Magnetostrictive Coupling Research Articles

A Piezotronic and Magnetic Dual‐Gated Ferroelectric Semiconductor Transistor

AbstractPiezotronics is the coupling effect of the piezoelectric and semiconductor properties; however, the piezoelectric constant of the piezoelectric semiconductor is relatively small while the ferroelectric materials with large piezoelectric constant typically possess weak semiconductor properties, thus limiting the effective coupling coefficient of the piezotronic materials and devices. Here, a piezotronics and magnetic dual‐gated ferroelectric semiconductor transistor (PM‐FEST) is fabricated by Terfenol‐D, aluminum oxide (Al2O3), and ferroelectric semiconductor α‐In2Se3, which has a large piezoelectric coefficient, room‐temperature ferroelectricity, and dipole locking. The charge carrier transport and corresponding drain current of the PM‐FEST can be directly modulated by either the applied magnetic field or external strain. At a low magnetic field (<200 mT), the maximum current on/off ratio of α‐In2Se3 based PM‐FEST is as high as 1700%. Compared with traditional piezotronic devices, the PM‐FEST demonstrates a higher gauge factor (2.3 × 104) than that of the piezoelectric semiconductors. This work provides a possibility of realizing magnetism‐modulated electronics in semiconductors by exploiting the coupling of piezotronics and magnetostriction.

Thermo-Magnetostrictive Effect for Driving Antiferromagnetic Two-Dimensional Material Resonators.

Magnetostrictive coupling has recently attracted interest as a sensitive method for studying magnetism in two-dimensional (2D) materials by mechanical means. However, its application in high-frequency magnetic actuators and transducers requires rapid modulation of the magnetic order, which is difficult to achieve with external magnets, especially when dealing with antiferromagnets. Here, we optothermally modulate the magnetization in antiferromagnetic 2D material membranes of metal phosphor trisulfides (MPS3), to induce a large high-frequency magnetostrictive driving force. From the analysis of the temperature-dependent resonance amplitude, we provide evidence that the force is due to a thermo-magnetostrictive effect, which significantly increases near the Neél temperature, due to the strong temperature dependence of the magnetization. By studying its angle dependence, we find the effect is observed to follow anisotropic magnetostriction of the crystal lattice. The results show that the thermo-magnetostrictive effect results in a strongly enhanced thermal expansion force near the critical temperature of magnetostrictive 2D materials, which can enable more efficient actuation of nano-magnetomechanical devices and can also provide a route for studying the high-frequency coupling among magnetic, mechanical, and thermodynamic degrees of freedom down to the 2D limit.

Light-Controlled Magnetoelastic Effects in Ni/BaTiO3 Heterostructures

Magnetoelastic and magnetoelectric coupling in the artificial multiferroic heterostructures facilitate valuable features for device applications such as magnetic field sensors and electric-write magnetic-read memory devices. In ferromagnetic/ferroelectric heterostructures, the intertwined physical properties can be manipulated by an external perturbation, such as an electric field, temperature, or a magnetic field. Here, we demonstrate the remote-controlled tunability of these effects under visible, coherent, and polarized light. The combined surface and bulk magnetic study of domain-correlated Ni/BaTiO3 heterostructures reveals that the system shows strong sensitivity to the light illumination via the combined effect of piezoelectricity, ferroelectric polarization, spin imbalance, magnetostriction, and magnetoelectric coupling. A well-defined ferroelastic domain structure is fully transferred from a ferroelectric substrate to the magnetostrictive layer via interface strain transfer. The visible light illumination is used to manipulate the original ferromagnetic microstructure by the light-induced domain wall motion in ferroelectric substrates and consequently the domain wall motion in the ferromagnetic layer. Our findings mimic the attractive remote-controlled ferroelectric random-access memory write and magnetic random-access memory read application scenarios, hence facilitating a perspective for room temperature spintronic device applications.

A High-Sensitivity Resonant Magnetic Sensor Based on Graphene Nanomechanical Resonator.

