Colloidal stability in magnetic fluids: effects of the intrinsic dipolar magnetic field in magnetic semiconductors

The effects of the intrinsic dipolar magnetic field on the energy levels and charge density distribution of a spherical magnetic semiconductor nanoparticle have been investigated in the framework of quantum mechanics using the finite element method. It was found that the dipolar magnetic field not only removes the degeneracy of the energy levels, resulting in a redistribution of carriers, but also directly changes the charge density distribution, leading to a modification of the surface charge density with a strong influence upon the colloidal stability. These effects strongly depend on both the nanoparticle magnetization value and the nanoparticle size. The bigger the nanoparticles, the larger the effects of the intrinsic dipolar magnetic field upon the charge density distribution