Brownian Relaxation of Interacting Magnetic Nanoparticles in a Colloid Subjected to a Pulsatile Magnetic Field

We have investigated and modeled the effect of interaction among magnetic particles and the magnitude and duration of external applied magnetic field on Brownian relaxation in a colloidal suspension. In the case of interacting magnetic particles, Brownian relaxation depends on the interparticle dipole–dipole interaction, which slows down the overall Brownian relaxation process of magnetic particles in the colloidal suspension. The individual magnetic particle experiences torque when a pulsatile magnetic field is applied. The torque due to the external field randomizes the particle rotation similar to that of the thermal energy. A faster Brownian relaxation is observed when individual magnetic particles are magnetized for a short duration. Magnetizing the magnetic particle for a longer duration suppress the rotational motion hence the effect of torque on Brownian relaxation.