Effect of particle size distribution on magnetic behavior of nanoparticles with uniaxial anisotropy

The effect of particle size distribution on the field and temperature dependence of the hysteresis loop features like coercivity (H_C), remanence (M_R), and blocking temperature (T_B) is simulated for an ensemble of single domain ferromagnetic nanoparticles with uniaxial anisotropy. Our simulations are based on the two-state model for T<T_B and the metropolis Monte-Carlo method for T>T_B. It is found that the increase in the grain size significantly enhances H_C and T_B. The presence of interparticle exchange interaction in the system suppresses H_C but causes M_R to significantly increase. Our results show that the parameters associated with the particle size distribution (D_d,δ) such as the mean particle size d and standard-deviation δ play key roles in the magnetic behavior of the system.