Magnetoelectric Systems Research Articles

On the Origin of Signal and Bandwidth of Converse Magnetoelectric Magnetic Field Sensors

AbstractConverse magnetoelectric sensors enable the detection of low‐frequency and low‐amplitude magnetic fields over a bandwidth of several kilohertz by combining the electrical excitation of a magnetoelectric resonator via a piezoelectric layer with an inductive readout. Here, a comprehensive sensor model is presented to further foster the development of this promising sensor concept. The model relates the output signal to the device characteristics, taking into account the magnetoelastic and electromechanical properties, the resonator geometry, and operating conditions. The sensor system is thoroughly experimentally analyzed to validate the model. Based on the analysis, the sensor concept is explained in detail, including the origin of its loss and bandwidth and their connection with the magneto‐mechanical loss in the magnetostrictive layer. Significant advances have been made in the comprehensive understanding of converse magnetoelectric sensors, providing a solid basis for future improvements in magnetoelectric sensor systems.

Development and possible applications of tunable elements based on composite materials

This work is devoted to the synthesis of nano-sized weakly agglomerated magnetic particles with different crystal structures, which were used in the development of nonlinear composite structures, in particular, nonlinear resonant microwave elements, left-handed media, and nonlinear magnetoelectric systems.

Perspectives: Light Control of Magnetism and Device Development.

Accurately controlling magnetic and spin states presents a significant challenge in spintronics, especially as demands for higher data storage density and increased processing speeds grow. Approaches such as light control are gradually supplanting traditional magnetic field methods. Traditionally, the modulation of magnetism was predominantly achieved through polarized light with the help of ultrafast light technologies. With the growing demand for energy efficiency and multifunctionality in spintronic devices, integrating photovoltaic materials into magnetoelectric systems has introduced more physical effects. This development suggests that sunlight will play an increasingly pivotal role in manipulating spin orientation in the future. This review introduces and concludes the influence of various light types on magnetism, exploring mechanisms such as magneto-optical (MO) effects, light-induced magnetic phase transitions, and spin photovoltaic effects. This review briefly summarizes recent advancements in the light control of magnetism, especially sunlight, and their potential applications, providing an optimistic perspective on future research directions in this area.

Computational design of the novel Fe-doped single-layer SrS: structural, electro-magnetic, and optical properties.

The search for novel intrinsic two-dimensional (2D) magnetic materials is crucial to understand the fundamentals of 2D magnetism and realize next-generation magneto-electric and magneto-optical systems. Using the rigorous framework of spin-polarized density functional theory (SPDFT)-based ab initio calculations, this investigation systematically investigates the effects of a stepwise change in the Fe composition (x) on the structural, electro-magnetic and optical properties of the ordered SrS based single-layer alloys, with x encompassing values from 0 to 1. Our comprehensive analysis revealed that the calculated formation energies, cohesive energies, phonon dispersions, molecular dynamics, and elastic constants of both bare SrS and FeS monolayers indicate their thermodynamic, dynamic, thermal, and mechanical stability in hexagonal and square structures, respectively. Significantly, the introduction of magnetic Fe dopants into the non-magnetic SrS semiconductor enabled the creation of an intrinsic magnetic (FM) state characterized by spin-polarized charge carriers at the Fermi level (E F). As doping increases, the electronic structure shows a noticeable dependence on the chemical composition. It is noteworthy that the systems doped with 0.750 and 1 Fe exhibit metallic-magnetic and metallic non-magnetic properties, respectively, and the rest are half-semiconductors (HSC) according to the GGA approximation. Conversely, the HSE approach shows a transition to HSC for a doping level of 0.750, while others maintain the same behavior. The study of the optical properties shows improvements compared to the bare SrS monolayer through the incorporation of Fe dopants. The bare SrS has light absorption in the ultraviolet region, while the absorption band edges for HSC compounds change from the infrared to visible regions. This study proposes a practical method to tune the properties of the SrS single-layer by selectively adjusting the dopant concentration. Such control is promising for applications in spintronics and optical based nanodevices.

Robust multiferroicity and magnetic modulation of the ferroelectric imprint field in heterostructures comprising epitaxial Hf0.5Zr0.5O2 and Co.

