Effect of substitution of Ga on the structure and magnetic properties of Dy₂Co_17−xGa_x (0≤x≤7) compounds

Abstract

A series of Dy2Co17−xGax polycrystalline samples with x from 0 to 7 were prepared by arc melting. X-ray powder diffraction analysis indicated that these compounds have the hexagonal Th2Ni17 structure for x≤3 and the rhombohedral Th2Zn17 structure for 3.5≤x≤7. The lattice parameters a and c increase linearly with the gallium content until x=5.3. With further increasing the gallium content x up to 7, the lattice parameter c slightly decreases, whereas the lattice parameter a increases more quickly than that for 0≤x≤5.3. The unit-cell volume shows an approximately linear increase of 6.1 Å3/Ga for 0≤x≤3.0 and 10.1 Å3/Ga for 3.5≤x≤7.0, respectively. Rietveld refinement of the Dy2Co11.7Ga5.3 compound reveals that the Ga atoms occupy all the 6c, 9d, 18f, and 18h sites and preferentially occupy the 6c site. The Curie temperature and the saturation magnetization of the rhombohedral Dy2Co17−xGax compounds decrease almost linearly with increasing Ga content.

Structure and magnetic properties of TbFe6Ga6+ compounds

“…Experimental results show that the magnetization of the TbFe 6Àx Ga 6+x decreases strongly with temperature decreases below the magnetic ordering temperature. The similar phenomena are also found in other R-T gallides, such as Dy 2 Co 17Àx Ga x [12], Tb 2 Co 17Àx Ga x [13], and LaFe 13Àx Ga x C [3]. In these compounds, the R-sublattice magnetization is antiparallel to the Fe-sublattice magnetization.…”

“…The coercivities, 0.12 T were observed in the sample TbFe 6Àx Ga 6+x with x ¼ 0, 0.5 in the orthorhombic ScFe 6 Ga 6 -type structure, but very small for the sample TbFe 6Àx Ga 6+x with x ¼ 1.0 and 1.45 in the tetragonal ThMn 12 -type structure. Larger coercivity in the sample TbFe 6Àx Ga 6+x with the orthorhombic ScFe 6 Ga 6 -type structure may be due to its nearly uniaxial (11 0) anisotropy from its ordering structure, as comparing to the planer anisotropy of TbFe 6Àx Ga 6+x with the tetragonal ThMn 12 …”