Magnetization Switching of Single Magnetite Nanoparticles Monitored Optically
Nano Letters, vol. 24, pp. 9861–9867
Abstract
High Resolution Image Download MS PowerPoint Slide Magnetic nanomaterials record information as fast as picoseconds in computer memories but retain it for millions of years in ancient rocks. This exceedingly broad range of times is covered by hopping over a potential energy barrier through temperature, ultrafast optical excitation, mechanical stress, or microwaves. As switching depends on nanoparticle size, shape, orientation, and material properties, only single-nanoparticle studies can eliminate the ensemble heterogeneity. Here, we push the sensitivity of photothermal magnetic circular dichroism down to individual 20 nm magnetite nanoparticles. Single-particle magnetization curves display superparamagnetic to ferromagnetic behaviors, depending on the size, shape, and orientation. Some nanoparticles undergo thermally activated switching on time scales of milliseconds to minutes. Surprisingly, the switching barrier varies with time, leading to dynamical heterogeneity, a phenomenon familiar in protein dynamics and supercooled liquids. Our observations will help to identify the external parameters influencing magnetization switching and, eventually, to control it, an important step for many applications.
Authors 7
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Affiliation as printed
Huygens-Kamerlingh Onnes Laboratory, Leiden University; 2300 RA Leiden, The Netherlands
2300 RA Leiden, The Netherlands
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Yonghui Wang Aachen
Leiden University · Harbin Institute of Technology
Affiliation as printed
Huygens-Kamerlingh Onnes Laboratory, Leiden University; 2300 RA Leiden, The Netherlands
School of Mechatronics Engineering, Harbin Institute of Technology; Harbin 150001, People’s Republic of China
2300 RA Leiden, The Netherlands
Harbin 150001, People's Republic of China
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Patrick Spaeth Aachen
Affiliation as printed
Huygens-Kamerlingh Onnes Laboratory, Leiden University; 2300 RA Leiden, The Netherlands
2300 RA Leiden, The Netherlands
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Institute for Atomic and Molecular Physics
Affiliation as printed
Department of Sustainable Energy Materials, AMOLF; Science Park 104, 1098 XG Amsterdam, The Netherlands
Department of Sustainable Energy Materials, AMOLF
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Institute for Atomic and Molecular Physics
Affiliation as printed
Department of Sustainable Energy Materials, AMOLF; Science Park 104, 1098 XG Amsterdam, The Netherlands
Department of Sustainable Energy Materials, AMOLF
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Harbin Institute of Technology
Affiliation as printed
School of Mechatronics Engineering, Harbin Institute of Technology; Harbin 150001, People’s Republic of China
Harbin 150001, People's Republic of China
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Affiliation as printed
Huygens-Kamerlingh Onnes Laboratory, Leiden University; 2300 RA Leiden, The Netherlands
2300 RA Leiden, The Netherlands
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