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

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. (C) 2011 American Institute of Physics. [doi:10.1063/1.3646474]