Effects of iron substitution and anti-site disorder on crystal structures, vibrational, optical and magnetic properties of double perovskites Sr₂(Fe_1−xNi_x)TeO₆

Abstract

We report a new series of DP Sr2(Fe1−xNix)TeO6, which have different transition metal Fe and Ni on B sites, providing an opportunity to investigate their effect on crystal structure, vibrational, optical and magnetic properties.

Crystallography at non-ambient conditions and physical properties of the synthesized double perovskites, Sr2(Co1−xFex)TeO6

“…Otherwise, the model is not able to correctly reproduce the experimental intensity of many peaks in the diffractograms. 67 The obtained cationic distributions are in good agreement with the calculated bond valence sum (BVS) of Co/Fe and Te, which confirms as well that the system could keep the formal valences of these elements. It is worth noting that the thermal displacement parameters during the refinement were fixed.…”

“…As a result, a partial disorder occurs when the atoms of Fe set together with Te (a cationic distribution of Fe from the 2 d site to the 2 a site occurs), with the appearance of vacancies in the 2 d site to make charge compensation for the Fe 3+ cations in the system. This strategy gave similar results to the one reported by Ortega-San Martin et al and Zaraq et al 41,67 Concerning the other compositions with Fe-doping for x = 0.25 and 0.50, the same method of refinement was used with keeping the Co atoms only on the 2 d site. As the formation of the vacancies is related to the location of Fe with Te, it is normal that the number of vacancies is increasing as the Fe quantity increases.…”

“…To determine the optical band gap, a combination of two methods was used, Tauc 62 and DASF. 67 The idea is to fit the DR-UV-vis data in order to extract the band gap energies and the obtained absolute value is estimated to be the band-gap energy. Moreover, the difference between the values of the band gap E i and E d can help determine the type of transition.…”