Hysteresis of the Magnetic Particle in a Dipolar Ising Model**The project supported by National Natural Science Foundation of China (Grant No. 10174049) and the Natural Science Foundation of Jiangsu Education Committee of China (Grant No. 00KJB140009)

Abstract

Zero-temperature Monte Carlo simulations are used to investigate the hysteresis of a magnetic particle in a dipolar Ising model. The magnetic particle is described in a system of permanent dipoles, and the dipoles are located in a cubic lattice site. The effects of the shape and the size of the particle on the hysteresis loop at zero temperature are obtained. For strong exchange interactions, the shapes of magnetic hysteresis loops approach rectangle. For weak exchange interactions, the effects of the size and the shape of the particle on the loops are more remarkable than those of strong exchange interactions case. The slope of the hysteresis loop decreases with the increase of the ratio of the semi major axis to the semi minor axis of the ellipsoidal magnetic particle, and there is an increase of the slope of the hysteresis with the decrease of the size of the magnetic particle. The effects of the shape and size of the particle on the coercive force at zero temperature are also investigated.