Blocking temperature in nanocrystalline systems with “alloy-like” ferromagnetic–antiferromagnetic heterogeneous morphology

Abstract

A modified Monte Carlo Metropolis method is performed to simulate the blocking temperature (TB) in an “alloy-like” ferromagnetic(FM)x–antiferromagnetic(AFM)1−x heterogeneous system with geometrical frustration. It is found that the blocking temperature, at which the field-cooled (FC) and zero-field-cooled (ZFC) magnetization curves are splitting, changes little for x≤0.5 initially, then decreases obviously with the increase in x. Some discrete error bars emerge for large x owing to the superparamagnetic or agglomerate behavior of the small antiferromagnet. Using a thermal fluctuation model, an analytic expression for TB as a function of x is obtained. By calculating the curves of temperature derivative of the difference between FC and ZFC magnetizations and analyzing the distribution of energy barriers, we interpret the dependence of TB on different proportions of ferromagnetic phase in detail.