Giant anomalous Nernst signal in the antiferromagnet YbMnBi2

Abstract

A large anomalous Nernst effect (ANE) is crucial for thermoelectric energy conversion applications because the associated unique transverse geometry facilitates module fabrication. Topological ferromagnets with large Berry curvatures show large ANEs; however, they face drawbacks such as strong magnetic disturbances and low mobility due to high magnetization. Herein, we demonstrate that YbMnBi2, a canted antiferromagnet, has a large ANE conductivity of ~10 A m−1 K−1 that surpasses large values observed in other ferromagnets (3–5 A m−1 K−1). The canted spin structure of Mn guarantees a non-zero Berry curvature, but generates only a weak magnetization three orders of magnitude lower than that of general ferromagnets. The heavy Bi with a large spin–orbit coupling enables a large ANE and low thermal conductivity, whereas its highly dispersive px/y orbitals ensure low resistivity. The high anomalous transverse thermoelectric performance and extremely small magnetization make YbMnBi2 an excellent candidate for transverse thermoelectrics.

Seebeck-driven transverse thermoelectric generation

“…Indeed, record-high SANE values of 23 μV K −1 in UCo0.8Ru0.2Al at low temperature [36], or 5-8 μV K −1 in L21-Co2MnGa and Co2Mn(Al,Si) at room temperature have been reported in such topological materials [14,16,23,25,27]. In additional, magnetic materials with other properties that are favored in applications, e.g., small magnetization [11,13,18,29,34,38], negative value of SANE [7,30], or large magnetic anisotropy [30,34,39] have also received attention to their transverse thermoelectric phenomena. Although orders of magnitude enhancement of SANE has been made in recent year from that of the traditional magnetic materials like Fe, Co, and Ni, the thermopower is still small compared to that of the SE and further enhancement is strongly required for practical applications.…”

High-Power-Density Energy-Harvesting Devices Based on the Anomalous Nernst Effect of Co/Pt Magnetic Multilayers

“…Since the measured ANE thermopowers vary only mildly with Pt thickness, we anticipate that the experimental thermoelectric conductivities will also vary only slightly with Pt thicknesses. This is at odds with the computed (intrinsic) thermoelectric conductivities, which depend very strongly on the thickness (note that in other systems, the first-principles-based calculations of the intrinsic ANE also fail to fully explain the origin of large Nernst thermopower 24 ). Hence, this indicates again that the origin of the main contribution to the ANE of Co/Pt multilayers is not intrinsic.…”

“…Scattering (unavoidable in real samples, particularly in those with large SOC) induces skew forces and side jump on the spin-polarized charge carriers. 24 Moreover, the net ANE can have contributions of all of the mentioned origins (including the Berry curvature). It is even possible that none of them is predominant.…”

Intercorrelated anomalous Hall and spin Hall effect in kagome-lattice Co$_3$Sn$_2$S$_2$-based shandite films

“…One should however be cautious in view of the metallic nature of these materials and the strong spin-orbit coupling of Pt. As a final remark, this strategy is readily extendable to the material screening for thermoelectric generation via the anomalous Nernst effect [40][41][42] and spin Nernst effect [43,44], provided in addition the Mott relation [45] is satisfied.…”