Local valence and physical properties of double perovskite Nd2NiMnO6

A polycrystalline double perovskite Nd2NiMnO6 (NNM) has been synthesized through the solid-state reaction method. Powder x-ray diffraction data can be indexed by the space group P21/n. Double magnetization transition temperatures at 105.12K and 193.04K are observed from temperature-dependent magnetization curve and can be ascribed to Ni3+-O-Mn3+ and Ni2+-O-Mn4+ superexchange interactions, respectively. The effective magnetic moment, Curie constant C and paramagnetic Curie-Weiss temperature theta are calculated to be 6.023 mu B/f.u., 4.529(4) emu K mol(-1) Oe(-1) and 191.1(9) K, respectively. Mixed valence of Mn ion is further evidenced by x-ray photoelectron spectra and the mole ratio of Mn3+/Mn4+ is determined to be 19.53 : 81.47. The dielectric relaxor behaviour is found in NNM and follows the Vogel-Fulcher relationship with E-a = 0.0264 eV, T-f = 283.2K and f(0) = 4.66 x 10(8) Hz. The delocalized carriers in the semiconducting sample may explain the origin of dielectric relaxation.