Investigation of multi-mode spin-phonon coupling and local B-site disorder in Pr2CoFeO6 by Raman spectroscopy and correlation with its electronic structure by XPS and XAS studies

Arkadeb Pal; Surajit Ghosh; Amish G Joshi; Shiv Kumar; Swapnil Patil; Prince K Gupta; Prajyoti Singh; V K Gangwar; P Prakash; Ranjan K Singh; Eike F Schwier; M Sawada; K Shimada; A K Ghosh; Amitabh Das; Sandip Chatterjee

doi:10.1088/1361-648X/ab144f

Investigation of multi-mode spin-phonon coupling and local B-site disorder in Pr₂CoFeO₆ by Raman spectroscopy and correlation with its electronic structure by XPS and XAS studies

J Phys Condens Matter. 2019 Jul 10;31(27):275802. doi: 10.1088/1361-648X/ab144f. Epub 2019 Mar 28.

Authors

Arkadeb Pal¹, Surajit Ghosh, Amish G Joshi, Shiv Kumar, Swapnil Patil, Prince K Gupta, Prajyoti Singh, V K Gangwar, P Prakash, Ranjan K Singh, Eike F Schwier, M Sawada, K Shimada, A K Ghosh, Amitabh Das, Sandip Chatterjee

Affiliation

¹ Department of Physics, Indian Institute of Technology (BHU), Varanasi 221005, India.

PMID: 30921773
DOI: 10.1088/1361-648X/ab144f

Abstract

Electronic structure of Pr₂CoFeO₆ (at 300 K) was investigated by x-ray photoemission spectroscopy (XPS) and x-ray absorption spectroscopy techniques. All three cations, i.e. Pr, Co and Fe were found to be trivalent in nature. XPS valance band analysis suggested the system to be insulating in nature. The analysis suggested that Co³⁺ ions exist in low spin state in the system. Moreover, Raman spectroscopy study indicated the random distribution of the B-site ions (Co/Fe) triggered by same charge states. In temperature-dependent Raman study, the relative heights of the two observed phonon modes exhibited anomalous behaviour near magnetic transition temperature T _N ~ 270 K, thus indicating towards interplay between spin and phonon degrees of freedom in the system. Furthermore, clear anomalous softening was observed below T _N which confirmed the existence of strong spin-phonon coupling occurring for at least two phonon modes of the system. The line width analysis of the phonon modes essentially ruled out the role of magnetostriction effect in the observed phonon anomaly. The investigation of the lattice parameter variation across T _N (obtained from the temperature-dependent neutron diffraction measurements) further confirmed the existence of the spin-phonon coupling.