Magnetic Hardening of Ce$_{2}$Fe$_{\mathrm{14-x}}$Co$_{\mathrm{x}}$B

Permanent magnets based on R$_{2}$Fe$_{14}$B (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, both of which are currently subject to supply and cost instability. A possible alternative is R $=$ Ce, the most abundant rare earth, but Ce$_{2}$Fe$_{14}$B has several disadvantages, including a low Curie temperature (T$_{\mathrm{c}})$ that restricts the maximum operating point to well below that required for some applications. Given that substitution of Co for Fe is known to enhance T$_{\mathrm{c}}$ significantly in other R$_{2}$Fe$_{14}$B compounds, we systematically investigate magnetic hardening of Ce$_{2}$Fe$_{\mathrm{14-x}}$Co$_{\mathrm{x}}$B by melt spinning alloys having compositions guided by our previous work on the Ce-Fe-B system. We find the range of Co solubility in Ce$_{2}$Fe$_{14}$B to be markedly lower than for other R$_{2}$Fe$_{14}$B materials, a consequence of the fact that Ce$_{2}$Co$_{14}$B apparently does not form.