Enhancement of Hard Magnetic Properties in Fraktal-Like Nano and Mesoscopic Grains

Abstract

The paper refers to Monte Carlo magnetic simulations for fractal-like nano and mesoscopic grains. The analyzed objects differed in the size, surface development, magnetic anisotropy and the spin values attributed to the system nodes inside the fractal. Such an approach allowed us to determine their magnetization processes as well as optimization characteristics in the direction to enhancement of hard magnetic properties. As it was shown, the size effects depend on the chosen value of magnetic anisotropy. In the case of fractals with ultra-high coercivity, the decreasing of their size leads to deterioration of coercivity, especially for the high surface to volume ratio. Opposite effects were observed for soft magnetic fractals when the nanostructure caused an appearance of the coercive field, and the maximum of energy product was predictably significantly higher than for conventional rare earths’ free permanent magnets.

High and Ultra-High Coercive Materials in Spring-Exchange Systems—Review, Simulations and Perspective

“…The disorder-based MC algorithm (developed by our team) was used as a computation method [ 45 , 46 ]. It is important that the algorithm allows for simulating the magnetization processes of systems containing magnetically different phases, and it has successfully been used in the study of similar objects [ 47 ]. For a detailed description, see [ 45 ].…”

“…For a detailed description, see [ 45 ]. In addition, the simulation parameters used in this paper are the same as those in [ 47 ].…”

“…According to the Hamiltonian used in our method [ 45 , 47 ], the simulations require establishing the values of the spin S , anisotropy constant K , and exchange integral parameter J, assuming that the nodes are equally spaced at a distance of 1 nm. The spin values were calculated with the assumption that the saturation magnetization of the simulated system is equal to the mass magnetization of the real compound.…”