Crystal structure and magnetic properties of Ce2Fe14−xCoxB alloys

Highlights: •Annealed melt-spun Ce3Fe14−xCoxB or Ce2.55Fe14−xCoxB1.27 ribbons maintain the Ce2Fe14B crystal structure only for x ⩽ 5. •In contrast to many other R2Fe14B materials, we find no evidence for the formation of Ce2Co14B. •The Curie temperature increases rapidly with increasing cobalt content x, reaching ∼660 K for x = 5. •Ce3Fe12Co2B offers significant improvement in Tc, Br, and (BH)max relative to its Co-free analog with only modest Hci loss. -- Abstract: Permanent magnet materials based on the R2Fe14B phase (R = rare earth element) are essential to a wide variety of applications, among them automotive traction motors. Current state-of-the-art materials rely on R = Nd and Dy, for both of which there are supply uncertainties and rapidly rising costs. A possible alternative is R = Ce, the most abundant rare earth, but Ce2Fe14B has several disadvantages, including a low Curie temperature (Tc) that limits its maximum operating point to well below that required for some automotive uses. Here we systematically investigate the Ce2Fe14−xCoxB system by exploring Co substitution for Fe in melt-spun ribbons as a means of increasing Tc. In addition to Tc we report the solubility of Co in Ce2Fe14B and its effect on the crystal structure and hard magnetic properties