Magnetic properties and magneto-birefringence of magnetic fluids
M. Rasa
Institute for Complex Fluids, "Politehnica'' University of
Timisoara, Bd. Mihai Viteazul 1, Timisoara 1900, Romania
West University of Timisoara, Faculty of Physics, Bd. V. Parvan
4, Timisoara 1900, Romania
brahma@quasar.uvt.ro
Received 18 July 1999 and Received in final form 13 January 2000
Abstract
Static magnetic properties of a large variety of magnetic fluids
with magnetite particles is studied. A qualitative study of
magnetization curves was performed to establish the influence of
interactions or the presence of agglomerations in each sample.
Improved equations for magneto-granulometric analysis, for ideal
ferrofluids, were proposed. Better results for the mean magnetic
diameter than in the case of using the known equations were
obtained. A quantitative study using several models for ideal and
interacting particles was performed to select the best method and
dimensional distribution function for magneto-granulometric
analysis as well as for accurately determining macroscopic
quantities of samples (initial susceptibility, saturation
magnetization, particle number density or magnetic volume fraction)
and properties of nanoparticles (mean magnetic diameter, thickness
of the nonmagnetic layer and particle distribution). A new model
for magneto-birefringence was proposed and discussed as well as
applied for diluted and concentrated ferrofluids. The Langevin
behaviour of samples was investigated and compared with the
investigation based on magnetic properties. Nanoparticles
parameters like mean "magneto-optical'' diameter, effective
anisotropy constant, Shliomis diameter and the real part of the
electrical permittivity of particles were accurately determined.
PACS
75.50.Mm Magnetic liquids - 75.60.Ej Magnetization curves,
hysteresis, Barkhausen and related effects
- 78.20.Fm Birefringence
Copyright EDP Sciences, Società Italiana di Fisica, Springer-Verlag
