Nonmagnetic impurities and roughness effects on the finite temperature magnetic properties of core-shell spherical nanoparticles

摘要

Being inspired by a recent study [V. Dimitriadis et al. Phys. Rev. B\textbf{92}, 064420 (2015)], we study the finite temperature magneticproperties of the spherical nanoparticles with core-shell structure includingquenched (i) surface and (ii) interface nonmagnetic impurities (static holes)as well as (iii) roughened interface effects. The particle core is composed offerromagnetic spins, and it is surrounded by a ferromagnetic shell. By means ofMonte Carlo simulation based on an improved Metropolis algorithm, we implementthe nanoparticles using classical Heisenberg Hamiltonians. Particular attentionhas also been devoted to elucidate the effects of the particle size on thethermal and magnetic phase transition features of these systems. Fornanoparticles with imperfect surface layers, it is found that bigger particlesexhibit lower compensation point which decreases gradually with increasingamount of vacancies, and vanishes at a critical value. In view of nanoparticleswith diluted interface, our Monte Carlo simulation results suggest that thereexists a region in the disorder spectrum where compensation temperaturelinearly decreases with decreasing dilution parameter. For nanoparticles withroughened interface, it is observed that the degree of roughness does not playany significant role on the variation of both the compensation point andcritical temperature. However, the low temperature saturation magnetizations ofthe core and shell interface regions sensitively depend on the roughnessparameter.