Size effects of ferroelectric and magnetoelectric properties of semi-ellipsoidal bismuth ferrite nanoparticles

Abstract

Bismuth ferrite (BiFeO 3 ) is one of the most promising multiferroics with a sufficiently high ferroelectric (FE) and antiferromagnetic transition temperatures, and magnetoelectric (ME) coupling coefficient at room temperature, and thus it is highly sensitive to the impact of cross-influence of applied electric and magnetic fields. According to the urgent demands of nanotechnology miniaturization for ultra-high density data storage in advanced nonvolatile memory cells, it is very important to reduce the sizes of multiferroic nanoparticles in the self-assembled arrays without serious deterioration of their properties. We study size effects of the phase diagrams, FE and ME properties of semi-ellipsoidal BiFeO 3 nanoparticles clamped to a rigid conductive substrate. The spatial distribution of the spontaneous polarization vector inside the nanoparticles, phase diagrams and paramagnetoelectric (PME) coefficient were calculated in the framework of modified Landau-Ginzburg-Devonshire (LGD) approach. Analytical expressions were derived for the dependences of the FE transition temperature, average polarization, linear dielectric susceptibility and PME coefficient on the particle sizes for a general case of a semi-ellipsoidal nanoparticles with three different semi-axes a, b and height c. The analyses of the obtained results leads to the conclusion that the size effect of the phase diagrams, spontaneous polarization and PME coefficient is rather sensitive to the particle sizes aspect ratio in the polarization direction, and less sensitive to the absolute values of the sizes per se.

Renovation of Interest in the Magnetoelectric Effect in Nanoferroics

“…All that stimulated us to study the influence of size effects on the FE, AFE, and ME properties of semiellipsoidal BiFeO 3 nanoparticles theoretically, in the framework of the Landau-Ginzburg-Devonshire approach, classical electrostatics, and elasticity theory [128]. Ferroelectricity is known to be a phenomenon associated with the long-range ordering of dipole moments.…”

“…If the magnetization M is proportional to the applied magnetic field H, i.e. ≈ FM ( ) , the PME coefficient has the form [128]…”

Analytical description of domain morphology and phase diagrams of ferroelectric nanoparticles

“…The continuum phenomenological Landau-Ginzburg-Devonshire (LGD) approach combined with the electrostatic equations allows one to establish the physical origin of the anomalies in the polar and dielectric properties, and calculate the phase diagrams changes appearing under the decrease of ferroelectric particle sizes. For instance, using the LGD approach Niepce [20], Huang et al [21,22], Glinchuk et al [23,24], Ma [25], Khist et al [26], Wang et al [27], Morozovska et al [28,29,30,31] and Eliseev et al [32,33,34] have shown, that the changes of the transition temperatures, enhancement or weakening of spontaneous polar or/and magnetic order in a single-domain spherical, ellipsoidal and cylindrical nanoparticles of sizes (4 -100 nm) are conditioned by the various physical mechanisms, such as surface tension, correlation effect, depolarization field, flexoelectricity, electrostriction, magnetoelectric coupling, magnetostriction, rotostriction and Vegard-type chemical pressure. We emphasize that the applicability of the LGD approach for ferroelectric nanoparticles with sizes about (4-5) nm or more (i.e.…”

“…Incomplete screening of spontaneous polarization causes depolarization fields, which in turn can lead to appearance of ferroelectric domains in the particle, decreasing the positive energy of depolarization field [26,27,33,34,44]. Incomplete screening conditions of the spontaneous polarization also leads to the decrease of ferroelectric transition temperature due to the depolarization field effect [26,27,33,34]. Yet the vast majority of theoretical models (both LGD-based and ab initio) consider the particles covered with perfect electrodes, stabilizing their single-domain state (see e.g.…”

Influence of Oxygen Pressure on the Domain Dynamics and Local Electrical Properties of BiFe0.95Mn0.05O3 Thin Films Studied by Piezoresponse Force Microscopy and Conductive Atomic Force Microscopy

“…These properties facilitate the magnetic (spin) state control by electric fields, with some having the potential to be used in multistate logic sensors, non-volatile memories, solid-state transformers, and electromagneto-optic actuators [1,2,3,4,5,6]. Among multiferroic materials, BiFeO 3 (BFO) has been intensively investigated due to its unique characteristics of a high ferroelectric–paraelectric transition temperature ( T C ) of approximately 1083 K, and high antiferromagnetic to paramagnetic Néel temperature ( T N ) of approximately 625 K [7,8,9,10]. However, it is well known that BFO causes high leakage currents and magnetic measurement errors that have been attributed to specific structural defects [11,12,13,14].…”