Magnetoelectric multiferroics, either single-phase or composites comprising ferroelectric/ferromagnetic coupled films, are promising candidates for energy efficient memory computing. However, most of the multiferroic magnetoelectric systems studied so far are based on materials that are not compatible with industrial processes. Doped hafnia is emerging as one of the few CMOS-compatible ferroelectric materials. Thus, it is highly relevant to study the integration of ferroelectric hafnia into multiferroic systems. In particular, ferroelectricity in hafnia, and the eventual magnetoelectric coupling when ferromagnetic layers are grown atop of it, are very much dependent on quality of interfaces. Since magnetic metals frequently exhibit noticeable reactivity when grown onto oxides, it is expected that ferroelectricity and magnetoelectricity might be reduced in multiferroic hafnia-based structures. In this article, we present excellent ferroelectric endurance and retention in epitaxial Hf0.5Zr0.5O2 films grown on buffered silicon using Co as the top electrode. The crucial influence of a thin Pt capping layer grown on top of Co on the ferroelectric functional characteristics is revealed by contrasting the utilization of Pt-capped Co, non-capped Co and Pt. Magnetic control of the imprint electric field (up to 40% modulation) is achieved in Pt-capped Co/Hf0.5Zr0.5O2 structures, although this does not lead to appreciable tuning of the ferroelectric polarization, as a result of its high stability. Computation of piezoelectric and flexoelectric strain-mediated mechanisms of the observed magnetoelectric coupling reveal that flexoelectric contributions are likely to be at the origin of the large imprint electric field variation.

Dynamic Pluronic F127 Crosslinking Enhancement of Biopolymeric Nanocomposites for Piezo-Triboelectric Single-Hybrid Nanogenerators and Self-Powered Sensors.

Biomechanical and nanomechanical energy harvesting systems have gained a wealth of interest, resulting in a plethora of research into the development of biopolymeric-based devices as sustainable alternatives. Piezoelectric, triboelectric, and hybrid nanogenerator devices for electrical applications are engineered and fabricated using innovative, sustainable, facile-approach flexible composite films with high performance based on bacterial cellulose and BaTiO3 , intrinsically and structurally enhanced by Pluronic F127, a micellar cross-linker. The voltage and current outputs of the modified versions with multiwalled carbon nanotube as a conductivity enhancer and post-poling effect are 38V and 2.8µA cm-2 , respectively. The multiconnective devices' power density can approach 10 µW cm-2 . The rectified output power is capable of charging capacitors, driving light-emitting diode lights, powering a digital watch and interfacing with a commercial microcontroller board to operate as a piezoresistive force sensor switch as a proof of concept. Magnetoelectric studies show that the composites have the potential to be incorporated into magnetoelectric systems. The biopolymeric composites prove to be desirable candidates for multifunctional energy harvesters and electronic devices.

Recent Development of Flexible Magnetoelectric Material Systems and Related Additive Manufacturing Techniques

Recent Development of Flexible Magnetoelectric Material Systems and Related Additive Manufacturing Techniques

A Miniaturized Conduction-Cooled HTS Magnet for Space Magnetoelectric Thruster

Superconducting magnet is the key component used as the magnetic nozzle to improve the performance of the magnetoelectric thruster. Compared to the traditional copper or permanent magnet, it has high current density and uniform characteristics. Based on space application requirements of the magnetic nozzle for magnetoelectric thruster, a miniaturized high-temperature superconducting magnet structure is proposed in this article. The Stirling conduction-cooling method is used to replace the conventional GM cryocooler cooling method with a large compressor to realize the miniaturization of the magnet system. When the operating current is 1.5 times that of the maximum design current (40 A), the stability margin of the magnet is still more than 1000 mJ/cc. In addition, according to the calculation of ac loss, the magnet does not undergo quenching up until 254 Hz, which further demonstrates the safety and stability characteristics of the magnet. Finally, during a low-temperature (∼50 K) experiment, the magnet can maintain stable operation for more than 3 h while the temperature rise is less than 0.35 K, which confirms the feasibility of the miniaturized conduction-cooled scheme proposed in this article. This article lays a technical foundation for the future space application of high-power magnetoelectric propulsion systems.

