d电子态密度在Pt-Ni和Pt-Pd纳米颗粒量子尺寸效应中的作用
Role of d-electron density of states in the quantum size effect of Pt-Ni and Pt-Pd nanoparticles
浏览论文内容
中文总结 AI 辅助
本研究通过¹⁹⁵Pt核磁共振测量双金属Pt基纳米颗粒的量子尺寸效应，揭示d电子态密度对该效应的关键作用，还发现Ni含量升高会增强铁磁关联并趋近量子临界区。
中文摘要 AI 辅助
我们利用¹⁹⁵Pt核磁共振测量，研究了双金属Pt₁₋ₓPdₓ和Pt₁₋ₓNiₓ纳米颗粒中的量子尺寸效应（QSE）。Pt₁₋ₓPdₓ纳米颗粒中核自旋-晶格弛豫率除以温度的异常量1/T₁T的温度和尺寸依赖性，表明Pt和Pd原子之间具有相似的电子态，且能通过QSE得到很好的解释。1/T₁T和奈特位移的温度及组分变化显示，随着Ni含量增加，态密度系统性升高，特征能标T*降低，这与久保间隙δ_Kubo一致。与QSE被抑制的Pt₁₋ₓCuₓ纳米颗粒不同，Pt₁₋ₓNiₓ纳米颗粒表现出清晰的量子能量离散化特征。这一差异凸显了d电子在QSE显现中的关键作用。此外，对修正的Korringa参数K(α)的分析表明，随着Ni浓度升高，铁磁关联增强，体系趋近于铁磁量子临界区域。这些结果提供了实验证据，证明在由金属性d电子原子构成的纳米颗粒中，d电子态密度对QSE的显现起着至关重要的作用。
英文摘要
We investigated the quantum size effect (QSE) in bimetallic Pt$_{1-x}$Pd$_x$ and Pt$_{1-x}$Ni$_x$ nanoparticles, using $^{195}$Pt nuclear magnetic resonance measurements. The temperature and size dependencies of the anomaly in the nuclear spin-lattice relaxation rate divided by temperature $1/T_1T$ in the Pt$_{1-x}$Pd$_x$ nanoparticles suggest similar electron states between Pt and Pd atoms and are well understood by the QSE. The temperature and composition variations of $1/T_1T$ and Knight shift reveal a systematic increase in the density of states and reduction of the characteristic energy scale $T^*$ with increasing Ni content, consistent with the Kubo gap $δ_{\mathrm{Kubo}}$. In contrast to Pt$_{1-x}$Cu$_x$ nanoparticles where the QSE is suppressed, the Pt$_{1-x}$Ni$_x$ nanoparticles exhibit clear signatures of quantum energy discretization. This discrepancy highlights the essential role of $d$-electrons in the manifestation of the QSE. Furthermore, analysis of the modified Korringa parameter $K(α)$ suggests enhanced ferromagnetic correlations with increasing Ni concentration, approaching a ferromagnetic quantum critical regime. These results provide experimental evidence that $d$-electron density of states plays a crucial role in the manifestation of the QSE in the nanoparticles formed by the metallic $d$-electron atoms.
