Intrinsic multiferroics in an individual single-crystalline Bi₅Fe_0.9Co_0.1Ti₃O₁₅ nanoplate

Abstract

In recent years, much attention has been paid to layer-structured BiBiFeMTiO (BFMTO, M = Co, Mn) compounds due to their potential as high temperature single phase multiferroic materials. However, BFMTO single crystals have been rarely reported in the past, though they are better candidates for studying the corresponding intrinsic multiferroics as well as the platform for making future devices, due to their structural complexity and difficulties in fabrication. In this article, BiFeCoTiO single-crystalline nanoplates were synthesized by the hydrothermal method. The ferromagnetic domain structure of the nanoplate was investigated by electron holography. Denser phase contours were observed and the closed magnetic flux lines indicated a significant magnetic interaction between the neighboring nanoplates, which proved the ferromagnetic nature of the sample. Furthermore, M-H loops of the sample were also measured, in which the ferromagnetic Curie temperature reached ∼730.2 K. Besides, ferroelectric domains were also detected by using a piezoresponse force microscope. All the above-mentioned results indicate the first verification of the room temperature (RT) multiferroic behaviour in such single crystals, which will be useful for both future devices and understanding the underlining physics.

Progress and Perspectives on Aurivillius-Type Layered Ferroelectric Oxides in Binary Bi4Ti3O12-BiFeO3 System for Multifunctional Applications

“…Because of specific surface effect, small size effect, quantum effect, etc., the nanophase materials show manifold excellent performances and have broad applications in the fields of environmental pollution and shortage of clean energy. So, the BFTO-n in the form of nanostructure attracted extensive attention worldwide in recent years and diverse nanostructures of them including nano-shelves [54], nano-belts [97,98], nano-fibers [63], nano-sheets [62], nano-plates [59], and nano-flowers [53] were synthesized and applied as catalysts for photo-degradation, visible-light-driven water splitting, and oxygen evolution reaction. Morphology of the BFTO-n nanobelts synthesized via electrospinning is shown in Figure 4e.…”

“…The selected area electron diffraction (SAED) patterns taken from four corns of one BFTO plate from the sample in Figure 4h exhibit almost identical diffraction spots corresponding to (200) and (020) plane, confirming the single-crystalline nature (Figure 4i). More importantly, this individual single-crystalline nanoplate can verify intrinsic FM and FE properties of Aurivillius-type BFTO-n compounds [59]. Apart from the nano-crystals, single crystals of the BFTO-n were grown by using modified micro-pulling down method [60].…”

“…In addition, it is necessary to mention that despite there are some controversies about the origin of magnetism in the early days [128][129][130], the intrinsic RT magnetism properties of Mn-, Ni-, and Co-doped BFTO-n were clearly determined by impedance spectroscopy [131], magnetic domain investigations [67], magnetic thermogravimetric analysis [132], and polarized neutron reflectivity [133]. Moreover, the intrinsic FM nature of individual single-crystalline Bi 5 Fe 0.9 Co 0.1 Ti 3 O 15 nanoplate was visualized by electron holography [59].…”

“…In the last decade, numerous pieces of research focused on the BFTO-n with integer n, for example, Bi 5 FeTi 3 O 15 , Bi 6 Fe 2 Ti 3 O 18 , and Bi 7 Fe 3 Ti 3 O 21 . The reported studies have mainly embodied two aspects: (i) doping ions into A-sites [19][20][21][22][23][24][25][26][27][28][29] and/or substituting magnetic transition ions into B-sites [30][31][32][33][34][35][36][37][38][39][40][41][42][43] inside the layered perovskite structure to realize a significant enhancement in the multiferroic performances, and (ii) controllable synthesis of materials in ceramics [44][45][46], thin films [47][48][49][50][51][52], nano-crystallines [53][54][55][56][57][58] and single crystals [59][60][61] to observe the growth process [62][63][64]…”

Extended Near-Infrared Photoactivity of Bi6Fe1.9Co0.1Ti3O18 by Upconversion Nanoparticles

“…Recently, layered bismuth-based Bi 4 Bi n −3 Fe n −3− x Co x Ti 3 O 3 n +3 (BFCTO) Aurivillius compounds, which are formed by perovskite-type (Bi n −1 Fe n −3− x Co x Ti 3 O 3 n +1 ) 2− blocks sandwiched between fluorite-type (Bi 2 O 2 ) 2+ slabs, where n is the number of perovskite units per half-cell [18,19,20,21], proved to be apotential single-phase multiferroic material with ferroelectricity and ferromagnetism [22]. Moreover, the internal electric field and ferromagnetism could enable the photocatalysts recyclable in viscous solution, which is important but extremely difficult due to their size and high viscosity [23].…”