Enhanced Magnetization and Modulated Orbital Hybridization in Epitaxially Constrained BiFeO₃ Thin Films with Rhombohedral Symmetry

Abstract

BiFeO3 (BFO) is currently considered to be the most promising candidate material for device applications of room-temperature multiferroics. However, there exist some controversial arguments on the origin of the enhanced magnetization and polarization observed in the epitaxially constrained BFO thin film heterostructures. More specifically, the issue can be addressed by the following question: Can the epitaxial strain enhance the magnetization and the ferroelectric polarization in BFO? To clarify this controversial issue, we have systematically examined the magnetization characteristics of the rhombohedral BFO films epitaxially grown on (111)-oriented SrTiO3 (STO) in terms of the in-plane misfit strain between the BFO layer and the STO substrate. The increase in the saturation magnetization with decreasing film thickness was found to be closely related with the misfit strain. By carefully examining synchrotron X-ray absorption spectra, we have further correlated the enhanced magnetization in a highly strained film with the reduced degree of hybridization between Fe 3d and O 2p orbitals and with the splitting of the triplet t2g orbital into a1g and eg π orbitals arising from the trigonal D 3d distortion.

Crystal structure and magnetic properties of the BaFe12−Al O19 (x=0.1–1.2) solid solutions

“…Because the multiferroism at room temperature is an essential issue for the realization of multiferroic devices that exploit the coupling between ferroelectric and ferromagnetic orders at ambient conditions, BiFeO 3 [12] together with recently investigated LuFe 2 O 4 [13], Pb 2 Fe 2 O 5 [14] and PbFe 12 O 19 [15] is currently considered to be promising candidates for device applications. The perovskite BiFeO 3 [12] shows weak magnetism, which somehow limit its practical application. Therefore, preparation of a material in which large ferroelectricity and strong ferromagnetism coexist would be a milestone for modern electrics and functionalized materials [16].…”

Structure and multiferroic properties of barium hexaferrite ceramics

“…However, materials in which ferroelectricity and ferromagnetism coexist are rare [3,4] and mostly provide rather weak ferromagnetism. Because the multiferroism at room temperature is an essential issue for the realization of multiferroic devices that exploit the coupling between ferroelectric and ferromagnetic orders at ambient conditions, BiFeO 3 together with more recently developed LuFe 2 O 4 , Pb 2 Fe 2 O 5 and PbFe 12 O 19 [5][6][7][8][9] are currently considered to be promising candidates for device applications. The perovskite BiFeO 3 shows weak magnetism, which could somehow limit its practical application.…”

Multiferroic PbFe12O19 ceramics

“…Because the room-temperature multiferroism is essential to the realization of multiferroic devices that exploit the coupling between ferroelectric and ferromagnetic orders at ambient conditions, BiFeO 3 together with more recently revealed LuFe 2 O 4 [6][7][8][9][10][11] are currently considered to be promising candidates for practical device applications. The perovskite BiFeO 3 is ferroelectric (Tc1 103 K) and antiferromagnetism (T N~6 43 K), exhibiting weak magnetism at room temperature due to a residual moment from a canted spin structure [12], which could somehow prevent its practical application.…”