Temperature and field induced magnetic and dielectric properties of monovalent (Li⁺¹) doped multiferroic GdMnO₃: grain and grain boundary effect on relaxation

This study explores the impact of lithium (Li) doping on the structural, electronic, magnetic, dielectric, and impedance properties of GdMnO₃. Gd_1−xLi_xMnO₃ (x = 0.05, 0.10 and 0.15) samples were synthesized using conventional solid state reaction method. X-ray diffraction confirms that all compounds maintain an orthorhombic structure with Pbnm space groups, with a decrease in unit cell volume as Li concentration increases, attributed to the smaller ionic radius of Li⁺ compared to Gd³⁺. X-ray photoelectron spectroscopy reveals the presence of Mn³⁺ and Mn⁴⁺ states, with Mn⁴⁺ concentrations of 29.78% in G85, 22.10% in G90, and 15.39% in G95. Magnetic measurements indicate Neel temperatures (T_N) of 41.02 K for G90 and 40.52 K for G95, suggesting a shift in T_N towards higher values with increased Li doping, suggesting enhanced magnetic interactions. Dielectric studies demonstrate temperature and frequency-dependent behaviours, with activation energies decreasing from 0.209 eV in G95 to 0.166 eV in G85 for grain relaxation and from 0.230 eV in G95 to 0.210 eV in G85 for grain boundary relaxation suggesting improved charge carrier mobility. Impedance spectroscopy highlights the contributions from grain and grain boundary effects, showing a reduction in impedance with increased Li doping, indicative of enhanced charge carrier mobility. These quantitative findings indicate that Li-doped GMO materials are promising for applications in advanced magnetic and dielectric devices, where specific doping levels can optimize performance.