Abstract:
In this investigation, structural, magnetic, and optical properties of polycrystalline double perovskites Dy2FeCrO6 (DFCO) and Dy2NiCrO6 (DNCO) have been investigated. Both materials have been synthesized by sol‒gel reaction technique. Rietveld refinement of the room temperature powder X‒ray diffraction pattern confirmed the formation of single phase of the materials. It is found that all the materials crystallized in monoclinic (space group P21/n) phase. Crystallite size of DFCO and DNCO are found to be 42 nm and 40 nm respectively calculated by Scherrer equation. Calculated bond angles and bond lengths of both materials indicate the presence of octahedral tilting and Jahn-Teller distortion. Quantitative estimation of valance states of atoms of DFCO and DNCO have been carried out by bond valance sum (BVS) calculations from bond lengths found by Rietveld refinement. From BVS analysis, it is found that DFCO have Dy23+Fe3+Cr3+O62- configuration and DNCO have
Dy23+Ni2+Cr4+O62- valance configuration. Surface morphology of both materials is
found to be inhomogeneous, ensured by Field Emission Scanning Electron Microscope (FESEM) images. Presence of all necessary elements to form DFCO and DNCO are confirmed by Energy-dispersive X-ray spectroscopy (EDX). Field depended magnetization measurement of DFCO show that DFCO is ferrimagnetic at room temperature with clear magnetic hysteresis loop. At room temperature DNCO demonstrates paramagnetic behavior. Antiferromagnetic nature of DNCO has been observed at low temperature M-H measurement. Both materials demonstrate considerably high absorbance in the visible range with low band gap, 1.91 eV of DFCO and 2.2 eV of DNCO. To get deep insight into the magnetic and optical properties first principles calculations based on density functional theory (DFT) have been carried out. Outcomes of DFT confirm ferrimagnetic ground state of DFCO and antiferromagnetic ground state of DNCO in terms of minimum energy state. From band structure analysis DFCO is found to be an indirect band gap semiconductor and DNCO is a direct band gap semiconductor. The experimentally observed band gap is in excellent agreement with the calculated band gap using first-principles calculations. Due to the presence of band gap in the visible range and room temperature ferrimagnetic nature of DFCO, it could be a promising candidate for photocatalytic and spintronics applications.
