Structural, magnetic, and magnetodielectric correlations in multiferroic Bi₅Ti₃FeO₁₅.

Jena, Rasmita; Chandrakanta, K.; Abdullah, Md. F.; Pal, P.; Kaushik, S. D.; Singh, A. K.

We have investigated the structural, magnetic, magnetodielectric, and magnetoimpedance characteristics of Aurivillius-structured Bi5Ti3FeO15 (BTFO) synthesized by a generic solid-state reaction route. Rietveld refinement of X-ray diffraction pattern at room temperature (RT) confirms orthorhombic crystal structure (space group A21am). In BTFO, octahedral distortion of the perovskite unit occurs due to antisite defects Fe/Ti in the BO6 site, which results in the formation of Fe–O clusters. Raman spectra also reveal Ti/FeO6 octahedral distortion due to the vibration of Bi ions in the perovskite layer. Magnetic field-dependent magnetization (M–H) and electric field-dependent polarization (P–E) measurement at RT indicate the existence of multiferroic behavior in BTFO. The M–H hysteresis at 5 K suggests that the non-interacting superparamagnetic state is dominant over the local short-range antiferromagnetic (AFM) ordering. The AFM interaction arises due to the random distribution of antisite defects Fe/Ti causing the distorted Fe–O octahedral unit. These canted spin interact via the Dzyaloshinskii–Moriya (DM) interaction. The superexchange interaction between the Fe–O–Fe ions is stronger than the next-nearest-neighboring Fe–O–O–O–Fe interaction. This happens due to the intermediate fluorite-like layer (Bi2O2)2+, which opposes the long-range exchange interaction. The negative magnetodielectric (MD) effect is more prominent at low frequency (~ 100 Hz) due to the extrinsic contribution. In contrast, in the high-frequency region (> 50 kHz), the intrinsic contribution dominates, which is further ascertained by magnetoimpedance (MI) measurement. The maximum magnitude of the MD effect is found to be ~ 0.32% at a magnetic field of 13 kOe at 150 K. Lastly, the ferroelectric characteristic of the sample is obtained from the P–E measurement with a polarization value of 4.35 µC/cm2 with an applied electric field of 70 kV/cm.

ANTISITE defects; RIETVELD refinement; DISTRIBUTION (Probability theory); DIFFRACTION patterns; RAMAN spectroscopy

Journal of Materials Science: Materials in Electronics, 2021, Vol 32, Issue 16, p21379

0957-4522

Academic Journal

10.1007/s10854-021-06641-8