Investigation of new magnetoelastic and magnetic transitions accompanied with magnetoelectric coupling in 0.1BiFeO3 - 0.9Sr(Fe0.5Nb0.5)O3 multiferroic.

Abstract

A new multiferroic solid solution 0.1BiFeO3-0.9Sr(Fe0.5Nb0.5)O3 has been developed and characterized for structure, phase transition, magnetoelectric and magnetoelastic coupling. Temperature dependent measurement of dc-magnetization M(T) on 0.1BiFeO3-0.9Sr(Fe0.5Nb0.5)O3 ceramic shows two magnetic transitions one around ⁓ 42K and the second at ⁓130K. The real part of dielectric permittivity exhibits step like change at the magnetic anomaly temperature (⁓130K) which indicates the presence of magnetoelectric coupling. The change in the value of dielectric permittivity on the application of magnetic field confirms the presence of magnetoelectric coupling in 0.1BiFeO3-0.9Sr(Fe0.5Nb0.5)O3 ceramic. The room temperature polarization (P)-electric field (E) hysteresis loop measurement shows week ferroelectric nature of sample while the magnetization (M) versus magnetic field (H) measurement suggest weakly ferromagnetic character. The ferroelectric nature of sample was further confirmed by calculating remanent polarization using PUND measurement. The Rietveld structural analysis of low temperature X-ray powder diffraction data does not reveal any crystallographic phase transition in terms of peak splitting or new reflections. However, temperature dependence of lattice parameters, tetragonality, unit cell volume, (Nb/Fe)O6 octahedral tilt angle (φ), Sr/Bi-O bond length and Fe/Nb-O-Fe/Nb bond angles reveal discontinuous changes at both the magnetic transitions observed in temperature dependence of magnetisation. This confirms that both the magnetic anomalies (around ⁓ 42K and ⁓ 130K) exhibit magnetoelastic coupling accompanied with isostructural transitions.