Effect of adding aluminum ion on the structural, optical, electrical and magnetic properties of terbium doped yttrium iron garnet nanoparticles films prepared by sol-gel method

Tb0.8Y2.2AlyFe5−yO12 nanoparticle films with y = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 were prepared by a sol-gel method for potential use as a magnetic sensor and in magneto-optical applications. The films were deposited onto quartz substrate, followed by annealing at 900 °C in air for 2 h. X-ray diffractometry results confirmed the formation of a pure garnet structure. The lattice parameter decreased with increasing Al3+ content due to the substitution of Al3+ ions with the larger Fe3+ ions. The grain size of the films decreased up to y = 0.6. This variation is discussed based on the stress on the grain surface. The films observed to be transparent between 76 and 92% in the visible and infrared regions. The films demonstrated a strong absorption of 104 cm−1 caused by the charge transfer transition in the UV region. The absorption edge shifts to lower wavelengths at higher Al contents of 0.8 and 1 due to electronic transitions. The conductivity of films increased with increasing of Al content due to the increasing in free carrier concentration. The saturation magnetization at room temperature decreased with increasing Al3+ content, whereas the coercivity increased markedly at y = 0.6.