Dipolar Interaction in Magnetic Nanoparticle Systems: A Monte Carlo Study

doi:10.19596/j.cnki.1001-246x.7845

Abstract

Abstract: Dipolar interactions of monodispersed single-domain Fe nanoparticles distributed in simple cubic lattice with different distribution of easy axes are studied with Monte Carlo method. Characteristic parameters of hysteresis loops and zero field cooled(ZFC)/field cooled(FC) magnetization curves are obtained. It is found that blocking temperature (T_B) increases and peaks of ZFC curves are broaden with increasing strength of dipolar interaction. It means that dipolar interactions increase height of effective energy barrier and broaden distribution of effective energy barrier of systems. Reciprocals of FC magnetizations as function of temperature shown that the curves follow Curie-Weiss law well above T_B. Curie-Weiss temperature (T₀) is zero for non-interacting system while it is negative for dipolar interacting system. Negative T₀ indicates that there is antiferromagnetic order in the interacting systems. Furthermore, with increasing strength of dipolar interaction, absolute value of T₀ for interacting system increases. Below blocking temperature, Hysteresis loops show that coercivity and remanence depend strongly on dipolar interaction. It is revealed that strong dipolar interactions suppress both coercivity and remanence of densely packed nanoparticles. Magnetization curves of superparamagnetic systems show that they are depressed with increasing particle packing density. Magnetization curves do not follow Langevin function and exhibit predominantly demagnetizing interacting effect. For interacting systems with 45° angle of applied field with easy axes, height of effective energy barrier are higher than those of random distribution systems, and distribution of effective energy barrier is wider than those of random distribution systems.

Key words: magnetic nanoparticle, dipolar interaction, Monte Carlo method, Heisenberg model

CLC Number:

O469
O737

MO Kangxin, SU Jiajia. Dipolar Interaction in Magnetic Nanoparticle Systems: A Monte Carlo Study[J]. CHINESE JOURNAL OF COMPUTATIONAL PHYSICS, 2019, 36(3): 335-341.

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