Neutron structure analysis and magnetic properties of Ho2Fe17-xGax (x = 5, 8)

The crystallographic and magnetic structures of Ho2Fe17-xGax(x = 5,8) compounds at room temperature were refined by Rietveld analysis of the neutron powder diffraction data. The analysis indicates that Ho2Fe17-xGax(x = 5, 8) compounds have Th2Zn17 type structure (SG R(3) over barm$). For x = 5 Ga atoms partially occupy 18h and 18f sites with the occupancies of 0.40 and 0.43, and for x = 8 they occupy 18h, 18f and 6c sites with the occupancies of 0.20, 0.80 and 1.0 respectively. The magneto-anisotropy changes from easy planar to easy-axial when the Ga content x increases from 5 to 8. The magnetic measurements show that the magnetic ordering temperature T-c increases abnormally with Ga content x increasing from 6.5 to 8. This paper gives a reasonable explanation for this phenomenon.