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FePt/Co core/shell nanoparticle-based anisotropic nanocomposites and their exchange spring behavior
Deyao Li1, Hui Wang, Zhenhui Ma
1School of Materials Science and Engineering, Beihang University, Beijing 100191, P.R. China. tlzhang@buaa.edu.cn jiangcb@buaa.edu.cn.
Nanoscale
|February 13, 2018
Summary
Aligned FePt/Co core/shell nanoparticles create new anisotropic nanocomposites. These materials show exchange spring behavior, where cobalt shells reverse before platinum-iron cores, paving the way for advanced permanent magnets.
Area of Science:
- Materials Science
- Nanotechnology
- Magnetism
Background:
- Anisotropic exchange-coupled nanocomposites are promising for next-generation permanent magnets.
- Previous studies primarily focused on thin films or bulk materials, leaving the effect of easy-axis alignment on exchange coupling unclear.
Purpose of the Study:
- To synthesize and align FePt/Co core/shell nanoparticles to create anisotropic nanocomposites.
- To investigate the impact of easy-axis alignment on exchange coupling and magnetic properties.
Main Methods:
- Seed-mediated synthesis of FePt/Co core/shell nanoparticles.
- Alignment of nanoparticles using an external magnetic field and fixation in an acrylic binder.
- Magnetic property characterization, including hysteresis loop analysis and remanence ratio determination.
Main Results:
- Successfully synthesized strongly coupled FePt/Co core/shell nanoparticles with single-phase-like hysteresis loops.
- Achieved a high degree of orientation in anisotropic nanocomposites, increasing the remanence ratio from 0.62 to 0.78.
- Observed a kink in the demagnetization curve, indicating exchange spring behavior where Co shells reverse before FePt cores.
Conclusions:
- Aligned FePt cores create a stronger dipolar field in Co shells, causing them to reverse at lower fields.
- The study provides a new method for preparing anisotropic hard/soft-phase nanocomposites.
- Findings offer insights for designing high-performance anisotropic exchange-coupled nanocomposites.
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