Dynamic Susceptibility of Ferrofluids: The Numerical Algorithm for the Inverse Problem of Magnetic Granulometry

The size-dependent properties of magnetic nanoparticles (MNP) are the major characteristics, determining MNP application in modern technologies and bio-medical techniques. Direct measurements of the nanosized particles, involved in intensive Brownian motion, are very complicated; so the correct mathematical methods for the experimental data processing enable to successfully predict the properties of MNP suspensions. In the present paper, we describe the fast numerical algorithm allowing to get the distribution over the relaxation time of MNP magnetic moments in ferrofluids. The algorithm is based on numerical fitting of the experimentally measured frequency spectra of the initial dynamic magnetic susceptibility. The efficiency of the algorithm in the solution of the inverse problem of magnetic granulometry is substantiated by the computer experiments for mono- and bi-fractional ferrofluids.

Magnetic Properties Study of Iron Oxide Nanoparticles-Loaded Poly(ε-caprolactone) Nanofibres

Magnetic nanofibres have attracted more and more attention recently due to their possible applications e.g., in spintronics and neuromorphic computing. This work presents the synthesis and physicochemical characterization of the electrospun nanofibres of poly(ε-caprolactone) (PCL) doped by iron oxide nanoparticles with diameters of 5 nm. PCL is a semi-crystalline, hydrophilic polymer showing controllable biodegradation rates, biocompatibility, and flexible mechanical properties. In the composite material, two different concentrations of magnetic nanoparticles were used: 2 and 6 wt.%. PCL-based composites were investigated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetry (TGA). Although in the literature one can find many studies on magnetic polymeric composites, the investigation of their magnetic properties is usually limited to measuring the magnetization curve. Detailed analysis of dynamic magnetic susceptibility is rather rare. In this report, special attention was paid to the detailed analysis of magnetic properties, where we followed the evolution of changes in the magnetic behavior of the material depending on the concentration of magnetic nanoparticles.