Strain and charge contributions to the magnetoelectric coupling in Fe3O4/PMN-PT artificial multiferroic heterostructures

The quest to realize new kinds of data storage devices has motivated recent studies in the field of magnetoelectric heterostructures. One of the most commonly investigated systems is Fe3O4/[Pb(MgNbO3]0.7–[PbTiO3]0.3 (PMN-PT), however, the interplay between different coupling mechanisms is not yet well understood. To disentangle the role of strain and polarisation influence in Fe3O4/PMN-PT, we report on magnetoelectric coupling measurements for different orientations of the applied magnetic field and for two different substrate cuts, PMN-PT(001) and PMN-PT(011). For Fe3O4/PMN-PT(011), having the sample aligned such that the magnetic field is parallel to the [01] easy axis leads to a remanent increase of the magnetisation for each electric field cycle. On the other hand, for the magnetic field along the [100] hard axis, the magnetisation follows a butterfly-like loop characteristic of strain coupling imparted by the substrate. For Fe3O4/PMN-PT(001), the magnetoelectric effect is a superposition of the observed behaviour of both in-plane directions in Fe3O4/PMN-PT(011). The magnetisation shows an initial remanent increase followed by a butterfly like loop. Polarised neutron reflectometry measurements on Fe3O4/PMN-PT(011) shows no difference between the behaviour at the interface and the bulk of the film and no decline of the interaction further away from the shared interface. Our results demonstrate the role of strain and polarisation on the magnetisation of the Fe3O4 layer and provide a clear step towards the design of future magnetoelectric systems.

In a search for effective giant magnetoelectric coupling: Magnetically induced elastic resonance in Ni-Mn-Ga/P(VDF-TrFE) composites

Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) is a piezoelectric polymer suitable for applications in electromechanical and magnetoelectric (ME) systems. Ni-Mn-Ga alloys exhibit a giant magnetoelastic response related to their structural transformations of martensitic type, accompanied by noticeable volume changes. Together, in a thin film composite containing an ensemble of Ni-Mn-Ga particles (10 wt.%) distributed in the P(VDF-TrFE) piezopolymer, they ensure an unprecedented resonance amplification of the ME effect. Thus, a giant value of ME coefficient of 6.05 V·cm−1· Oe−1 under AC magnetic drive field of 0.2 Oe and DC bias field of 1300 Oe is experimentally observed and discussed. The physical mechanism of the proposed ME response amplification has been explained theoretically through the volume magnetostriction of the magnetostrictive particles and resonant elastic oscillation of the piezoelectric polymer matrix.

Investigation of Local Piezo- and Ferroelectric Properties in a Single-Ion Zn/Dy Molecular Complex

In this work, the piezoelectric and ferroelectric properties in the Zn/Dy single-ion molecular complex have been studied by local piezoresponse force microscopy and switching spectroscopy. It is demonstrated that the chosen strategy for the synthesis of integrated magnetoelectric molecular systems makes it possible to grow molecular single crystals in the polar group. Switching of the intrinsic domain structure in Zn/Dy single crystal at a bias voltage of +15 V and the possibility of changing the induced domain structure at a bias voltage of -20 V were demonstrated. The effective piezoelectric coefficient d33 was attained of about 14 pm/V at a bias voltage of 50 V. Keywords: Integrated magnetoelectric molecular systems, magnetoelectric interaction, single-ion molecular chiral complex, piezoresponse force microscopy (PFM).

Исследование локальных пьезо- и сегнетоэлектрических свойств в одноионном молекулярном комплексе Zn/Dy

In this work, the piezoelectric and ferroelectric properties in the Zn/Dy single-ion molecular complex have been studied by local piezoresponse force microscopy and switching spectroscopy. It is demonstrated that the chosen strategy for the synthesis of integrated magnetoelectric molecular systems makes it possible to grow molecular single crystals in the polar group. Switching of the intrinsic domain structure in Zn/Dy single crystal at a bias voltage of +15 V and the possibility of changing the induced domain structure at a bias voltage of -20 V were demonstrated. The effective piezoelectric coefficient d33 was attained of about 14 pm/V at a bias voltage of 50 V.

