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Updated: Jan 8, 2026

Optimizing Magnetic Force Microscopy Resolution and Sensitivity to Visualize Nanoscale Magnetic Domains
Published on: July 20, 2022
Low-Intensity Magnetic-Field-Directed Lattice Symmetry Transition to Induce the Centered Rectangular Cylinders in
Wen-Hong Li1, Wen-Sheng Chiu1, Che-Yi Chu1
1Department of Chemical Engineering, National Chung Hsing University, Taichung 402, Taiwan.
Abstract:
This study demonstrates a strategy to control lattice symmetry in a polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer hybridized with a small fraction of NH2-tethered Fe3O4 magnetic nanoparticles incorporated within the cylindrical PMMA microdomains. A low-intensity magnetic field (= 350 mT) was applied following large-amplitude oscillatory shear alignment, transforming the shear-aligned hexagonally packed cylinders (HEX) into centered rectangular cylinders (CR) stabilized through microdomain reorientation that relieved chain crowding and stretching of the PS blocks. In contrast, applying the magnetic field to unoriented HEX induced reorganization into lamellae aligned parallel to the field. The lamellar phase represented the thermodynamic equilibrium state, whereas the CR phase was a kinetically stabilized metastable structure governed by the prealigned framework. These findings highlight low-intensity magnetic manipulation as an effective "noncontact tweezer" for tuning lattice symmetry in block copolymers via the interplay of magnetic anisotropy and initial microdomain orientation.
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