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Updated: Aug 15, 2025

Optimizing Magnetic Force Microscopy Resolution and Sensitivity to Visualize Nanoscale Magnetic Domains
Published on: July 20, 2022
Decoupling the Characteristics of Magnetic Nanoparticles for Ultrahigh Sensitivity
Mohammad Suman Chowdhury1, Enja Laureen Rösch1, Daniel Arenas Esteban2
1Institute for Electrical Measurement Science and Fundamental Electrical Engineering and Laboratory for Emerging Nanometrology (LENA), TU Braunschweig, Hans-Sommer-Str. 66, 38106 Braunschweig, Germany.
Abstract:
Immunoassays exploiting magnetization dynamics of magnetic nanoparticles are highly promising for mix-and-measure, quantitative, and point-of-care diagnostics. However, how single-core magnetic nanoparticles can be employed to reduce particle concentration and concomitantly maximize assay sensitivity is not fully understood. Here, we design monodisperse Néel and Brownian relaxing magnetic nanocubes (MNCs) of different sizes and compositions. We provide insights into how to decouple physical properties of these MNCs to achieve ultrahigh sensitivity. We find that tricomponent-based Zn0.06Co0.80Fe2.14O4 particles, with out-of-phase to initial magnetic susceptibility χ″/χ0 ratio of 0.47 out of 0.50 for magnetically blocked ideal particles, show the ultrahigh magnetic sensitivity by providing a rich magnetic particle spectroscopy (MPS) harmonics spectrum despite bearing lower saturation magnetization than dicomponent Zn0.1Fe2.9O4 having high saturation magnetization. The Zn0.06Co0.80Fe2.14O4 MNCs, coated with catechol-based poly(ethylene glycol) ligands, measured by our benchtop MPS show 3 orders of magnitude better particle LOD than that of commercial nanoparticles of comparable size.
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