Evolution of structure, vacancy characteristics, dielectric and magnetic properties of GdMnO3 ceramics induced by Li plus ion substitution

This work studies the influences of Li+ ion substitution for Gd on the structure, vacancy characteristics, magnetic and dielectric properties in GdMnO3 ceramics prepared by solid-state method. XRD measurements indicate that all of the Gd1-xLixMnO3 ceramics show single phase structure, the introduction of Li+ ions induces structure distortion. XPS results show that Li+ ions substitution introduces more Mn4+ in GdMnO3, while has no significant effect on oxygen vacancy concentration. Positron annihilation experimental results indicate that the vacancies concentration increases first and then reduces with increasing Li+ ions content. The evolution of the temperatureand magnetic field-dependent magnetization curves presents that the magnetic transition temperature and magnetization of Gd1-xLixMnO3 could obviously be improved by Li+ ion substitution. Dielectric measurements reveal that the Li+-substituted samples exhibit giant dielectric constant characteristics over a broad frequency range. It is found that the enhanced magnetization of Gd1-xLixMnO3 has a close relationship with vacancies concentration, and the giant dielectric constant behaviors of Gd1-xLixMnO3 ceramics can be associated with the mixed-valent structure of Mn3+/Mn4+ and < Mn-O-Mn > bond angle.