(Invited) Magnetoelectrics at Nanometer and Gigahertz Scales for Advanced Spintronic Computing Applications

Since the work of Oersted and Ampère in the early 19th century, magnetism and magnetic fields have been connected to electric currents. By contrast, the control of magnetism by electric fields has elicited interest in the scientific and engineering communities only much more recently. Although originally postulated by Pierre Curie in 1894 and later discussed in more detail by Debye in the 1920s, the first experimental demonstration of a magnetoelectric effect occurred only in 1960. While single phase multiferroic materials were initially at the center of interest, the focus shifted rapidly in the 1970s towards magnetoelectric compound materials that offer larger magnetoelectric coupling strengths. Recently, magnetoelectricity has seen a renaissance due to both technological and theoretical progress [1,2]. The main interest in magnetoelectric systems lies in the potentially much higher energy efficiency with respect to current- and even current-density-based magnetization control. Therefore, magnetoelectricity may become an enabling step for novel low-power spintronic devices [3,4].Magnetoelectric compound materials are layered composites that consist of piezoelectric and magnetostrictive films. The magnetoelectric coupling occurs via strain: applying an electric field across the piezoelectric generates strain, which is then transferred to the adjacent magnetostrictive. This leads to an effective magnetic field that can influence the magnetization of the system. An analogous inverse effect exists also that links changes in the magnetization direction to electric fields. Since the coupling between voltage and strain in piezoelectric films can be efficient, magnetoelectric composites are promising as transducers between electric and magnetic domains with high energy efficiency and large output signal.For microelectronic applications, magnetoelectric composites must be integrated into devices and miniaturized to the nanoscale. In this presentation, we review our recent work on submicron magnetoelectric devices and discuss the effect of scale on the voltage coupling. We demonstrate that the miniaturization can lead to an enormous increase in the voltage response of magnetoelectric structures. Moreover, many applications require fast responses of the devices with targeted operational frequencies in the GHz range. Such high frequencies can strongly modify the mode of operation of magnetoelectric devices since the coupling may now occur between acoustic waves or resonator modes in nanoscale devices and dynamic magnetic excitation, such as ferromagnetic resonance or spin waves [5,6]. We introduce the basic concepts of magnetoelectric spin wave transducers and demonstrate their operation. Finally, we discuss the potential of magnetoelectric transducers for spin wave computing applications [7].This work has been funded by the European Union’s Horizon 2020 research and innovation program within the FET-OPEN Project CHIRON under Grant Agreement No. 801055as well as by imec’s industrial affiliate program on beyond-CMOS logic.[1] M. Fiebig, J. Physics D: Appl. Phys. 38, R123 (2005).[2] G. Srinivasan, S. Priya, N. Sun, Composite Magnetoelectrics: Materials, Structures, and Applications, (Woodhead Publishing, Boston, MA, 2015).[3] S. Manipatruni, D.E. Nikonov, I.A. Young, Nature Phys. 14, 338 (2018).[4] S. Manipatruni, D.E. Nikonov, C.-C. Lin, T.A. Gosavi, H. Liu, B. Prasad, Y.-L. Huang, E. Bonturim, R. Ramesh, I.A. Young, Nature 565, 35 (2019).[5] F. Vanderveken, H. Ahmad, M. Heyns, B. Sorée, C. Adelmann, F. Ciubotaru, J. Phys. D: Appl. Phys. 53, 495006 (2020).[6] F. Vanderveken, J. Mulkers, J. Leliaert, B. Van Waeyenberge, B. Sorée, O. Zografos, F. Ciubotaru, C. Adelmann, Phys. Rev. B. 103, 054439 (2021).[7] A. Mahmoud, F. Ciubotaru, F. Vanderveken, A.V. Chumak, S. Hamdioui, C. Adelmann, S. Cotofana, J. Appl. Phys. 128, 161101 (2020).Figure: Top: Schematic of a nanoscale magnetoelectric spin wave transducer on top of a magnetostrictive waveguide including simulated strain tensor components due to resonator modes at 10 GHz. Bottom: Micromagnetic simulation results of the magnetization dynamics generated by a magnetoelectric transducers at 10 GHz [5]. Figure 1

Unusual anisotropic magnetic orbital moment obtained from x-ray magnetic circular dichroism in a multiferroic oxide system

