Spectra of the Effects of Magnetic Birefringence and Dichroism in Magnetic Colloids with Different Particle Sizes

Abstract

An experimental study is performed of the spectral dependences of effects of birefringence and dichroism in magnetic colloids with magnetite nanoparticles that have average sizes of 5.5 and 8 nm. It is shown that the magnitude of the effects in a sample with larger particles is approximately twice as high at identical volume concentrations. Possible reasons for this difference are analyzed with respect to the polydis- persity of the samples, and to the possibility of their having magnetically hard and superparamagnetic parti- cles. Calculations of the spectra of the effects of birefringence and dichroism are in good agreement with the experimental data.