Tuning of band gap, spin reorientation transition along with unusual coercivity in CeCr1-xFexO3 (0.2 ≤ x ≤0.5) perovskite nanoparticles

Abstract

Here, we have investigated structural, optical and magnetic properties of CeCr_1-xFe_xO₃ (0.2 ≤ x ≤ 0.5) nanoparticles synthesized through combustion technique. Structural parameters determined from refinement shows that with increase in x from 0.2 to 0.5, both lattice parameters and volume increase. In addition to Fe³⁺ and Cr³⁺, we observe Fe²⁺ and Cr⁶⁺ from XPS (X-ray photoelectron spectroscopy) spectra and the concentration of Fe²⁺ increases more than that of Cr⁶⁺, showing an increase in lattice parameters. Band gap varies from 2.56 to 1.15 eV with increasing x from 0.2 to 0.5 which is ascribed to an increase in the ratio of Fe²⁺ to Fe³⁺ along with the increase in particle size. Surprisingly, the spin reorientation temperature, T_SR increases from 62 K to 138 K with increase in x from 0.2 to 0.5 respectively. The increase in T_SR is attributed to the enhanced Ce³⁺-Fe³⁺ interaction at the expense of Ce³⁺-Cr³⁺ interaction. Besides, an anomalous increase in H_C has been observed at the vicinity of T_SR irrespective of composition. With increasing x, the increase in Fe²⁺ concentration introduces double exchange interaction (Cr³⁺/Fe³⁺-Fe²⁺) and results in transition from complex antiferromagnetic (AFM) behavior to ferromagnetic (FM) one when x = 0.5. The enhancement in T_SR along with tunable coercivity make these materials a potential candidate for spintronics, and magnetic switching devices.