Features of the magnetoelectric properties of BiFeO3 in high magnetic fields

Abstract

It is shown that the destruction of the cycloidal structure of the magnetic ferroelectric BiFeO3 by a high magnetic field (Hn≈200 kOe) leads to the onset of a linear magnetoelectric effect and the appearance of a toroidal moment. The proof of the existence of a toroidal moment T in a high magnetic field (H>Hn) is based on the experimental observation that the off-diagonal components of the linear ME effect tensor are asymmetric (α12=−α21 for L‖c, where L is the antiferromagnetic vector), inasmuch as Tz∼α12−α21.

Phase transitions in multiferroic BiFeO3crystals, thin-layers, and ceramics: enduring potential for a single phase, room-temperature magnetoelectric ‘holy grail’

“…Using such a field orientation, it is possible to measure both polarization components P a (H) and P b (H). A nonzero antisymmetric component in the magnetoelectric tensor (6) appears for H>H c , evidencing a toroidal moment T z~( α 12 -α 21 ) upon inducing the homogeneous spin state [4,7]. [51].…”

“…Above this critical point, a transition will occur to a homogenous antiferromagnetic spin state: consequently, all of the latent properties of bismuth ferrite hidden by the cycloid -such as linear magnetoelectric effect, spontaneous polarization, and toroidal moment -should become apparent. We will first show experimental evidence from a series of magnetic, magnetoelectric, magnetic resonance studies under high magnetic fields [4,7,28,29,51] that demonstrate such a spin transformation. Then, we will provide theoretical grounds for understanding the transition.…”

“…However, on the other hand, its unusual magnetic symmetry properties (space and time symmetry violation both in its crystal and magnetic structures) results in a variety of nontrivial consequences, including: (i) the unique coexistence of weak ferromagnetism and linear magnetoelectricity [3,4]; (ii) a toroidal moment, i.e., a special magnetic type of ordering [5][6][7][8]; (iii) the existence of an incommensurately modulated spin structure [9], previously only observed in magnetic metals; and (iv) magnetically induced optical second harmonic generation, observed for the first time in this particular material [10]. Furthermore, BiFeO 3 is the material with unique high ferroelectric Curie (T C =1083 K) [11] and antiferromagnetic Neel (T N =643K) [12] temperatures.…”

Destruction of spin cycloid in (111)c-oriented BiFeO3 thin films by epitiaxial constraint: Enhanced polarization and release of latent magnetization

“…11,13 The antiferromagnetic vector is locked within the cycloid, averaged to zero over . 14,15 This latent magnetization can be released by application of high magnetic fields. 16 Recent electron spin resonance investigations have also shown an induced phase transition from cycloidal to homogeneous antiferromagnetic spin orders for H Ͼ 18 T. 17 This induced phase transition can be understood by the following Landau-Ginzburg ͑LG͒ theory: [14][15][16][17][18] F homogeneous Ͻ F cycloid , ͑1a͒…”

Исследование мультиферроиков BiFe-=SUB=-1-x-=/SUB=-Cr-=SUB=-x-=/SUB=-O-=SUB=-3-=/SUB=- (x=0-0.20) методом эффекта Мессбауэра

“…Разрушение или подавление гармоничности циклоиды ПСМС, например, внешним магнитным полем 200 kOe приводит к росту намагниченности и появлению линейного магнитоэлектрического эффекта [7]. Улучше-ние магнитоэлектрических свойств в мультиферроиках на основе BiFeO 3 достигается также при замещении катионов Bi или Fe катионами различных групп перио-дической таблицы элементов (см., например, [8][9][10]).…”