 MnBi's S ANE is about 25% higher than that of Fe 3 Ga and Co 2 MnGa, for both of which the intrinsic contributions are recognized as the origin of the large ANE signal. More importantly, the anomalous Nernst conductivity of MnBi is outstanding among all magnetic materials, reaching over 40 A/Km.…”

Giant anomalous Nernst signal in the antiferromagnet YbMnBi2

“… a , Comparison of the absolute values of | α ANE |/ M , | S ANE |/ M and M of YbMnBi 2 in the b c configuration (160 K) with those of other compounds with large ANE thermopowers—namely, the ferromagnets Fe 3 Ga (300 K) 2 , Co 2 MnGa (300 K) 3 , 9 , Co 3 Sn 2 S 2 (80 K) 7 , UCo 0.8 Ru 0.2 Al (40 K) 15 , MnBi (80 K) 37 , Ga 1− x Mn x As (10 K) 42 , and the chiral antiferromagnets Mn 3 Sn (300 K) 6 , 12 and Mn 3 Ge (300 K) 10 , 32 . Antiferromagnets are marked as AFM, and other materials are all ferromagnets.…”

“… 2 ) showed ANE thermopowers of 3–8 μV K −1 and ANE conductivities of 0.5–5 A m −1 K −1 , and recently UCo 0.8 Ru 0.2 Al (ref. 15 ) was reported to have a colossal ANE thermopower of 23 μV K −1 and a large ANE conductivity of 15 A m −1 K −1 . So far, large ANEs have been reported in only a few topological ferromagnets, and topological noncollinear antiferromagnets have rarely been studied, except for Mn 3 X ( X = Sn and Ge) 6 , 10 , 12 .…”

Giant anomalous Hall and anomalous Nernst Conductivities in Antiperovskites and their Tunability via Magnetic Fields

“…Furthermore, the kagome lattice is one of the determinants to induce enhanced ANC. 29,35 From this perspective, antiperovskites are fascinating, host a kagome lattice in the (111) plane, and also, the Weyl nodes can be tuned with applied biaxial strain as observed in noncollinear Mn 3 PdN. 13 In this work, we systematically evaluated the AHC and ANC of 35 cubic ferromagnetic APV compounds M 3 XZ (Table I and Figure 1).…”