This paper presents a novel resonant magnetic sensor consisting of a graphene nanomechanical oscillator and magnetostrictive stress coupling structure, using Si/SiO2 substrate and Fe–Ga alloy, respectively. In this device, the deformation of the Fe–Ga alloy resulting from the external magnetic field changed the surface tension of the graphene, resulting in a significant change in the resonance frequency of graphene. Using the finite element analysis, it could be found that the response of the resonance frequency revealed a good linear relationship with the external magnetic field (along the x-axis) in the range of the 1 to 1.6 mT. By optimizing the sizes of each component of the magnetic sensor, such as the thickness of the Si/SiO2 substrate and the Fe–Ga alloy, and the length of the graphene, the sensitivity could even reach 834 kHz/mT, which is three orders of magnitude higher than conventional resonant magnetic devices. This provides a new method for highly sensitive and miniaturized magnetic sensors.

A Longitudinal Mode Guided Wave Transducer With the Ring Permanent Biased Magnet Based on Magnetostrictive Effect for Large Diameter Bridge Cables

The existing yoke magnetizers can be used for large diameter bridge cable detection, but cannot provide the optimal bias magnetic field due to the repulsion of the polarities arranged in the circumferential direction, which reduces the energy conversion efficiency of the magnetostrictive longitudinal mode guided wave transducer. A magnetostrictive longitudinal mode guided wave transducer with the ring permanent biased magnet is provided to improve energy conversion efficiency for large diameter bridge cables. Firstly, a ring magnetizer for the axial magnetization is proposed, which inspired by the structure of the yoke magnetizer and the adjustable bias magnetic field generated by the solenoid coil. Then, the specific transducer with the ring magnetizers is designed for PES(C) 7-127 cable. Based on the magnetostrictive coupling coefficient curves and magnetization curve of the cable steel wire, the finite element models verify that the magnetization effect of the ring magnetizer is better than the yoke magnetizer for PES(C) 7-127 cables. Furthermore, the structural parameters of the ring magnetizers are optimized based on magnetization strength and magnetization uniformity. Finally, the improved efficiency of the transducer is verified by experiments. The energy conversion efficiency of the transducer is increased by 43.65% at the transmitting side, 4.76% at the receiving side, 48.41% at the both sides. Besides, the weight of the ring magnetizers is 19.85% lower than the yoke magnetizers.

Linear and nonlinear optical responses in Kitaev spin liquids

We theoretically study THz-light-driven high-harmonic generation (HHG) in the spin-liquid states of the Kitaev honeycomb model with a magnetostriction coupling between spin and electric polarization. To compute the HHG spectra, we numerically solve the Lindblad equation, taking account of the dissipation effect. We find that isotropic Kitaev models possess a dynamical symmetry, which is broken by a static electric field, analogous to HHG in electron systems. We show that the HHG spectra exhibit characteristic continua of Majorana fermion excitations, and their broad peaks can be controlled by applying static electric or magnetic fields. In particular, the magnetic-field dependence of the HHG spectra drastically differs from those of usual ordered magnets. These results indicate that an intense THz laser provides a powerful tool to observe dynamic features of quantum spin liquids.

Mode-sensitive magnetoelastic coupling in phononic-crystal magnomechanics

The acoustically driven spin-wave resonance in a phononic-crystal cavity is numerically investigated. The designed cavity enables confinement of gigahertz vibrations in a wavelength-scale point-defect structure and sustains a variety of resonance modes. Inhomogeneous strain distributions in the modes modify the magnetostrictive coupling and the spin-wave excitation susceptible to an external-field orientation. In particular, a monopole-like mode in the cavity having a near-symmetrical pattern shows a subwavelength-scale mode volume and can provide a versatile acoustic excitation scheme independent of the field-angle variation. Thus, the phononic-crystal platform offers an alternative approach to acoustically control the spin-wave dynamics with ultrasmall and inhomogeneous mode structures, which will be a key technology to integrate and operate large-scale magnomechanical circuits.

Signatures of magnetostriction and spin-phonon coupling in magnetoelectric hexagonal15R−BaMnO3

