交换分裂作为铁磁体中巨大反常霍尔与能斯特效应的描述符
Exchange splitting as a descriptor for giant anomalous Hall and Nernst effects in ferromagnets
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中文总结 AI 辅助
本研究以2251种化学取代的四方L1₀合金为对象，发现母体化合物的交换分裂是调控巨大贝里曲率驱动输运响应的关键描述符，预测了两种合金的巨大反常输运响应值。
中文摘要 AI 辅助
反常霍尔效应（AHE）与反常能斯特效应（ANE）分别描述磁性材料的横向电响应与热电响应，在自旋电子学及能量收集应用中颇具潜力。本研究采用高通量第一性原理计算，对2251种化学取代的四方L1₀合金展开研究。铁磁体中，增强的响应优先出源于具有小交换分裂的母体化合物衍生合金：作为典型L1₀铁磁体的FePt衍生合金无一种达到高响应区间，而NiPt与CoIr衍生合金大量处于该区间。小交换分裂使多数自旋与少数自旋能带靠近费米能级，为化学取代提供更多机会以调控费米能级附近的能带交叉并放大贝里曲率。研究预测(Co₀.₈Fe₀.₂)(Ir₀.₇Pt₀.₃)具有2809 S·cm⁻¹的巨大反常霍尔电导率，(Ni₀.₈Co₀.₂)(Pt₀.₇Ir₀.₃)具有7.72 A·m⁻¹·K⁻¹的巨大反常能斯特电导率。研究结果将母体化合物的交换分裂确定为化学可调性的描述符，可用于获取贝里曲率驱动的巨大输运响应。
英文摘要
The anomalous Hall effect (AHE) and anomalous Nernst effect (ANE), which describe transverse electrical and thermoelectric responses in magnetic materials, respectively, are promising for spintronic and energy-harvesting applications. Here, we employ high-throughput first-principles calculations to investigate 2251 chemically substituted tetragonal $L1_0$ alloys. Among ferromagnets, enhanced responses emerge preferentially in alloys derived from parent compounds with small exchange splitting: no alloy derived from FePt, the archetypal $L1_0$ ferromagnet, reaches the high-response regime, whereas NiPt- and CoIr-derived alloys occupy it in large numbers. Small exchange splitting keeps majority- and minority-spin bands near the Fermi level, giving chemical substitution more opportunity to modify near-Fermi-level band crossings and amplify the Berry curvature. We predict a giant anomalous Hall conductivity of $2809\,\mathrm{S\,cm^{-1}}$ in (Co$_{0.8}$Fe$_{0.2}$)(Ir$_{0.7}$Pt$_{0.3}$) and a giant anomalous Nernst conductivity of $7.72\,\mathrm{A\,m^{-1}\,K^{-1}}$ in (Ni$_{0.8}$Co$_{0.2}$)(Pt$_{0.7}$Ir$_{0.3}$). Our results identify the exchange splitting of the parent compound as a descriptor for chemical tunability toward giant Berry-curvature-driven transport responses.
