Magnetic-ordering temperature of cobalt/nickel bimetallic nanoparticles: a Monte Carlo investigation.

Temperature-dependent magnetization of core-shell and alloy nanoparticles of cobalt (Co)/nickel (Ni) is investigated within the context of the classical spin Hamiltonian and Monte Carlo simulations. The results of our study indicate that the average temperature-dependent magnetization and magnetic-ordering temperature have a significant influence from variations in the core-shell ratio and chemical order in core-shell nanoparticles. Also, the alloy fraction of Co(Ni) strongly influences the magnetic ordering temperature of the nanoparticles. It is noticed that in alloy nanoparticles, the rise of the magnetic ordering temperature with the increase in Co proportion is linear. However, the same is not true for core-shell nanoparticles where the magnetic-ordering temperature deviates from the straight line fit of alloy T c . It is ascertained that core-shell Co@Ni and Ni@Co nanoparticles sustain higher temperatures in their ferromagnetic state. In the ferrimagnetic nanoparticles, there is a reduction in the saturation magnetization and a display of compensation behavior. [ABSTRACT FROM AUTHOR]