Magnetic and structural characteristics of PrCo13−xSix alloys and their nitrides

Abstract PrCo 13− x Si x alloys with 0 ≤ x ≤ 4.5 have been synthesized and studied at temperatures from 1 0 to 1273 K and in fields up to 17 kOe. The structure and magnetic properties of the alloys vary significantly with changes in Si content x . In the alloys with x = 0, TMA and XRD studies show the phases present to be Pr 2 Co 17 and Co. For x = 1.5 or 2.0, the alloys are essentially single-phase fcc materials (NaZn 13 structure type). At larger values of x the ternary alloy formed in a bct structure (Ce 2 Ni 17 Si 9 structure type). Replacement of Co by Si in PrCo 13 results in a drop in T C from 1318 K (for LaCo 13 ) to ∼ 900 K for fcc Pr(Co,Si) 13 alloy and to ∼ 20 K for bct Pr(Co,Si) 13 alloys. There is also a large drop in magnetization from 104.6 emu/g for the alloy with x = 1.5 to 19.2 emu/g for the alloys with x = 4.0. A bct alloy ( x = 3.5) showed negligible magnetic anisotropy. Si doping sharply reduces the Co moment. Si doping also reduces the Pr moment to 1.5μ B (fcc alloys) and to 1.8μ B (bct alloys). Nitrogenation fails to improve Pr(Co,Si) 13 alloys as permanent magnet materials.