Spin-phonon coupling, the interaction of spins with surrounding lattice is a key parameter to understand the underlying physics of multiferroics and engineer their magnetization dynamics. Elementary excitations in multiferroic materials are strongly influenced by spin-phonon interaction, making Raman spectroscopy a unique tool to probe these coupling(s). Recently, it has been suggested that the dielectric and magnetic properties of 15R-type hexagonal BaMnO3 are correlated through the spin-lattice coupling. Here, we report the observation of an extensive renormalization of the Raman spectrum of 15R-BaMnO3 at 230 K, 280 K, and 330 K. Magnetic measurements reveal the presence of a long-range and a short-range magnetic ordering in 15R-BaMnO3 at 230 K and 330 K, respectively. The Raman spectrum shows the appearance of new Raman modes in the magnetically ordered phases. Furthermore, an additional Raman phonon appears below ~ 280 K, possibly arising from a local lattice-distortion due to the displacement of Mn-ions, that exhibits anomalous shift with temperature. The origin of the observed renormalization and phonon anomalies in Raman spectra are discussed based on the evidences from temperature- and magnetic-field-dependent Raman spectra, temperature-dependent x-ray diffraction, magnetization, and specific heat measurements. Our results indicate the presence of magnetostriction and spin-phonon coupling in 15R-BaMnO3 thus suggesting that the optical phonons are strongly correlated to its magnetoelectric properties.

Mechanism of Controllable Force Generated by Coupling Inverse Effect of Piezoelectricity and Magnetostriction

A method based on piezoelectric and magnetostrictive coupling inverse effect to generate precise controllable force is proposed to meet the requirement of manipulation force control in ultra-precision machining and assembly process. According to the principle of magnetic flux continuity, combine with the characteristics of piezoelectric and magnetostrictive inverse effects, the working mechanism of force generation is analyzed, and the theoretical model of the relationship between output force and parameters which include material characteristics, geometric parameters, working voltage of piezoelectric ceramics is established. An experimental device consisting of piezoelectric ceramic driving power supply, strain gauge, static strain tester, micro laser displacement sensor, force sensor, data acquisition card and magnetic force control component is developed. The relationship between output magnetic force and air gap or working voltage are studied by experiment and simulation. The results show that the output force variations of simulation and experiment are close. The output magnetic force fluctuation is small and with good stability. It verifies the consistency and correctness of the theoretical, simulation and experimental results.

The PZT/Ni unimorph magnetoelectric energy harvester for wireless sensing applications

The PZT/Ni unimorph cantilever with permanent Nd-magnet (NdFeB) as a tip mass is proposed for harvesting energy from the low frequency (50/60 Hz) and low amplitude magnetic field (≤10 Oe) for wireless sensing applications. The maximum power density of PZT/Ni unimorph cantilever is 270 µW/cm3 at a resonant frequency of 50 Hz (1 Oe), being one order of magnitude higher than a previously reported PZT/Cu cantilever energy harvester (11.73 μW/cm3), and comparable to an expensive PMN-PZT single crystal fiber/multi-layer FBS film cantilever energy harvester (333 μW/cm3). The acquired output power allows the energy harvester to turn on 100 commercial LEDs without a power storage unit. Both experiments and finite element analysis imply that the enhanced power density is due to the coupling of magnetostriction of the Ni beam and magnetic torque of the Nd-magnet. Together with a simple electric circuit, the PZT/Ni unimorph cantilever can successfully power a commercial wireless temperature/humidity sensor. The proposed ME energy harvester was demonstrated to scavenge ambient magnetic energy and a power wireless sensing system, exhibiting great potential for application in the IoT (internet of things).

Effect of Tensile Force on Magnetostrictive Sensors for Generating and Receiving Longitudinal Mode Guided Waves in Steel Wires

When the longitudinal mode guided waves based on magnetostrictive effect were employed to inspect the bridge cables, we found that there was a large difference in the signal’s amplitude of the same specification cable under different tensile force. This difference would affect the test results and the identification of defects. It is necessary to study the effect of tensile force on the signal for the reliability of detection. Firstly, the effective field theory is employed to take the force as an additional bias magnetic field. Then, the effect of the tensile force on generating and receiving longitudinal mode guided waves based on magnetostrictive effect is obtained by the relationship between the bias magnetic field and the magnetostrictive coupling coefficient. Finally, the experiment of the magnetostrictive sensor is carried out on a Φ5 mm steel wire under different force. The experimental results are in good agreement with the theoretical results. The results show that the existence of the tensile force would change the operation point for generating and receiving the longitudinal mode guided waves based on magnetostrictive effect, which associated with the coupling coefficient. In order to obtain the optimal conversion efficiency for the force state wire and cable, the applied bias magnetic field should be set smaller than the bias magnetic field for the force-free state.

