Structural, ac conductivity scaling and magnetodielectric behaviour of a partially disordered insulating ferromagnetic double perovskite Eu2NiMnO6

Double perovskites are interesting materials with immense prospects for technological implications. A ferromagnetic double perovskite Eu2NiMnO6 with a rare-earth ion was synthesised by a solid state ceramic route. Room temperature x-ray powder diffraction study of the compound revealed a monoclinic P2(1)/n structure associated with anti-phase tilting of the distorted MnO6 and NiO6 octahedra, which influenced its magnetic, electrical, transport and magnetodielectric properties. Analysis of the structural and magnetic data indicated about similar to 10% disordered arrangements of the Ni/Mn cations and an onset of ferromagnetic-type ordering around temperature T-c similar to 150 K. True long-range ferromagnetic ordering was not obvious because of the observed large difference of field-cooled and zero-field cooled magnetisation below the ferromagnetic ordering around T-c. Eu2NiMnO6 showed quite a high room temperature dielectric permittivity (similar to 10(3)) with moderately low loss (loss tangent similar to 1.09 at a typical frequency of 10 kHz), and also a considerably low field magnetodielectric response (similar to 10% at 11.6 kHz and at low external field of similar to 1 T) was observed. Typical Debye-type dielectric relaxation behaviour was revealed from the analysis of the dielectric constant data and interesting scaling behaviour was exhibited by both ac conductivity and electric modulus. Such a high dielectric low loss ferromagnetic double perovskite might be considered as a potential candidate for applications in devices.