论文标题
抑制Fe-ag粒状多层抑制集体磁性的证据
Evidence for suppression of collective magnetism in Fe-Ag granular multilayers
论文作者
论文摘要
在Fe-ag粒状多层中，发现了抑制双极相互作用的Fe纳米颗粒的集体磁性行为的证据。研究位于相邻FE层中的Fe颗粒的相互作用是仅在两个Fe层之间的AG层厚度的函数。通过记忆效应测量值验证的与增加的Ag层厚度的相互作用令人惊讶地增加，这是通过在小Ag厚度下Ag层中的针孔形成的，从而使邻近FE层中Fe颗粒之间的直接铁磁偶联可能阻碍了双极相互作用的susperspins的挫败感。在较大的Ag厚度下，Ag层是连续的，没有针孔，挫败感会导致Superspin-Glass状态的出现。增加相互作用的效果与测得的现场冷却（FC）磁化的低温下的偏差与从模型基于两级系统的松弛计算得出的无相互作用FC曲线的偏差良好相关。在最近发表的论文（Sánchez等人，小2022，18，2106762）中报道了类似的现象，其中研究了密集的纳米颗粒系统。当单个颗粒的各向异性能量超过一定阈值时，由于偶极相互作用引起的颗粒的集体磁性行为被抑制。
Evidence for the suppression of collective magnetic behavior of dipolarly interacting Fe nanoparticles is found in Fe-Ag granular multilayers. Interaction of Fe particles located in neighboring Fe layers is studied as a function of the nominal thickness of the Ag layer in between only two Fe layers. The surprisingly increasing interaction with increasing Ag-layer thickness, verified by memory-effect measurements, is explained by the formation of pinholes in the Ag layer at small Ag thicknesses, allowing direct ferromagnetic coupling between Fe particles in neighboring Fe layers which may hinder the frustration of superspins favored by dipolar interactions. At larger Ag thicknesses, the Ag layer is continuous without pinholes and frustration leads to the appearance of the superspin-glass state. The effect of increasing interactions correlates well with the growing deviation at low temperatures of the measured field-cooled (FC) magnetization from the interaction-free FC curve calculated by a model based on the relaxation of two-level systems. Similar phenomenon is reported in a recently published paper (Sánchez et al., Small 2022, 18, 2106762) where a dense nanoparticle system is studied. The collective magnetic behavior of the particles due to dipolar interactions is suppressed when the anisotropy energy of the individual particles exceeds a certain threshold.
