This study explores the impact of external magnetic fields on thermoelectric properties, focusing on the interplay of spin and quantum effects. Using gadolinium (Gd) as a case study, we observed anomalous magneto-thermopower trends, with a reduction in thermopower at ∼35 K and an enhancement at ≈ 293 K under high magnetic fields. Comprehensive temperature and field-dependent measurements, including specific heat capacity, magnetic susceptibility, and Hall effect, were performed to uncover the underlying mechanisms. We derived a relation for the total thermopower of an uncompensated ferromagnetic metal and calculated multi-band carrier characteristics, such as concentration and mobility, using the maximum entropy principle. Our findings reveal a ∼70 % suppression of the magnetic contribution to specific heat capacity under a 12 T field and a positive magnon-drag contribution to the total thermopower. Field-dependent Hall measurements indicate that the anomalous Hall effect is dominated by intrinsic contributions from Berry curvature. Additionally, transverse magnetoresistance data suggest anisotropic Fermi surfaces, domain movement, suppression of spin-flip effects, and Fermi surface modifications. First-principles calculations based on Density Functional Theory (DFT) further support these findings. These calculations reveal significant Berry curvature contributions, leading to an anomalous Hall conductivity of approximately 1260 S/cm at the Fermi level. The enhancement of thermopower near is primarily attributed to the suppression of magnon-drag and the imbalance in carrier mobility and relaxation times, driven by spin and quantum effects. These combined effects result in a ∼50 % increase in thermopower and a ∼150 % improvement in at 12 T. The notable peak in at cryogenic temperatures highlights a potential pathway for designing efficient thermoelectric materials for cryogenic cooling applications. Our results demonstrate the significance of field-dependent spin and quantum effects in enhancing thermoelectric performance, offering new directions for thermoelectric research and material design.

中文翻译：

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磁场相关的热电势：洞察自旋和量子相互作用


本研究探讨了外部磁场对热电性能的影响，重点关注自旋效应和量子效应的相互作用。使用钆 (Gd) 作为案例研究，我们观察到异常磁热电趋势，在高磁场下，热电势在 ∼35 K 处降低，在 ≈ 293 K 处增强。进行了全面的温度和场相关测量，包括比热容、磁化率和霍尔效应，以揭示潜在的机制。我们利用最大熵原理推导了未补偿铁磁金属的总热电势关系，并计算了多带载流子特性，例如浓度和迁移率。我们的研究结果表明，在 12 T 场下，磁对比热容的贡献被抑制约 70%，并且磁振子阻力对总热电势的贡献为正。场相关霍尔测量表明，反常霍尔效应主要由贝里曲率的内在贡献决定。此外，横向磁阻数据表明各向异性费米表面、磁畴移动、自旋翻转效应的抑制和费米表面修饰。基于密度泛函理论 (DFT) 的第一性原理计算进一步支持了这些发现。这些计算揭示了贝里曲率的显着贡献，导致费米能级的异常霍尔电导率约为 1260 S/cm。附近热电势的增强主要归因于自旋和量子效应驱动的磁振子阻力的抑制以及载流子迁移率和弛豫时间的不平衡。这些综合效应导致热电势增加约 50%，并在 12 T 时提高约 150%。 低温下的显着峰值凸显了为低温冷却应用设计高效热电材料的潜在途径。我们的结果证明了场相关自旋和量子效应在增强热电性能方面的重要性，为热电研究和材料设计提供了新的方向。