Creation and amplification of electromagnon solitons by electric field in nanostructured multiferroics

Abstract

We develop a theoretical description of electro-magnon solitons in a coupled ferroelectricferromagnetic heterostructure. The solitons are considered in the weakly nonlinear limit as a modulation of plane waves corresponding to two, electric-and magnetic-like branches in the spectrum. Emphasis is put on magnetic-like envelope solitons that can be created by an alternating electric field. It is shown also that the magnetic pulses can be amplified by an electric field with a frequency close to the band edge of the magnetic branch.PACS numbers: 85.80. Jm, 77.80.Fm Multiferroic materials, i.e., materials exhibiting coupled order parameters, are in the focus of current research. These systems offer not only new opportunities for applications but also provide a test ground for addressing fundamental issues regarding the interplay between electronic correlations, symmetry, and the interrelation between magnetism and ferroelectricity [1-3]. Here we address magnetoelectrics which possess a simultaneous ferroelectric-magnetic response. A interesting aspect is the non-linear nature of the magnetoelectric excitation dynamics, which hints at the potential of these systems for exploring nonlinear wave-localization phenomena, such as multicomponent solitons [4,5], nonlinear band-gap transmission [6,7], and the interplay between the nonlinearity and Anderson localization [8]. In this paper we aim at exciting robust magnetic signals by means of electric fields. Particularly, we consider a multiferroic nano-heterostructure consisting of a ferromagnetic (FM) part deposited onto a ferroelectric (FE) substrate. As demonstrated experimentally, under favorable conditions, a coupling between the ferroelectric and the ferromagnetic order parameters may emerge (this coupling is referred to as the magnetoelectric coupling), thus allowing one to control magnetism (ferroelectricity) by means of electric (magnetic) fields. Here we consider the case when the multiferroic structure is driven by an electric field with a frequency located within the band-gap of the FE branch and in the band of the magnetic-excitation branch. For a proper choice of the electric-field frequency (that follows from the electro-magnon soliton theory developed below) it is possible to excite propagating magnetic solitons. In addition, we point out a possibility for the amplification of weak magnetic signals, which suggests the design of a digital magnetic transistor, where the role of the pump is played by the electric field.Examples of the two-phase multiferroics under study [9][10][11][12], are BaTiO 3 /CoFe 2 O 4 or PbZr 1−x Ti x O 3 /ferrites. The developed model will be applied to a system where the FE and FM regions are coupled at an interface whith a weak magnetoelectric coupling. The theory is, however, more general and can, in principle, be applied to single-phase magnetoelectrics [13][14][15]. For the creation of electro-magnon solitons, which is the subject of the present work, a two-phase multiferroic structure is more appropriate, as it allows to genera...

Magnonic Magnetoelectric Coupling in Ferroelectric/Ferromagnetic Composites

“…For propagation of the electromagnon solitons in the magnetoelectrically coupled layers, it is necessary that the electric field reaches a certain frequency-dependent amplitude, as shown in ref. [64]. This type of composite system is particularly useful for devices where a controllable amplification of the magnonic signal by an electric field is needed.…”

Magneto-electric effect for multiferroic thin film by Monte Carlo simulation

“…Recently, the magneto-electric (ME) effect in thin multiferroic films has been investigated theoretically [1][2][3][4][5][6][7][8][9] and experimentally [10,11]. Our understanding the nature of the ME effect has two origins.…”

Spin dynamics in driven composite multiferroics

“…It is an important factor during the energy transition from the driving part to the driven part. To demonstrate this behavior, we consider a simple 2-D ladder model to enhance the ME coupling phenomena at the FM/FE interface [9]. The ladder model with periodic boundary conditions is illustrated in Fig.…”

“…iron, cobalt or nickel), whereas the FE part is, for instance, BaTiO3 or PbTiO3. Recently, this type of materials has received much theoretical [2][3][4][5][6][7][8][9][10] and experimental [11,12] investigation, due to induce electric polarization (magnetization) by applying a magnetic (electric) field. This phenomenon is called the magneto-electric (ME) effect, it was first discovered by P. Curie in 1894 [13].…”