Neutron diffraction study of Er2Fe15A12 and Er2Fe12A15

The crystallographic and magnetic structures of Er2Fe15Al2 and Er2Fe12Al5 have been refined in Gaussian peak-shape by Rietveld analysis of Neutron diffraction data. The refined results indicated that Er2Fe15Al2 compound has Th2Ni17-typc hexagonal structure (space group: P63/mmc) and Er2Fe12Al5 has Th2Zn17-type rhombohedral structure (space group:R 3m). The Al atoms prefer 12j and 12k sites with ccupancies 0.21 and 0.13, respectively, in Er2Fe15Al2 and prefer 18f, 18h and 6c sites with occupancies 0.35, 0.36 and 0.37, respectively, in Er2Fe12Al5. The magnetic moments of all Fe atoms display ferromagnetically arrangement and the moments of Er atoms couple ferrimagnetically to the moments of the Fe atoms. The moments lie in the plane perpendicular to the six-fold axis and exhibit planar magnetic anisotropy in both samples. The values of Tc were given and the neutron refined results coincide with that of the magnetic measurements. The relation between magnetic properties and structures was discussed.