Effect of structural stacking on magnetocaloric and magnetodielectric properties of Ba1-xSrxCo0.9Mn0.1O3-δ (0 ≤ x ≤ 0.5)

Abstract

The effect of structural stacking sequence on magnetocaloric, critical behavior and dielectric properties in the nanocrystalline Ba1-xSrxCo0.9Mn0.1O3-δ (0 ≤ x ≤ 0.5) system has been investigated. The parent BaCo0.9Mn0.1O3-δ compound exhibit 12H-hexagonal phase. With increase in Sr-doping, structure changes to 2H-phase (x = 0.5) through mixed 12H+2H-phase (x = 0.1 and 0.3) for the samples annealed at 1100 °C. The magnetocaloric properties shows promising results in the presence of 12H-phase, whereas, inclusion of 2H-phase suppresses magnetocaloric properties. The maximum entropy change for a field change of 5 T is found to be 2.50, 1.73, 0.50 and 0.12 Jkg-1K−1 for x = 0.0, 0.1, 0.3 and 0.5 respectively. The field dependence of maximum entropy change under different composition ratio is studied using phenomenological scaling behavior of magnetic entropy change model. The nature of magnetic phase transition and critical behavior of the nanocrystalline system are studied using Landau theory and Arrot plots. The obtained critical exponents show deviation from mean-field model with increase in Sr-doping. In addition, influence of structural changes on temperature and field dependent dielectric properties is studied. The temperature variation of dielectric constant (ε′) shows subtle change in the vicinity of magnetic transition and the numerical value of ε’ suppresses with 2H-phase. The value of magnetocapacitance (MC %) is also get suppressed while going mixed 12H+2H- to 2H-phase. The origin of magneto-dielectric properties in the present nanocrystalline system demonstrates the strong correlation among structural, magnetic, electrical and dielectric properties.