Magnetic properties of RM₆Al₆ (R = light rare earth, M = Cu, Mn, Fe)†

The systems RM₆Al₆ were studied by X-ray, magnetization and Mossbauer spectroscopy (⁵⁷Fe and ¹⁵¹Eu) measurements. The RCu₆Al₆ which crystallize in the f.c.c. NaZn₁₃ structure order ferromagnetically at low temperatures (T_c = 16K for R = Eu). The RMn₆Al₆ systems which crystallize in the rhombohedral Th₂Zn₁₇ structure order antiferromagnetically (T_n = 25K for R = Ndand Eu). LaFe₆Al₆ has the NaZn₁₃ structure and orders antiferromagnetically at a relatively low temperature, 38K. The correlation of crystal structure and magnetic properties of these systems and those of RM₆Al₆ (R = heavy rare earth, tetragonal ThMn₁₂ structure) are discussed.