Heavy-rare-earth-induced structural and magnetic properties in (Sr2-xLnx)FeMoO6 (Ln = Sr, Gd, Tb, Dy , Y and Ho) double perovskite

Heavy-rare-earth-doped (HR-doped) (Sr2-xLnx)FeMoO6 (x = 0, 0.1 and 0.15, Ln = Sr, Gd, Tb, Dy, Y and Ho) have been synthesized by solid-state reaction. Crystal structure, magnetic and transport properties of the compound are investigated systematically. Structural refinement shows that although all the compounds belong to the same space group, I4/m, prominent structural distortion is introduced: all the compounds seem to be divided into two groups: for (Sr2-xGdx)FeMoO6 and (Sr2-xTbx)FeMoO6 compounds, FeO6 octahedra becomes expansive and MoO6 octahedra becomes contractive, while FeO6 octahedra is compressed and MoO6 octahedra is stretched for the other compounds. Owing to the competing interaction between structural distortion and electron doping, TC of (Sr2-xGdx)FeMoO6 and (Sr2-xTbx)FeMoO6 is increased, resistivity is decreased and metallic behavior is enhanced, while the reverse occurs to the other compounds. Saturation magnetization of (Sr2-xLnx)FeMoO6 suggests that the long-range-ordered-moments of Gd3+, Tb3+, Dy3+ and Ho3+ maybe parallel with that of Fe3+ spin at low temperature, which is the same as La-, Ce-, Pr-, Nd- and Sm-doped case. Above results reveal that rare earth elements (La-Ho, except for Eu) exhibit the same coupling effect with Sr2FeMoO6, despite of their different magnetic nature. Our investigation offer comprehensive knowledge on the structural and magnetic properties of rare-earth-doped Sr2FeMoO6.