The detection of magnetic gradient aided by correlated random walk

We propose a novel method for sensing the gradient direction of a weak magnetic field overwhelmed by a noisy background through studying the correlated random walk of Brown particles that carry with magnetic moment. Using numerical simulation, we find that the snapshot of the distribution of Brown particles that touched the top surface of a cubic container provides useful information, i.e., the center of the distribution pattern will deflect towards the direction of magnetic gradient. We also find that the impact of magnetic noise can be effectively suppressed by the presence of correlation when the concentration of Brown particles is in the region of $0.2{\rho }_0<\rho <0.7{\rho }_0$. Our findings may motivate novel scheme to identify the direction of magnetic gradient in the presence of strong noise, which is undoubtedly important for practical applications.