The electric-field control of $d$-electron magnetism in multiferroic transition metal oxides is attracting widespread interest for the underlying fundamental physics and for next generation spintronic devices. Here, we report an extensive study of the $3d$ magnetism in magnetoelectric Ga$_{0.6}$Fe$_{1.4}$O$_3$ (GFO) epitaxial films by polarization dependent x-ray absorption spectroscopy. We found a non-zero integral of the x-ray magnetic circular dichroism, with a sign depending upon the relative orientation between the external magnetic field and the crystallographic axes. %By reliably enlarging the limit of the spin and orbital sum rules, which usually holds for materials where the magnetic ions exhibit a unique crystal field symmetry This finding translates in a sign-reversal between the average Fe magnetic orbital and spin moments. Large Fe-displacements, among some of the octahedral sites, lower the symmetry of the system producing anisotropic paths for the Fe-O bondings giving rise to a large orbital-lattice interaction akin to a preferential crystallographic direction for the magnetic orbital moment. The latter may lead to a partial re-orientation of the magnetic orbital moment under an external magnetic field that, combined to the ferrimagnetic nature of the GFO, can qualitatively explain the observed sign-reversal of the XMCD integral. The results suggest that a control over the local symmetry of the oxygen octahedra in transition metal oxides can offer a suitable leverage over the manipulation of the effective orbital and spin moments in magnetoelectric systems.

Self-biased magnetoelectric switching at room temperature in three-phase ferroelectric–antiferromagnetic–ferrimagnetic nanocomposites

Magnetoelectric systems could be used to develop magnetoelectric random access memory and microsensor devices. One promising system is the two-phase 3-1-type multiferroic nanocomposite in which a one-dimensional magnetic column is embedded in a three-dimensional ferroelectric matrix. However, it suffers from a number of limitations including unwanted leakage currents and the need for biasing with a magnetic field. Here we show that the addition of an antiferromagnet to a 3-1-type multiferroic nanocomposite can lead to a large, self-biased magnetoelectric effect at room temperature. Our three-phase system is composed of a ferroelectric Na0.5Bi0.5TiO3 matrix in which ferrimagnetic NiFe2O4 nanocolumns coated with antiferromagnetic p-type NiO are embedded. This system, which is self-assembled, exhibits a magnetoelectric coefficient of up to 1.38 × 10–9 s m–1, which is large enough to switch the magnetic anisotropy from the easy axis (Keff = 0.91 × 104 J m–3) to the easy plane (Keff = –1.65 × 104 J m–3). A three-phase system that is composed of a ferroelectric Na0.5Bi0.5TiO3 matrix in which ferrimagnetic NiFe2O4 nanocolumns coated with antiferromagnetic p-type NiO are embedded exhibits self-biased magnetoelectric switching at room temperature.

FEATURES AND PRINCIPLES OF THE DEVELOPMENT OF BRUSHLESS MAGNETOELECTRIC SYSTEMS OF THE RETURN-ROTARY MOTION

The paper reviews the results of studies of brushless magnetoelectric systems of return-rotary motion, carried out for many years at the Electrodynamics Institute of the National Academy of Sciences of Ukraine. Structures of specialized brushless magnetoelectric motors with elastic magnetic coupling between the stator and the rotor are presented. An example of structural optimization of the motor is given. The electromechanical characteristics of the motors of the return-rotary motion are described and the indexes of their efficiency are proposed. An example of the formation of functional dependences for motor control in an open-loop system is given. Structures of the system for automatic control of the rotor oscillations angle amplitude and stator current limitation, as well as a system for vector control of the auxiliary winding current for active compensation of reactive alternating torque of the main rotor are presented. Examples of calculation of transient responses of the main parameters of the motor are given. Reference 11, figure 9.

Magnetoelectric materials and devices

Over the past few decades, magnetoelectric (ME) materials and devices have been investigated extensively, which is one of the most interesting research topics since the revival of multiferroic laminates with large ME coupling coefficients. The existence of two or more ferroic properties in the ME systems plays key roles in the next generation of novel multifunctional devices. Strong ME coupling has been demonstrated in various ME systems, including single-phase bulk or thin-film materials and bulk or thin-film composites such as piezoelectric/magnetostrictive heterostructures. Based on the coupling mechanisms, a variety of device applications have attracted ever-increasing attention, such as magnetic field sensors, voltage tunable inductors, mechanical ME antennas, which are compact, lightweight, and power-efficient. These novel ME materials and devices provide great opportunities for next-generation magnetic field sensing, communication systems, spintronics, nonvolatile memory applications, etc. In this paper, we try to summarize the most recent progress on ME materials, phenomena, and devices in the past few years, with emphasis on thin-film composite materials and devices. Some unsolved questions and future directions where the community could head for are also provided.

