Comparative study of finite temperature demagnetization in Nd2Fe14B and SmCo5 based hard-soft composites

Abstract

We study with finite temperature Monte Carlo simulation under periodic boundary conditions the demagnetization behavior of exchanged-coupled hard/soft magnets composed of hard cube inclusions (Nd2Fe14B, or SmCo5) in a soft (FeCo) matrix. The easy axis of the hard and soft phases are parallel to the applied field. We study the effect of finite temperature and the soft phase content on the coercivity, the remanence, and the energy product of the composites. We find that because of the difference in magnetization between the two phases, to lower the dipolar energy the magnetization of the two phases is not completely parallel to each other. This results in a much smaller increase of the remnant magnetization with increasing the soft magnet content than anticipated, especially at higher temperatures. This, together with the lower coercivity of Nd2Fe14B, greatly affects the energy product in Nd2Fe14B/FeCo in comparison with SmCo5/FeCo. We underline the essential difference in the induction dependence on the applied field in these compounds.

Applications of exchange coupled bi-magnetic hard/soft and soft/hard magnetic core/shell nanoparticles

“…Interestingly, in the case of the SmCo-Fe system, using periodic boundary conditions, the conventional SmCo/Fe core/shell nanoparticles seem to have improved properties with respect to the inverse Fe/SmCo ones [230]. Moreover, some studies on spherical soft magnetic inclusions embedded in a hard matrix, hard/soft nanoparticles embedded in a hard matrix, soft/hard nanoparticles embedded in a soft matrix, or hard inclusions in a soft matrix can be found in the literature [224,[232][233][234][235][236][237][238][239][240]. The results show that the magnetic properties are strongly influenced by the dimensions and shape of the inclusions [224,[232][233][234]240].…”

The coercive behavior and the energy product for multilayers of FeCo and Sm–Fe–N

“…For actual design of the optimal magnet it is important to have quantitative information about different possible systems. In our recent simulation results for hard cube inclusions in a soft matrix [3] we found magnetic charges at the hard soft interface which results in a tilting of the soft magnetization. The multilayer structure is the most favorable from the magnetostatic point of view because the alignment soft and hard phase spins parallel to the layers do not create surface magnetic charges.…”

Effect of exchange coupling on magnetic property in Sm–Co/ α -Fe layered system

“…Since an exchange-coupled composite material was proposed by Kneller in 1991, [1] with a hard phase to provide high coercivity and a soft phase to provide high saturation and remanence, the coercivity, structural, and magnetic properties in permanent magnets have always been an important topic in magnetism. [2][3][4] An energy product paradox was proposed in some literatures, which has been intensively studied in both experimental [5][6][7][8] and theoretical [9][10][11][12][13][14][15] works by condensed matter physicists. A lot of works have been devoted to the exploration of the largest energy product experimentally reachable.…”