Two-step relaxation process of colloidal magnetic nanoclusters under pulsed fields

We empirically uncovered a two-step process of a temporal magnetization response under a pulsed field, which was observed by delaying the particle kinetics in a viscous medium. The Brownian alignment of the magnetization easy-axis appeared to occur separately after the rotated moments reached equilibrium, instead of randomly mixed relaxation behavior. The effective cluster moment and anisotropic magnetopotential difference are two key factors for determining each contribution to the steady-statemagnetization. This finding adds new insight to the understanding of colloidal magnetic nanoclusters as a semi-rigid dipole system, which has potential applications in biomedical platforms. (c) 2018 The Japan Society of Applied Physics