Nickel ferrite embedded polyvinylidene fluoride composite based flexible magneto-electric systems

Developing flexible multiferroic composite with magnetoelectric coupling is highly desirable for the wearable electronic devices, magnetic field sensors, actuators, energy harvesters and memory devices. Here, a flexible artificial multiferroic composite was fabricated using ferromagnetic nickel ferrite (NiFe2O4) nanoparticles (NPs) as filler in the ferroelectric polyvinylidene fluoride (PVDF) matrix. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies revealed the formation of the inverse spinel phase in NiFe2O4 NPs. The vibrating sample magnetometer (VSM) and XRD measurements showed an increase in the magnetic moment and the electroactive β phase fraction, respectively, in PVDF/NiFe2O4 composite with the increasing loading concentration of NiFe2O4 filler NPs. With the increase in NiFe2O4 NPs loading concentration to 40 wt % the magnetoelectric coupling between the ferroelectric (PVDF) and ferromagnetic (NiFe2O4 NPs) was confirmed using magnetocapacitance measurement. This work successfully demonstrates the potential of artificial multiferroic PVDF/NiFe2O4 composite system, with enhanced dielectric property and room temperature magnetoelectric coupling, for future flexible electronic devices.

Flexible Out-of-Plane Wind Sensors with a Self-Powered Feature Inspired by Fine Hairs of the Spider.

The quest for out-of-plane and self-powered wind sensors has motivated the field of outdoor sports, exploration, space perception, and positioning. Fine hairs of spiders act as hundreds of individual wind sensors, allowing them to feel the nearby wind change caused by the predators or the prey. Inspired by this natural teacher, here, we demonstrate the fabrication of bioinspired self-powered out-of-plane wind sensors based on flexible magnetoelectric material systems. The shape of flexible sensors, by patterning silver nanoparticles on a thin polyethylene terephthalate film through a screen printing technique, mimics fine hairs of the spiders, allowing for out-of-plane tactile perceptual monitoring caused by the wind. Owing to the employment of flexible magnetoelectric materials, the sensors can distinguish forward/backward winds and are totally self-powered. The working mechanism for sensors has been explained by the Maxwell numerical simulation, allowing for further improvement of their performance by tuning diverse factors. Furthermore, the wind sensor can detect the wind with a velocity down to 1.2 m/s and distinguish multidegree wind by their arrays. It is expected that, in the near future, our design can provide new findings for out-of-plane wind sensors with superior self-powered properties toward new flexible electronics.

Effect of CoFe2O4 weight fraction on multiferroic and magnetoelectric properties of (1 − x)Ba0.85Ca0.15Zr0.1Ti0.9O3 − xCoFe2O4 particulate composites

Different compositions of the composite lead-free multiferroic magnetoelectric systems are fabricated by employing piezoelectric Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) and magnetostrictive CoFe2O4 (CFO) by varying the CFO weight fraction. The magnetic, dielectric, ferroelectric and magnetoelectric (ME) properties of the system are analyzed and found to be varying with the ferrite concentration. Even though the composite systems exhibit high magnetocapacitance (MC) properties (~ 35%), the possible stray contributions from magnetoresistance and magnetostriction make it unreliable for the quantitative determination of ME coupling coefficient (MECC). Therefore, a dynamic method is chosen for the measurement of magnetoelectric coupling. All the compositions have shown fairly good ME coupling. It is found that the ME coupling increases with ferrite fraction and the highest ME coupling of 14.8 mV/(cm Oe) is observed for 0.6BCZT–0.4CFO composite. It is also observed that the ME voltage increases linearly with the ac modulating field with a voltage generation of 1.25 V/cm (for x = 0.4) for a small ac modulating field of 100 Oe. This high sensitivity and linear response of ME coupling to the ac magnetic fields offer the possibility of employing these particulate composites for a wide range of applications from magnetic field sensors to energy harvesters.