Structure and spin dynamics of multiferroic BiFeO₃

Abstract

Multiferroic materials have attracted much interest due to the unusual coexistence of ferroelectric and (anti-)ferromagnetic ground states in a single compound. They offer an exciting platform for new physics and potentially novel devices. BiFeO3 is one of the most celebrated multiferroic materials and has highly desirable properties. It is the only known room-temperature multiferroic with TC ≈ 1100 K and TN ≈ 650 K, and exhibits one of the largest spontaneous electric polarisations, P ≈ 80 µC cm(-2). At the same time, it has a magnetic cycloid structure with an extremely long period of 620 Å, which arises from competition between the usual symmetric exchange interaction and the antisymmetric Dzyaloshinskii-Moriya (DM) interaction. There is also an intriguing interplay between the DM interaction and single ion anisotropy K. In this review, we have attempted to paint a complete picture of bulk BiFeO3 by summarising the structural and dynamic properties of both the spin and lattice parts and their magneto-electric coupling.

Spin and lattice excitations of aBiFeO3thin film and ceramics

“…It is worth noting that according to a recent symmetry analysis, 36 BiFeO 3 allows directional dichroism and therefore spin waves can be simultaneously excited by the electric and magnetic components of electromagnetic radiation. For more details on BiFeO 3 spin dynamics, see the review of Park et al 37 In the current work, we report spin and lattice excitations in BiFeO 3 ceramics, as measured by the combination of IR reflectivity and time-domain THz transmission spectroscopy, in a temperature range from 10 to 900 K. All 13 IR-active phonon modes are observed, exhibiting softening on heating. Five low-frequency spin modes are detected from 5 K up to RT, the highest two appearing at 53 and 56 cm −1 .…”

Synthesis, structures and properties of single phase BiFeO3 and Bi2Fe4O9 powders by hydrothermal method

“…BiFeO 3 is one of the most outstanding multiferroic materials with coexisted ferroelectric (Curie temperature T c * 1103 K) and antiferromagnetic (Néel temperature T N * 643 K) orders. BiFeO 3 has been investigated in many forms [1][2][3]. On the other hand, Bi 2 Fe 4 O 9 is generally easy to be formed as the second phase during the process of preparing BiFeO 3 powder or ceramics, making the phase purity of BiFeO 3 to be very processing-sensitive [4].…”

The birth of time‐of‐flight (TOF) neutron powder diffraction at pulsed neutron source (invited)

“…The spiral ordering in BiFeO 3 complicates applications of this material in electronic devices. A review on BiFeO 3 structural properties has been recently published [41].…”