Year: 2024
Type: preprint
Abstract: We use soft x-ray vector-ptychographic tomography to determine the three-dimensional magnetization field in superparamagnetic nanoparticles self-assembled at the liquid-liquid interface and reveal the magnetic order induced by layered structure. The spins in individual nanoparticles become more aligned with increasing number of layers, resulting in a larger net magnetization. Our experimental results show a magnetic short-range order in the monolayer due to the proliferation of thermally induced magnetic vortices and a magnetic long-range order in the bilayer and trilayer, stemming from the strengthened dipolar interactions that effectively suppress thermal fluctuations. We also observe a screening effect of magnetic vortices and the attractive interaction between the magnetic vortices with opposite topological charges. Our work demonstrates the crucial role of layered structure in shaping the magnetization of nanoparticle assemblies, providing new opportunities to modulate these properties through strategic layer engineering.
Authors: Lu, Xingyuan, Zou, Ji, Pham, Minh, Rana, Arjun, Liao, Chen-Ting, Subramanian, Emma Cating, Wu, Xuefei, Lo, Yuan Hung, Bevis, Charles S., Karl, Robert M., Lepadatu, Serban, Yu, Young-Sang, Tserkovnyak, Yaroslav, Russell, Thomas P., Shapiro, David A., Kapteyn, Henry C., Murnane, Margaret M., Streubel, Robert, Miao, Jianwei
Institutions: California NanoSystems Institute, University of California, Los Angeles, Joint Institute for Laboratory Astrophysics, University of Colorado Boulder, University of Colorado System, University of Massachusetts Amherst, University of Lancashire, Lawrence Berkeley National Laboratory, Advanced Light Source
Language: English
Subfield: Biomedical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W4390572885