Structure and permanent magnet properties of Zr1-xRxFe10Si2 alloys with R = Y, La, Ce, Pr and Sm

• ThMn12-type Zr0.7R0.3Fe10Si2 structure forms with Y, Ce, Pr, Sm, but not with La.
• 30% Sm substitution for Zr increases the anisotropy field by 120%.
• The Zr0.7Sm0.3Fe10Si2 compound has a magnetic hardness parameter of 1.3.
• The effect of Sm is confirmed in melt-spun nanocrystalline alloys.

Arc-melted (Zr0.7R0.3)1.1Fe10Si2 alloys with R = Y, Ce, Pr and Sm crystallize into the ThMn12-type structure; La substitution leads to the formation of a separate NaZn13-type phase. Compared to the rare-earth-free parent compound, Y, Ce and Sm strengthen the magnetocrystalline anisotropy in this order; whereas Pr weakens it. The effect of Sm is by far the strongest; an anisotropy field of 40.7 kOe determined for the Zr0.7Sm0.3Fe10Si2 by the singular point detection technique is high enough to make this compound a good candidate for a very rare-earth-lean, cobalt-free permanent magnet material. The effect of Sm has been demonstrated in isotropic nanocrystalline alloys prepared via melt-spinning followed by vacuum annealing. The optimally processed alloys with R represented by Zr and Sm exhibited coercivity values of 0.7 and 2.4 kOe, respectively. The analysis suggests that the development of the coercivity is controlled by decomposition of the 1:12 structure in the former sample and by the crystallite growth in the latter. Calculated remanence and maximum energy product of the Sm-substituted nanocrystalline alloy were 6.3 kG and 4.6 MGOe. The cubic Zr6Fe16Si7 compound, which is the frequent minority phase in the studied alloys, was also synthesized and found to be paramagnetic at the room temperature.

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