Origin and tuning of room-temperature multiferroicity in Fe-doped BaTiO3

Abstract

Simultaneous co-existence of room-temperature(T) ferromagnetism and ferroelectricity in Fe doped BaTiO3 (BTO) is intriguing, as such Fe doping into tetragonal BTO, a room-T ferroelectric (FE), results in the stabilization of its hexagonal polymorph which is FE only below ∼80K. Here, we investigate its origin and show that Fe-doped BTO has a mixed-phase room-temperature multiferroicity, where the ferromagnetism comes from the majority hexagonal phase and a minority tetragonal phase gives rise to the observed weak ferroelectricity. In order to achieve majority tetragonal phase (responsible for room-T ferroelectricity) in Fe-doped BTO, we investigate the role of different parameters which primarily control the PE hexagonal phase stability over the FE tetragonal one and identify three major factors namely, the effect of ionic size, Jahn-Teller (J-T) distortions and oxygen vacancies (OVs), to be primarily responsible. The effect of ionic size which can be qualitatively represented using the Goldschmidt's tolerance (GT) factor seems to be the major dictating factor for the hexagonal phase stability. The understanding of these factors not only enables us to control them but also, achieve suitable co-doped BTO compound with enhanced room-T multiferroic properties.

Prediction of Strong Converse Magnetoelectric Effect in Nb‐Doped BaTiO3‐Based Polar Metals

“…Moreover, theoretical work predicts that Cr-, Mn-, and Fe-doped BTO systems are essentially ferromagnetic and derived from doping atoms. [11] Many subsequent experimental studies since then confirmed the previous predictions, and room temperature FM has been reported in Mn-, [13] Fe-, [14][15][16] and Cr [17] doped BTO system. However, the ME effect of the magnetic element doped BTO system is still small.…”

“…Indeed, one of the most direct ways to achieve room-temperature ME effect is to introduce FM into the ferroelectrics through transition magnetic atom (Cr, Mn, Fe, Co, and Ni) doping. [11][12][13][14][15][16][17] BaTiO 3 (BTO) is one of the most common ferroelectrics used in the synthesis of MFs, with high dielectric constant, low dielectric loss, and lead-free. Moreover, theoretical work predicts that Cr-, Mn-, and Fe-doped BTO systems are essentially ferromagnetic and derived from doping atoms.…”

Engineering room-temperature multiferroicity in Bi and Fe codoped BaTiO3

“…Next, to study the intrinsic ferroelectric properties, we have employed the PUND 12,13 technique (for details see ref. 5 ). In Fig.3(a) we see that from x=0 there is a sudden increase in the ferroelectric polarization value for x=0.02 and then it continues to decrease up to x=0.10 [also, refer to Fig.…”

“…9 and note the discussions in subsection-C of the supplementary material below). Now, to have a holistic view, we have plotted the remanent polarization value (dPr) versus sample tolerance factor (which can strongly influence structural instabilities of such perovskite oxides 15 ) as shown in Fig.3(d), using Fe and Ti valencies determined from the Fe-K edge XANES and XPS spectroscopic studies 5 (for details, refer to subsections E-G and note Fig. 10 and Fig.…”

“…Even, the Lande g- factor for all these compounds, as shown in the bottom inset of Fig.4(d), shows similar trend like the remanent magnetization value. Such enhancement of ferromagnetism, however, can not be understood from the frame work of increasing oxygen vacancy content 19 or increasing hexagonal phase fractions, as both are simultaneously and monotonically reduced with increasing Bi doping concentration 5 . Such trends of magnetic response cannot be understood from the possible presence of any extrinsic contributions, like from BiFeO 3 , Fe 2 O 3 or Fe 3 O 4 related impurity phases, which, however, could not be detected through detailed XRD analyses, as discussed in the subsection-M of the supplementary material (also, note references [22][23][24][25] ).…”