Crystal structure and magnetic properties of CeFe11M (M = Mo, W)

Abstract

Tetragonal CeFe₁₁Mo (struct. type ThMn₁₂, a = 8.529(1) Å, c = 4.766(1) Å, V = 346.68(1) ų) and novel isostructural CeFe₁₁W (a = 8.539(1) Å, c = 4.754(1) Å, V = 346.62(1) ų) are obtained in bulk, as homogenized single-phase arc-melted alloys. Their crystal structures are evaluated by full profile Rietveld analysis of the powder X-ray diffraction patterns which confirm that Ce occupies the 2a atomic site in both cases, whereas atomic disorder is present in the Fe-sublattice, i.e., predominantly on the dumbbell 8i site and minorly on two other sites 8j and 8f. In CeFe₁₁Mo the third element, M, is mixed with Fe on the 8i dumbbell site and 8f atomic position, whereas in CeFe₁₁W, M is mixed on the 8i and 8j Fe sites. In these bulk CeFe_12-xM_x alloys the tetragonal structure persists at lower M content, x  < 1 here, in comparison to known similar alloys, with x  > 1. Because of the low M content, comparably higher values of mass magnetization and Curie temperature are achieved i.e., CeFe₁₁Mo: ϭ_s = 104 emu/g (14.7 µ_B/f.u.), T_c = 420 K and CeFe₁₁W: ϭ_s = 99 emu/g (16.5 µ_B/f.u.), T_c = 450 K. Magnetocrystalline anisotropy is uniaxial with anisotropy fields H_a ∼ 14.5 and 16.5 kOe, respectively. Based on Curie temperature and magnetic anisotropy enhancements, using tungsten as the stabilizing dopant is more beneficial than molybdenum.