DETERMINATION OF PARTICLE-SIZE DISTRIBUTION AND CORRELATION OF PARTICLES IN FERROFLUIDS UNDER THE INFLUENCE OF MAGNETIC-FIELDS

Particle size distribution, structure, and magnetic correlations of magnetite particles in ferrofluids are studied with X-ray diffraction methods and electron microscopy. The accordance of the size distributions obtained from small-angle X-ray scattering (SAXS), wide angle X-ray diffraction (XRD), and transmission electron microscopy (TEM) is demonstrated. Under the influence of a magnetic field the particles of ferrofluids aggregate to oblong and directed particle clusters. They have a small extension in field direction, caused by a wide size distribution and the high thermal energy of the particles. The ferrofluids described here are suitable to simulate the crystallographic situation of the Finemet alloys in the state of best soft magnetic properties.