Size distribution of magnetic nanoparticles estimated from Browninan relaxation in a solution

We measured complex magnetic susceptibility of magnetic nanoparticles in a solution. Analyzing the frequency dependence of the susceptibility with the so-called singular value decomposition (SVD) method, we obtained the size distribution of magnetic nanoparticles in the sample. It was shown that the frequency dependence of the susceptibility reconstructed from the estimated size distribution agrees well with the experimental result. It was also shown that the estimated size distribution reasonably agrees with that obtained from different measurement, i.e., optical dynamic light scattering (DLS). These agreements show the validity of the present method to evaluate the size distribution from magnetic the measurement.