Characterization of magnetomechanical properties in FeGaB thin films

Layered magnetic/piezoelectric heterostructures have drawn a great amount of interest for their potential use in ultra-sensitive magnetoelectric (ME) sensors, ME antennas, voltage tunable inductors, magnetic tunable resonators, etc. It is critically important to characterize the saturation magnetostriction, piezomagnetic coefficient, ΔE effect, and magnetomechanical coupling factor of magnetic thin films, which determine the performance of these ME devices. In this work, a sensitive system has been developed to measure these magnetomechanical properties, on which several different magnetostrictive thin films on the silicon substrate cantilever were characterized. A 0.015 ppm limit of detection of the magnetostriction tester and a frequency resolution of 0.01 Hz of the ΔE tester have been achieved. After magnetic anneal treatment, a record high piezomagnetic coefficient of 12 ppm/Oe, a giant magnetic field induced Young's modulus change of 153 GPa, and a high effective magnetomechanical coupling factor of 0.84 have been measured in FeGaB thin films.

Coupling magneto-elastic Lagrangians to spin transfer torque sources

The consequences of coupling magnetic and elastic degrees of freedom, where spins and deformations are carried by point-like objects subject to local interactions, are studied, theoretically and by detailed numerical simulations. From the constrained Lagrangians we derive consistent equations of motion for the coupled dynamical variables. In order to probe the dynamics of such a system, we consider external perturbations, such as spin transfer torques for the magnetic part, and homogeneous stresses for the elastic part, associated to their corresponding damping. This approach is applied to the study of ultrafast switching processes in anti-ferromagnetic systems, which have recently attracted attention as candidates for anti-ferromagnetic spintronic devices. Our strategy is then checked in simple, but instructive, situations. We carried out numerical experiments to study, in particular, how the magnetostrictive coupling and external stresses affect the nature of the switching processes in a prototype anti-ferromagnetic material.

Theory of magnetoelectric effects in multiferroic core–shell nanofibers of hexagonal ferrites and ferroelectrics

A model is developed for magnetoelectric (ME) interactions in coaxial nanofibers of hexagonal ferrites and ferroelectrics. Multiferroic nanocomposites with hexagonal ferrites are of interest for achieving strong ME coupling under zero external magnetic bias due to their high uniaxial or planar anisotropy fields. In this work we considered the ME coupling in core–shell fibers of lead zirconate titanate (PZT) and ferrimagnetic W- and Y-type hexagonal ferrites with high magnetostriction and piezomagnetic coupling. Modeling of the direct-ME effects, i.e. sample response to an applied magnetic field, is done in terms of the ME voltage coefficients (MEVCs) at low frequencies and at electromechanical resonance (EMR). The converse-ME effect, response of the fibers to an applied DC electric field, is considered at ferromagnetic resonance (FMR). Expressions have been obtained for MEVCs at low frequency and EMR, and for the converse-ME coefficient at FMR. The theory predicts strongest direct-ME coupling in fibers of Ni2Y-PZT and the weakest coupling in Zn2Y-PZT. The MEVC at EMR is one to two orders of magnitude higher than at low frequency and the peak MEVC remains the same for fibers of ferrite core-PZT shell as for PZT core-ferrite shell. The converse-ME effect is expected to be the strongest for fibers of Co2W-PZT and weakest in Ni2Y-PZT. The model has been extended to include an assembled array of core–shell fibers and weakening of the ME coupling is predicted in such arrays due to magnetic and electric dipole–dipole interactions. The theory presented here is of importance for self-biased sensors of low frequency and RF magnetic fields.

Rotomagnetic coupling in fine-grained multiferroic BiFeO3 : Theory and experiment

Using Landau-Ginzburg-Devonshire (LGD) theory for BiFeO3 dense fine grained ceramics with quasi spherical grains and nanosized inter grain spaces enriched by elastic defects, we calculated a surprisingly strong size-induced increase of the AFM temperature caused by the joint action of rotomagnetic and magnetostrictive coupling. Notably that all parameters included in the LGD functional have been extracted from experiments, not assumed. Complementary we performed experiments for dense BiFeO3 ceramics, which revealed that the shift of antiferromagnetic transition to 690 K instead of 645 K for a single crystal. To explain theoretically the result, we consider the possibility to control antiferromagnetic state of multiferroic BiFeO3 via biquadratic antiferrodistortive rotomagnetic, rotoelectric, magnetostrictive and magnetoelectric couplings. According to our calculations the highest is the rotostriction contribution, the magnetostrictive and electrostriction contributions appeared smaller.

