Linear composition dependence of the magnetic properties of Gd ₆ Mn ₂₃ alloys with Sm-substitution for Gd

The structure and magnetic properties of the Th6Mn23-type SmxGd6-xMn23 (0 ≤ x < 6) alloys prepared by the induction melting method were studied systematically. The coercivity of the SmxGd6-xMn23 alloys increases near-linearly with increasing Sm content, owing to the enhanced anisotropy field after Sm-substitution. The Curie temperature TC of SmxGd6-xMn23 decreases almost linearly with increasing x in the temperature range of TC ∼ 480 K for x = 0 and TC ∼ 435 K for x = 5.5, owing to the effect of increasing lattice parameters and possibly non-negligible Gd-/Sm–Mn magnetic interactions. The saturation magnetisation of the SmxGd6-xMn23 alloys decreases almost linearly with increasing x (0.5 ≤ x ≤ 5.5), due to the antiferromagnetic coupling of the Sm and Mn moments. The near-linear composition dependence of the coercivity, the Curie temperature and the saturation magnetisation of the SmxGd6-xMn23 alloys indicates substantial Sm-substitution to Gd atoms in the SmxGd6-xMn23 alloys. This work provides a method to tune the magnetic properties of R6Mn23 alloys in a controllable way.