Is it possible the substitution of Cr cations from spinel-type oxides with bulky rare-earth cations by sol–gel auto-combustion method?

Rare-earth La³⁺ cations, with large ionic radii, substituted ZnCr_2−xLa_xO₄ nanoparticles with x ranging from 0.0 to 0.50 were synthesized by sol–gel auto-combustion technique. Effect of La substitution on structural and magnetic properties of ZnCr₂O₄ spinel oxide is reported. The phase composition of the obtained powders was investigated by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. Magnetic measurements were made using a SQUID magnetometer. FT-IR and X-ray diffraction revealed the transition of spinel structure to perovskite structure because of the exchange of Zn²⁺ and La³⁺ cations among constituent A-sites. The particle size were estimated from the SEM micrographs and were found to increase with the La ions substitution from 48 to 80 nm. It was revealed from the magnetic measurements that magnetization follow a decreasing trend with substitution of Cr³⁺ ions by paramagnetic La³⁺ ions. Also, the magnetization showed a drastic decrease with increase of temperature from 2 K to 300 K because of enhanced domain pinning effect, due to the La³⁺ substitution. - Highlights: • Synthesis of La³⁺ substituted zinc chromite materials is reported. • Is it possible the substitution of Cr in spinel-type oxides with bulky RE cations? • A shift from cubic to orthorhombic structure starting with x = 0.25 was observed. • La ions occupy only constituent A-sites through complete substitution of Zn ions. • Drastic decrease of magnetization with temperature due to structural transition.