Etude magnetique des materiaux de type Ln2M12P7 (Ln = Ce, Sm, Gd et Er; M = Co et Fe)

A magnetic study has been undertaken on the substances of formula Ln2M12X7. The magnetic susceptibility and the magnetization have been measured as a function of temperature for a constant field. The magnetic susceptibility measurements have been performed from ambient temperature up to 1000 K. The effective paramagnetic moments were deduced from 1/(xi) = f(T) curves, assuming a zero moment on the transition metal atoms. It is shown that these values are in good agreement with the theoretical values calculated for the free ions Ln3+. The saturation moment and the paramagnetic Curie temperature values show an antiferromagnetic behavior for Ce2Co12P7 at low temperature. The magnetic moment of Sm2Co12P7 measured at 4.2 and 78 K under a 2.66 T magnetic field shows a complex magnetic structure at low temperature. Our work on these materials show that the magnetic properties of Ln2M12X7 could be interpreted from previous studies on the phases rare earth - transition metal Ln-M.