Magnetic characterization of the (Zr,Sm)Co3 phase in Sm(CoFeCuZr)z magnets

Abstract

Magnets with composition Sm(CobalFe0.2Cu0.1Zrx)8 (x=0;0.02;0.04;0.06,0.08) were studied using x-ray diffraction Rietveld analysis. In addition to the majority 2:17 and 1:5 phases, the magnets present a rhombohedral (SmZr)1(CoFeCu)3 (PuNi3 structure) phase, whose volume fraction increases with Zr addition. Higher Zr contents decrease coercivity and lead to the appearance of impurity phases such as 6:23 (Th6Mn23 structure), 2:7R (Gd2Co7 structure), and 5:19R (Ce5Co19 structure) in the magnets. The 1:3R phase was reproduced in a Fe57-doped sample of Sm0.33Zr0.67Co3 and its Mössbauer spectra, at several temperatures, were adjusted using four sextets and a nonmagnetic doublet. The beneficial effect of small additions of Zr on the coercivity of the magnets is discussed.

Interacting Stoner–Wohlfarth behavior in hysteresis curves of Sm(CoFeCuZr)z magnets

“…XRD Rietveld allowed the identification of cubic 6:23 (Zr,Sm) 6 (Co,Fe) 23 , rhombohedral (SmZr) 5 (CoFeCu) 19 , rhombohedral (SmZr) 2 (CoFeCu) 7 , rhombohedral (SmZr) 1 (CoFeCu) 3 as the more relevant Zr-rich impurity phases. …”

“…This result can be attributed to the presence of grains of Zr-rich impurity phases [9], which are presumably softer and generate stray fields that could provoke magnetic reversal of the 2:17 nanograins. Microstructural analysis was carried out to determine the nature of these impurity phases [6,7,9]. The results obtained from scanning electron microscopy (SEM) [9] indicated the presence of several phases with the sum Sm+Zr ranging from 15 to 25 at%.…”

“…The results obtained from scanning electron microscopy (SEM) [9] indicated the presence of several phases with the sum Sm+Zr ranging from 15 to 25 at%. Rietveld analysis of X-ray diffraction (XRD) spectra [6,7] was then employed, and the results from both SEM and Rietveld XRD are summarized as follows.…”

“…The commercial alloys are, in fact, fiveelement alloys, with composition based on Sm 2 Co 17 phase with additions of Cu, Fe and Zr. The microstructure of the SmCo 2:17 magnets is nanocrystalline and has three main phases, all of them crystallographically coherent: the cell phase Sm 2 (Co,Fe) 17 , the cell boundary phase Sm(Co,Cu) 5 and the lamellar or platelet phase (ZrSm) 1 (CoFeCu) 3 with PuNi 3 structure [6,7] (also described as BeNb 3 structure [8])…”

Microstructural changes during the slow-cooling annealing of nanocrystalline SmCo 2:17 type magnets

“…6. The 1:3 phase has been described as Rhombohedral Sm 1 Zr 2 Co 9 , a stable phase in the ternarium Sm-Zr-Co, with structure derived from PuNi 3 [30][31][32], see Table 1. The X-ray spectra of the 820°C sample and 400°C sample are very similar, both with $7% of nanocrystalline Sm(CuCu) 5 phase (crystallite size $12 nm), 3% of 1:3 and all the rest 2:17R (crystallite size $50 nm provided best fitting in the Rietveld analysis).…”