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Magnetic nanostructures hold tremendous potential as basic
building blocks in spin-electronic devices and high-density data storage.
Precise mapping of fundamental parameters like the anisotropy and
switching fields over a wide range in temperature and magnetic fields, is
essential to understand the influence of the relaxation, interactions and
other phenomena that govern the dynamic magnetic properties in these
systems. Dynamic radio-frequency transverse susceptibility (χT)
experiments provide a very sensitive and unique way to probe these
features. We present and discuss the field-dependent transverse
susceptibility in two nanoparticle systems: (i) polymer-coated Fe
particles and (ii) γ-Fe2O3 particles synthesized by micelle method.
Systematic χT scans at different fixed temperatures reveal variation of
the switching and anisotropy fields. Our experiments provide a unique and
powerful way to precisely probe the dynamic magnetization in the presence
of thermal relaxation and interactions.
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