Construction of high performance nanocomposites based on a shape anisotropic soft phase: A micromagnetic simulation study

Abstract

Nanocomposite permanent magnets are considered as a strong candidate for the next generation of high-performance permanent magnet materials due to their ultra-high theoretical magnetic energy product. In this paper, a nanocomposite theoretical model based on the shape anisotropy of the soft phase (Fe65Co35) is constructed to guide the improvement of coercivity, the lack of which has become a critical problem in improving the performance of Nd-Fe-B nanocomposites further. The results of micromagnetic simulation show that adding a shape anisotropic soft phase to nanocomposites can effectively improve coercivity, delay nucleation during the magnetization reversal process, and help obtain a demagnetization curve with high squareness. When the length size of the soft phase ds ≤ 21 nm and the aspect ratio of the soft phase I = 5 for the Nd2Fe14B/Fe65Co35 nanocomposites, almost square demagnetization curves can be obtained, particularly when ds = 21 nm, the size of the soft phase is 21 × 21 × 105 nm3, the content of the soft phase is 42.1 vol. %, and the Nd2Fe14B/Fe65Co35 nanocomposite achieves a maximum magnetic energy product of 94.4 MGOe. In addition, the results also show that, compared with the cubic nanocomposite model ( I = 1), the larger size of the soft phase can be accommodated into the nanocomposites by the addition of shape anisotropy, on the premise of ensuring the soft–hard coupling effect. Our design provides a new strategy and approach for preparing high-performance nanocomposite permanent magnets.

Matching the experimental chemical composition configuration and theoretical model in Nd2Fe14B/α-Fe nanocomposites to improve coercivity

“…3 The nanocomposite magnet, [4][5][6][7][8][9][10] a metamaterial formed by the combination of soft and hard-magnetic phases at the nanoscale, which has an ultra-high theoretical (BH) max value, has become one of the research hotspots of permanent magnetic materials. In addition to high theoretical (BH) max (over 90 MGOe) for Nd 2 Fe 14 B/a-Fe nanocomposites, 11 the addition of a large number of cheap softmagnetic metals/intermetallics in nanocomposite magnets can also effectively reduce the cost of raw materials and save rare earth resources. Moreover, nanoscale grains also endow the nanocom-posite magnets with potential high corrosion resistance, low eddy loss, superior mechanical properties, and other advantages.…”