Micromagnetic simulations of reversal magnetization in cerium-containing magnets

Single-grain models with different cerium contents or structural parameters have been introduced to investigate the reversal magnetization behaviors in cerium-containing magnets. All the micromagnetic simulations are carried out via the object oriented micromagnetic framework (OOMMF). As for single (Nd, Ce)(2)Fe14B type grain, the coercivity decreases monotonously with the increase of the cerium content. Four types of grain structure have been compared: single (Nd, Ce)(2)Fe14B type, core ((Nd, Ce)(2)Fe14B)-shell (Nd2Fe14B) type with 2 nm thick shell, core (Ce2Fe14B)-shell (Nd2Fe14B) type, and core (Nd2Fe14B)-shell (Ce2Fe14B) type. It is found that core ((Nd, Ce)(2)Fe14B)-shell (Nd2Fe14B) type grain with 2 nm thick shell always presents the largest coercivity under the same total cerium content. Furthermore, the relationship between the coercivity and the shell thickness t in core ((Nd, Ce)(2)Fe14B)-shell (Nd2Fe14B) type grain has been studied. When the total cerium content is kept at 20.51 at.%, the analyzed results show that as t varies from 1 nm to 7 nm, the coercivity gradually ascends at the beginning, then quickly descends after reaching the maximum value when t = 5 nm. From the perspective of the positions of nucleation points, the reasons why t affects the coercivity are discussed in detail.