Thermal Vibration of Laminated Magnetostrictive Plates Without Shear Effects

The study of laminated magnetostrictive plate without shear deformation under thermal vibration is calculated by using the generalized differential quadrature (GDQ) method. In the thermoelastic stress-strain relations that containing the linear temperature rise and the magnetostrictive coupling terms with velocity feedback control. The dynamic differential equations without shear deformation are normalized and discrete into the dynamic discretized equations with GDQ method. Four edges of rectangular laminated magnetostrictive plate with simply supported boundary conditions are considered. In the moderately thick plate of laminated magnetostrictive plate, the effect of shear deformation should be considered for the computational controlled values of transverse center deflection and dominated normal stress.

Suitability of cation substituted cobalt ferrite materials for magnetoelastic sensor applications

The results of a study on the suitability of materials derived from cobalt ferrite for sensor and actuator applications are presented. The mechanism responsible for the superior sensor properties of Ge-substituted cobalt ferrite compared with Ti and other cation substituted cobalt ferrite materials is believed to be due to the tetrahedral site preference of Ge4+ and its co-substitution with Co2+. Results also showed that the higher strain derivative of Ge-substituted cobalt ferrite compared with Ti-substitution is due to a higher magnetostrictive coupling in response to applied field in the material.

Theoretical study on the role of dynamics on the unusual magnetic properties in MnBi.

We study the electronic structure and lattice dynamics in the ferromagnet MnBi using first-principles calculations and a tight-binding model. The band structure around the Fermi level is dominated by Bi-p states which are the primary contributors to the magnetic anisotropy energy in the low temperature structure. A tight-binding model consisting of Mn-d and Bi-p states is developed and the parameters are determined from first-principles calculations. Phonon dispersions and elastic moduli exhibit several interesting features. The results imply that the magnetic interaction with the crystal lattice in MnBi is considerably more complex than previously thought and in particular that there is a rich interplay between phonons and magnetism involving both magnetoelastic and magnetostrictive coupling.

Numerical simulation of guided waves using equivalent source model of magnetostrictive patch transducers

While magnetostrictive patch transducers have become more widely used for damage inspection of waveguides such as plates or pipes, the numerical simulation of guided waves excited by the transducers is very limited. Recently, one-way, coupled time-harmonic, finite element analysis based on the linearized magnetostrictive coupling equation has been conducted, but transient analysis must be carried out to extract more information including the reflected waves from cracks. Naturally, fully coupled or one-way coupled multiphysics transient finite element analysis would require substantial computational resources and cost. In order to utilize an efficient structural finite element method or code, we newly propose equivalent distributed force models that can describe the actuation mechanism of the magnetostrictive patch transducer without explicitly solving coupled multiphysics equations. Once equivalent force models are established, transient wave simulations in inspected waveguides can be accomplished efficiently through any structural finite element code. The essence of this approach is to establish the equivalent actuating force models useful for various types of magnetostrictive patch transducers currently available. The validity of the developed models is checked by investigating the wave radiation patterns of the Rayleigh–Lamb and shear–horizontal waves in test waveguides, and the simulated results obtained with the proposed models are compared against the available experimental results.

Surface-acoustic-wave-driven ferromagnetic resonance in (Ga,Mn)(As,P) epilayers

Interdigitated transducers were used to generate and detect surface acoustic waves on a thin layer of (Ga,Mn)(As,P). The out-of-plane uniaxial magnetic anisotropy of this dilute magnetic semiconductor is very sensitive to the strain of the layer, making it an ideal test material for the dynamic control of magnetization via magneto-striction. The time-domain measurement of the amplitude and phase of the transmitted SAW during magnetic field sweeps indicated a clear resonant behavior at a field close to the one calculated to give a precession frequency equal to the SAW frequency. A resonance was observed from 5K to 85K, just below the Curie temperature of the layer. A full analytical treatment of the coupled magnetization/acoustic dynamics showed that the magneto-strictive coupling modifies the elastic constants of the material and accordingly the wave-vector solution to the elastic wave equation. The shape and position of the resonance were well reproduced by the calculations, in particular the fact that velocity (phase) variations resonated at lower fields than the acoustic attenuation variations.