Exceptional elevated temperature behavior of nanocrystalline stoichiometric Y₂Fe₁₄B alloys with La or Ce substitutions

Considering that both La₂Fe₁₄B and Ce₂Fe₁₄B compounds exhibit similar weak temperature-dependent anisotropic fields (H_A) as Y₂Fe₁₄B, this work aims to clarify the elevated temperature behavior of melt-spun nanocrystalline La- or Ce-partially substituted stoichiometric Y₂Fe₁₄B alloys containing no critical rare earth elements. The results show that La-substituted (Y_1−xLa_x)₂Fe₁₄B alloys (x = 0–0.5) show exceptional elevated temperature behavior, manifested by the increased coercivity with increasing temperature. For the Ce-substituted (Y_1−xCe_x)₂Fe₁₄B alloys, only x = 0.1 and 0.2 alloys show the similar trend. Both the temperature coefficient of remanence α and coercivity β can be improved by La-substituted, indicating partial substitution La can effectively enhance the thermal stability of Y₂Fe₁₄B alloy. However, excess La or Ce substitution would reduce α and β value, resulting in the deterioration of thermal stability. Highest β values of 0.05 and − 0.08 have been obtained in (Y_0.9La_0.1)₂Fe₁₄B alloy at 300–400 K and (Y_0.8La_0.2)₂Fe₁₄B alloy at 300–500 K, respectively. In addition, Ce substitution can effectively enhance the coercivity of Y₂Fe₁₄B alloy at room temperature and La substitution does not show a beneficial effect on the room-temperature magnetic properties. This work is beneficial for developing high-performance/cost ratio permanent magnets based on abundant rare earth elements with superior thermal stability.