Magnetic property study of Gd doped TiO₂ nanoparticles

Highlights: • Gd doping has modest influence on the internal structure of TiO₂. • The doped samples exhibit paramagnetism at room temperature. • Isolated magnetic spin of Gd³⁺ ions contribute towards paramagnetism. • Superexchange interaction of Gd³⁺ ions via O²⁻ ions induces antiferromagnetism. - Abstract: In this work we have studied the magnetic properties of sol–gel synthesized Gd doped TiO₂ nanoparticles. The Gd concentration varying from 0.03 to 0.07 mol. Structural, morphological and compositional analyses have been monitored with X-ray diffraction, transmission electron microscope (TEM), Raman spectroscopy and energy dispersive X-ray (EDX) spectroscopy. XPS spectra establish that Gd ions are in the +3 oxidation state. Photoluminescence intensity enhances at 0.03 and 0.05 mol and then quenches at 0.07. This is likely due to the formation of emission quenching centers. All the samples exhibit paramagnetism at room temperature as well as at 10 K. It is observed that due to the shielding of 4f shell of Gd³⁺ ions by 6s5d shell the direct exchange interaction of these Gd³⁺ ions with other Gd³⁺ ions is weak. These non-interacting and localized magnetic spins of Gd³⁺ induce only paramagnetism. The high magnetization exhibited by the samples at 10 K is due to minimization of the thermal randomization of the magnetic spins. Antiferromagnetic interaction persists at 0.03 mol and it gets stronger at 0.07 mol. Antiferromagnetism appears due to strong superexchange interaction of Gd³⁺ ions via O²⁻ ions