(La_2/5Ba_2/5Ca_1/5)(Mn_(2/5)−x Ni_xTi_3/5)O₃: Rietveld studies, dielectric and magnetic properties of new perovskite-related oxides

Abstract

Oxides of the type (La_2/5Ba_2/5Ca_1/5)(Mn_(2/5)−x Ni_xTi_3/5)O₃ (0 ≤ x ≤ 0.4) have been synthesized by the ceramic route. All the above oxides have been found to crystallize in the cubic perovskite structure. Rietveld refinement of the Ni-based oxide, (La_2/5Ba_2/5Ca_1/5)(Ni_2/5Ti_3/5)O₃ gave rise to a composition (La_0·44Ba_0·38Ca_0·18) Ni_2/5Ti_3/5 and the refined lattice parameter obtained was 3·9411(2) Å (space group Pm3̅m;R(F²) = 0·026,R _p = 0·074,wR _p = 0·087). A shift from antiferromagnetic to paramagnetic behaviour is observed with increase in nickel concentration, the Mn-rich phases showing antiferromagnetism around 5 K. There is a systematic decrease in the dielectric constant, ε and loss tangent with increase in Ni concentration (from ε= 592 for x = 0 to ε = 78 for x = 0·4).