An investigation of structural, magnetic and dielectric properties of R{sub 2}NiMnO{sub 6} (R = rare earth, Y)

We have investigated the structure, magnetic and dielectric properties of the double perovskite oxides, R{sub 2}NiMnO{sub 6} (R = Pr, Nd, Sm, Gd, Tb, Dy, Ho and Y). We could refine powder X-ray diffraction patterns of all the phases on the basis of monoclinic (P2{sub 1}/n) double perovskite structure where Ni and Mn atoms are ordered at 2c and 2d sites, respectively. All the phases are ferromagnetic insulators exhibiting relatively low dielectric loss and dielectric constants in the range 15-25. The ferromagnetic ordering temperature of the R{sub 2}NiMnO{sub 6} series seems to correlate better with the radius of R{sup 3+} atoms than with the average Ni-O-Mn angle ({phi}) in the double perovskite structure. These results are consistent with all samples having Mn{sup 4+} and Ni{sup 2+} with minimal antisite disorder.