Impact of hydrogenation on the structural, dielectric and magnetic properties of La0.5Ca0.5MnO3

Impact of hydrogenation on the structural, dielectric and magnetic properties of half-doped La 0.5 Ca 0.5 MnO 3 manganate have been investigated. Polycrystalline sample of La 0.5 Ca 0.5 MnO 3 was prepared through solid state reaction at ~ 1300 °C. Subsequently, the prepared sample was annealed at 600 °C for 6 h in a continuous flow of hydrogen gas in a tubular reduction furnace. Single-phase orthorhombic structure of the hydrogenated La 0.5 Ca 0.5 MnO 3 in the space group Pnma was confirmed by Rietveld refinement of PXRD and FTIR analysis. SEM micrographs revealed well resolved grains of ~ 2 μm in a good crystalline sample. Hydrogenated La 0.5 Ca 0.5 MnO 3 showed a sharp optical absorption peak in the UV range with a bandgap energy of 4.96 eV. Hydrogenation of La 0.5 Ca 0.5 MnO 3 leads to significant reduction in the magnitude of dielectric constant and tangent loss at room temperature. Paramagnetic character of La 0.5 Ca 0.5 MnO 3 at 300 K is retained upon the hydrogenation but the low temperature magnetic properties get modified dramatically. Temperature and field dependent magnetization measurements showed that hydrogenated La 0.5 Ca 0.5 MnO 3 undergoes paramagnetic to antiferromagnetic transition at T N = ~ 110 K and in a disordered magnetic phase below 50 K. Systematic enhancements in the magnitude of saturation magnetization ( M s ), coercivity ( H c ), remanence ( M r ) and squareness ratio at 50 K and 20 K indicate for the coexistence of antiferromagnetic and weak ferromagnetic order due to competitive magnetic exchange interactions between Mn 3+ and Mn 4+ ions. This study shows that hydrogenation plays key role in the modification of dielectric and magnetic properties of La 0.5 Ca 0.5 MnO 3 .