Probing the spin-phonon coupling through Raman spectroscopy in Pb(Fe1/2Nb1/2)O3 – Pb(Co1/3Nb2/3)O3 ceramics

Abstract

We report on the spin-phonon coupling in (1-x)Pb(Fe1/2Nb1/2)O3 – (x)Pb(Co1/3Nb2/3)O3 (PFCN, x = 0.1–0.5) ceramics by noticing changes in the phonon modes around the magnetic phase transition (TN) in the temperature-dependent Raman spectroscopy. A huge bifurcation was found between MZFC and MFC curves, revealing the existence of strong magnetic anisotropy in all the ceramics. Variations in TN are due to the coexistence of antiferromagnetic and ferromagnetic interactions through Fe–O–Fe, Co–O–Co, Fe–O–Co canted magnetic moments. The Tg is due to the superexchange interaction among Fe/Co–O–Nb–O–Co/Fe paths formed by the local short-range chemical ordering of Fe, Co, and Nb ions. The Raman spectra, recorded over a wide range of temperatures, reveal some anomalies in B–O–B bending and O–B–O stretching modes in the vicinity of TN, corresponding to the spin-phonon coupling in all the ceramics. This evidences the existence of magnetoelectric coupling in all the PFCN ceramics. Room temperature Mössbauer spectra of x = 0.1, 0.3 and 0.5 revealed the paramagnetic nature. Electron paramagnetic resonance (EPR) spectra showed the existence of antiferromagnetic and ferromagnetic orderings in all the ceramics.