Emergence of two-magnon modes below spin-reorientation transition and phonon-magnon coupling in bulk BiFeO3: An infrared spectroscopic study

Low Temperature Magnetic Transition of BiFeO3 Ceramics Sintered by Electric Field-Assisted Methods: Flash and Spark Plasma Sintering

“…The irreversibility of magnetization was evidenced at temperatures below 100 K, i.e., the ZFC and FC curves split below this temperature. Such splitting phenomena is commonly attributed to ferromagnetic and antiferromagnetic interfaces [26], and it has been observed in other BiFeO3-related compounds [15,27,36,37]. As can be seen, this phenomenon is more remarkable for the BiFeO3 nanoceramic samples sintered by SPS and FS as compared to the sample prepared by SSR.…”

“…The analysis of the phase transition behavior in BiFeO 3 is commonly focused on a hightemperature regime and the nature of phase transitions below 300 K remain unclear. In this sense, magnetic measurements on single crystals, powders or nanostructured BiFeO 3 have exposed different magnetic transitions within this temperature range [26][27][28]. Moreover, different experimental techniques, such as calorimetry, dielectric or mechanical measurements, as well as Raman spectroscopy have reported possible phase transitions close to 25,38,55,140,150,178,200 and 230-260 K [29][30][31], assigned to different phenomena, such as magnetic but glassy transitions (38-50 K), or magnetoelastic transition around 200-220 K. Therefore, it is of the most interest to perform more studies on the low-temperature regime in order to clarify the nature of the observed transitions.…”

Interplay of piezoresponse and magnetic behavior in Bi0.9A0.1FeO2.95 (A = Ba, Ca) and Bi0.9Ba0.05Ca0.05FeO2.95 co-doped ceramics

“…From our recent magnetic studies, the ceramic BiFeO 3 sample was found to develop weak ferromagnetic order at low-temperature. 38,39 This improvement in the magnetic property was understood through the destruction of the cycloidal spin structure driven by an increase in single ion anisotropy and anharmonicity of the spin cycloid, 40 as was evidenced from the direct observation of a partial suppression of the spin wave excitations from our far-infrared reectance measurements at low temperature. 41 A similar mechanism could be at play in the doped BiFeO 3 system as well.…”

“…Post polishing, the pellets were heated at 400 C for 4 hours in order to remove any surface residual stress that may have been generated due to the mechanical polishing process. The high quality of the samples were also established from the infrared reectance spectra of these samples, 37,39 wherein we could observe all the allowed phonon modes (4A 1 + 9E) corresponding to the rhombohedral phase, with no trace of any impurity phase. From Rietveld renement of the X-ray diffraction patterns of these samples, a reduction of unit cell volume is observed in all the doped samples compared to the pristine sample.…”

Influence of Ca doping on X‐ray photoelectron core‐level spectra of magnetoelectric bulk BiFeO3

“…With this background, in the present work, we wanted to investigate the core‐level XPS spectra of pristine and alkali‐earth‐metal (Ca and/or Ba) doped BiFeO 3 ceramic samples. Notably, in our earlier works, the physical properties and structure–property correlations of these samples were investigated and the details can be seen somewhere else 5,6,26–32 . Above all, the enhanced magnetic/magnetoelectric properties were detected for the Ca‐doped and Ba‐Ca co‐doped BiFeO 3 compounds, 6,29,31,33 ascribed to the chemical pressure induced by Ca doping.…”