Al,Ga substitution in RE2Fe17 (RE=Ce,Pr,Nd): Magnetic behavior of RE2Fe15(Al,Ga)2 alloys

Abstract

Alloys with the composition RE₂Fe₁₇ and RE₂Fe₁₅X₂ (X=Al,Ga) have been synthesized by the arc‐melting technique followed by an 125‐h anneal at 900–1000 °C in evacuated silica capsules. The new compound Nd₂Fe₁₅Ga₂ is unstable below 800 °C, and is only obtained by quenching from above 900 °C. From x‐ray powder diffraction analysis all alloys except Pr₂ Fe₁₅ Ga₂ were found to crystallize with the hexagonal Th₂ Zn₁₇ type; indications for a preferential occupation of the (6c) sites by the X atoms are small. Substitution of Al, Ga atoms generally leads to a large increase of the Curie temperature and of the magnetocrystalline anisotropy, thereby enhancing the remanence as well as the coercivity. These effects are a consequence of the strongly distance‐dependent exchange interactions of the Fe‐Fe and Fe‐RE coupling mechanisms. As for binary Pr₂ Fe₁₇ , the easy axis of magnetization for Pr₂ Fe₁₅ Al₂ was found to be in the basal plane.