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arXiv 2209.04199cond-mat.mtrl-sciphysics.app-ph
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Fe-Ag颗粒多层膜中集体磁性受抑制的证据

Evidence for suppression of collective magnetism in Fe-Ag granular multilayers

László F. Kiss, László Bujdosó, Dénes Kaptás

AI总结:

本文研究Fe-Ag颗粒多层膜中Fe纳米颗粒的偶极相互作用,发现Ag层针孔导致的直接铁磁耦合会抑制超自旋阻挫和超自旋玻璃态,并揭示各向异性能超过阈值时集体磁行为受抑制的机制。

摘要:

在Fe-Ag颗粒多层膜中发现了偶极相互作用的Fe纳米颗粒集体磁行为受到抑制的证据。研究了位于相邻Fe层中的Fe颗粒之间的相互作用,该相互作用作为仅两层Fe层之间Ag层标称厚度的函数。通过记忆效应测量验证,相互作用随Ag层厚度增加而意外增强,这可以通过在较小Ag厚度下Ag层中形成针孔来解释,针孔允许相邻Fe层中的Fe颗粒之间发生直接铁磁耦合,这可能阻碍偶极相互作用所倾向的超自旋阻挫。在较大Ag厚度下,Ag层连续且无针孔,阻挫导致超自旋玻璃态的出现。相互作用增强的效应与低温下测量的场冷(FC)磁化强度相对于基于双能级系统弛豫模型计算的无相互作用FC曲线的偏差随温度降低而增大密切相关。最近发表的一篇论文(Sánchez et al., Small 2022, 18, 2106762)中报道了类似现象,该论文研究了一个致密纳米颗粒系统。当单个颗粒的各向异性能超过某一阈值时,由偶极相互作用引起的颗粒集体磁行为受到抑制。

英文摘要:

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.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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