Radio Frequency Probe Studies of Magnetic Nanostructures

Precise mapping of fundamental parameters like the anisotropy and switching fields is essential to understand the influence of the relaxation, interactions and other phenomena that govern the dynamic magnetic properties in magnetic nanostructures. Dynamic transverse susceptibility ([[Chi].sub.T]) experiments provide a very sensitive and unique way to probe these features. Using a sensitive resonant method based on a radio frequency (RF) tunnel-diode oscillator (TDO), we have, for the first time, mapped the complete variation of [[Chi].sub.T] in the H-T plane in several nanoparticle systems covering the superparamagnetic and blocked regimes. The variation is described well using theoretical models taking into account the thermal relaxation and anisotropy field distribution. Index Terms--Magnetic anisotropy, nanoparticle, superparamagnetism, transverse susceptibility.