Abstract
Magnetization reversal mechanism is found to vary with cellular structures by a comparative study of the magnetization processes of three (Sm, Dy, Gd) (Co, Fe, Cu, Zr)z magnets with different cellular structures. Analysis of domain walls, initial magnetization curves and recoil loops indicates that the morphology of cellular structure has a significant effect on the magnetization process, besides the obvious connection to the difference of domain energy density between cell boundary phase (CBP) and main phase. The magnetization of Sample 2 (with a moderate cell size and uniformly continuous CBPs) behaves as a strong coherence domain-wall pinning effect to the domain wall and lead to a highest coercivity in the magnet. The magnetization of Sample 1 (with thin and discontinuous CBPs) shows an inconsistent pinning effect to the domain wall while that of Sample 3 (with thick and aggregate CBPs) exhibits a two-phase separation magnetization. Both the two cases lead to lower coercivities. A simplified model is given as well to describe the relationships among cellular structure and magnetization behavior.
Highlights
Three (SmDyGd)(CoFeCuZr)z permanent magnets were prepared by liquid phase sintering
With the adding ratios of liquid phase sintering. DyCo0.51 (LP) increasing from 0 to 5 wt%, it can be seen clearly that the cell size decreases significantly from ∼200 nm to ∼100 nm, the thickness of the cell boundary phase (CBP) is monotonously increasing from ∼5 nm to ∼15 nm and the Cu content of the CBP is gradually decreasing
A big cell (∼200 nm) with thin and discontinuous CBP is obtained in the magnet without Dy-Co addition (Sample 1)
Summary
2:17 type SmCo permanent magnet has wide applications especially in high temperature for its large coercive force, excellent thermal stability, high Curie temperature and superior corrosion resistance.[1,2,3] One of the hot topics in 2:17 type SmCo magnet is its coercivity mechanism because of its complex microstructure,[3,4,5] which consists of 2:17 type cells surrounded by a Cu-rich 1:5 cell boundary phase (CPB). It is necessary to illustrate the relationships among cellular structure, magnetization behavior and intrinsic coercivity in 2:17 type SmCo magnets. We have found that Dy-Co liquid phase addition can regulate the microstructure of magnet and adjust its coercivity at the same time.[12] In this paper, the magnetic behavior during magnetization and reversal magnetization process of (Sm, Gd, Dy) (Co, Fe, Cu, Zr)z magnets with adding 0 wt%, 3 wt% and 5 wt% ratios of DyCo0.51 liquid phase, which possess different cellular structures, are deeply discussed
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