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 La0.5Ca0.5MnO3 manganate have been investigated. Polycrystalline sample of La0.5Ca0.5MnO3 was prepared through solid state reaction at similar to 1300 degrees C. Subsequently, the prepared sample was annealed at 600 degrees C for 6 h in a continuous flow of hydrogen gas in a tubular reduction furnace. Single-phase orthorhombic structure of the hydrogenated La0.5Ca0.5MnO3 in the space group Pnma was confirmed by Rietveld refinement of PXRD and FTIR analysis. SEM micrographs revealed well resolved grains of similar to 2 mu m in a good crystalline sample. Hydrogenated La0.5Ca0.5MnO3 showed a sharp optical absorption peak in the UV range with a bandgap energy of 4.96 eV. Hydrogenation of La0.5Ca0.5MnO3 leads to significant reduction in the magnitude of dielectric constant and tangent loss at room temperature. Paramagnetic character of La0.5Ca0.5MnO3 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 La0.5Ca0.5MnO3 undergoes paramagnetic to antiferromagnetic transition at T-N= similar to 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 Mn3+ and Mn4+ ions. This study shows that hydrogenation plays key role in the modification of dielectric and magnetic properties of La0.5Ca0.5MnO3.