Effect of Ba substitution on dielectric and magnetic properties in La2MnNiO6 double perovskite

This paper reports the synthesis of single-phase La_2-xBa_xMnNiO₆ (x = 0.0 and 0.5) double-perovskite using sol-gel auto-combustion route. ADXRD studies confirm the pure phase formation of the compound with the space group R $\bar{3}$ c and that no other structural transformation was observed even after Ba substitution. FESEM analysis show the formation of uniformly distributed ball-shaped nanoparticles and EDX spectra endorses the stoichiometric composition of the as prepared samples. The existence of mixed oxidation states of Ni and Mn ions is validated by XPS. The dielectric properties studied in the temperature range 100 K–320 K show the enhancement in the dielectric constant and the relaxor nature of the compound upon Ba substitution. The fitting of power law and Arrott's plot validates the presence of short-range ordering i.e. Griffith-like phase. The dielectric and magnetic properties are strongly linked and correlated based on enhanced antisite disorder (∼10 %). The ESR spectroscopy was used to calculate spin relaxation time and verify the existence of double exchange interaction in the compound.