We report on the synthesis of single-crystal and polycrystalline samples of ${\mathrm{Ce}}_{3-x}{\mathrm{Mg}}_x{\mathrm{Co}}_9$ solid solution ($0\le x\lesssim 1.4$) and characterization of their structural and magnetic properties. The crystal structure remains rhombohedral in the whole composition range and Mg partially replaces Ce in the $6c$ site of the ${\mathrm{CeCo}}_3$ structure. Ferromagnetism is induced by Mg substitutions starting as low as $x=0.18$ and reaching a Curie temperature as high as 450 K for $x=1.35$. Measurements on single crystals with $x=1.34$ and $T_C=440\mathrm{K}$ indicate an axial magnetic anisotropy with an anisotropy field of 6 T and a magnetization of $6{\mu }_B/\mathrm{f}.\mathrm{u}.$ at 300 K. Coercicity is observed in the polycrystalline samples consistent with the observed axial magnetic anisotropy. Our discovery of ferromagnetism with large axial magnetic anisotropy induced by substituting a rare-earth element by Mg is a very promising result in the search of inexpensive permanent-magnet materials and suggests that other nonmagnetic phases, similar to ${\mathrm{CeCo}}_3$, may also conceal nearby ferromagnetic phases.

• Received 31 October 2017
• Revised 16 January 2018

DOI:https://doi.org/10.1103/PhysRevApplied.9.024023