Multiferroic and dielectric properties of Bi4LaTi3FeO15 ceramics

Crystal Chemistry and Magnetic Properties of Gd-Substituted Aurivillius-Type Bi5FeTi3O15 Ceramics

“…Both the FC and ZFC magnetizations continuously increase with decreasing temperature and show a reversible thermomagnetic behavior in the temperature range considered. In contrast to previous magnetic studies which suggested a magnetic transition in pure BFTO and rare-earth substituted BFTO compounds, 9,14,17,23,26 no magnetic anomaly related to a possible transition at cryogenic temperatures is observed in the magnetization vs temperature plots (Figure 6b). Moreover, the high-temperature VSM magnetometry showed that the paramagnetic behavior of all the samples in the Bi 5−x Gd x FeTi 3 O 15 series exists up to 700 K. Therefore, we suggest that the room-temperature (ferri/ferro/antiferro-) magnetism in BFTO previously reported in the literature might be due to the presence of magnetic impurities or shortrange ordered spins in randomly distributed Fe-rich nanoregions formed during material processing under different conditions.…”

“…As a consequence, both the unit cell volume ( V ) and orthorhombic distortion (δ = 2­( a – b )/( a + b )) are progressively reduced upon doping (see Table S1 and the inset of Figure ). These observations are in accordance with the structural studies recently reported for other rare-earth substituted Aurivillius compounds. ,, Paul et al observed similar substitution-induced relaxation of the structural distortion in the Bi 4– x Sm x Ti 3– x Fe x O 12±δ system and attributed it to different ionic radii of the substituting (Sm 3+ , Fe 3+ ) and substituted (Bi 3+ , Ti 4+ ) ions. Moreover, they found that the three-layer orthorhombically distorted system transforms to a higher symmetry tetragonal phase at a critical concentration ( x = 0.4) of the substituting elements.…”

“…Thus, the observed evolution of the Raman modes well correlates with the structural changes identified by X-ray diffraction, where the addition of Gd was found to decrease the contact angle O 8 Table S2 in the Supplementary Material). In contrast to previous magnetic studies which suggested a magnetic transition in pure BFTO and rare-earth substituted BFTO compounds 9,14,17,23,26 , no magnetic anomaly related to a possible transition at cryogenic temperatures is observed in the magnetization vs temperature plots (Fig. 6b).…”

“…These observations are in accordance with the structural studies recently reported for other rare-earth substituted Aurivillius compounds. 9,23,32 Paul et al 9 observed similar substitution-induced relaxation of the structural distortion in the Bi4-xSmxTi3-…”

“…A partial substitution of bismuth by lanthanides has been found to improve the ferroelectric properties and enhance the magnetoelectric coupling in Aurivillius multiferroics. , Peña et al have showed that rare-earth (including Gd) substituted BFTO ceramics are isostructural with pure BFTO and exhibit a paramagnetic behavior at and below room temperature. On the other hand, Huang et al reported a weakly ferromagnetic state in Nd-modified BFTO at room temperature.…”