Thermal expansion anomalies of R(Fe, M)12 (R=Y, Nd; M=Mo and Si)

Structural and thermal-expansion anomaly studies on R(Fe,M)12 (R=Nd and and Y, M=Mo and Si) compounds were performed by x-ray diffraction. Mo atoms occupy the 8i site. While Si atoms occupy the 8f and 8j sites but not the 8i site. Thermal-expansion anomaly shows only in ab plane in the Mo compounds, while becomes very weak and along with only the c axis in the Si compounds. The anomaly was attributed to the contribution of the interactions of short Fe–Fe distances similar to the previous explanation on other R–Fe intermetallics and that of other strongly positive interactions such as 8j-8j.