An evidence of local structural disorder across spin-reorientation transition in DyFeO₃: an extended x-ray absorption fine structure (EXAFS) study

Abstract

The present work is aimed at exploring the local atomic structure modifications related to the spin reorientation transition (SRT) in DyFeO 3 orthoferrite exploiting x-ray absorption fine structure (XAFS) spectroscopy. For this purpose we studied by XAFS the evolution of the local atomic structure around Fe and Dy as function of temperature (10-300 K) in a DyFeO 3 sample having the SRT around 50-100 K. For sake of comparison we studied a YFeO 3 sample having no SRT. The analysis of the extended region has revealed an anomalous trend of Fe-O nearest neighbour distribution in DFO revealing (i) a weak but significant compression with increasing temperature above the SRT and (ii) a peculiar behavior of mean square relative displacement (MSRD) [σ 2 ] of Fe-O bonds showing an additional static contribution in the low temperature region, below the SRT. These effects are absent in the YFO sample supporting these anomalies related to the SRT. Interestingly the analysis of Dy L 3-edge data also reveal anomalies in the Dy-O neighbour distribution associated to the SRT, pointing out a role of magnetic Re ions across T SRT,Fe. These results point out micro-structural modification at both Fe and Dy sites associated to the magnetic transitions in DFO, it can be stated in general terms that such local distortions across Fe 3+ and magnetic Re 3+ may be present in other orthoferrites exhibiting multiferroic nature.

EXAFS evidence for the spin–phonon coupling in the monoclinic PrNiO3 nickelate perovskite

“…DyFeO 3 orthoferrite has the same orthorhombic crystal structure (Pbnm) of PrNiO 3 under room conditions. 31 This orthoferrite is a magnetic system with a spin reorientation transition (SRT) in the range of 50-100 K. Panchwanee et al reported a slight compression of the bond Fe-O above SRT and an anomaly in s G 2 similar to that seen for the bond Ni-O in PrNiO 3 at magnetic ordering temperature T N E 130 K, the anomaly being absent in the paramagnetic YFeO 3 orthoferrite.…”

“…DyFeO3 orthoferrite has the same orthorhombic crystal structure (𝑃𝑏𝑛𝑚) of PrNiO3 at room conditions. 31 This orthoferrite is a magnetic system with a spin reorientation transition (SRT) in the range 50-100 K. Panchwanee et. al.…”

EXAFS spectroscopy: a powerful tool for the study of local vibrational dynamics

“…The first nearest-neighbor shells around Fe and Ni both show a suppression of the bond thermal expansion, although the anharmonicity, with important quantum effects at low temperature, is clearly evident. Panchwanee et al [128] explored the local modifications associated with the spin-reorientation transition in DyFeO 3 orthoferrite. They observed a shrinkage of the Fe-O bond length above the spin-reorientation transition and the activation of static distortion of Fe-O bonds below.…”