Neutron diffraction studies of Ho2Fe9Ga8-xAlx (x= 2, 4) at 50 K and 300 K

The crystallographic and magnetic structures of (x = 2, 4) were studied by powder neutron diffraction at 50 K and 300 K. The atom fractional occupancies of gallium and aluminium and the magnetic moments of Ho and Fe atoms were obtained by a Rietveld analysis program. The gallium atoms occupy preferentially 18f sites, but aluminium atoms prefer to occupy 6c sites. The magnetic moments of the phase with the x = 2, 4 at 50 K and x = 2 at 300 K show uniaxial anisotropy. A qualitative explanation for this result is given.