Magnetoelectric Microwave Devices Research Articles

Shear-strain-mediated large nonvolatile tuning of ferromagnetic resonance by an electric field in multiferroic heterostructures

Controlling magnetism by an electric field is of critical importance for the future development of ultralow-power electronic and spintronic devices. Progress has been made in electrically driven nonvolatile tuning of magnetic states in multiferroic heterostructures for the information storage industry, which is exclusively attributed to the ferroelectric-polarization-switching-induced interfacial charge effect or nonlinear lattice strain effect. Here, we demonstrate that a hitherto unappreciated shear strain in the ferroelectric 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 substrate triggered by an electric field can be adopted to obtain robust nonvolatile control of the ferromagnetic resonance in an elastically coupled epitaxial Fe70Rh30 thin film. The disappearance of the resonance peak in a low-field-sweeping mode and the large resonance field shift of 111 Oe upon polarization switching demonstrate a strong shear-strain-mediated magnetoelectric coupling effect. In particular, in situ Kerr measurement identifies that the nonvolatile magnetic switching purely originates from electric-field-induced 109° ferroelastic domain switching rather than from 71°/180° ferroelectric domain switching even without the assistance of a magnetic field. This discovery illustrates the role of shear strain in achieving electrically tunable nonvolatile modulation of dynamic magnetic properties, and favors the design of future energy-efficient magnetoelectric microwave devices.

Studies on mechanical loss in converse magnetoelectric effect under multi-physical field

By means of the technic for measuring resonant converse magnetoelectric (CME) effect, the mechanical loss of PZT/Terfenol-D/PZT tri-layer symmetric magnetoelectric laminated composites under multi-physical field loads such as bias magnetic field, driven voltage and ambient temperature is systematically measured in this paper. The experimental results show that the mechanical loss in CME effect increases initially with the increase of the bias magnetic field, and approaches to a broad maximum value at 250–500 Oe. Further increasing bias magnetic field leads to the decrease of mechanical loss. The mechanical loss increases rapidly with the increase of driven voltage amplitude, especially in the medium magnitude of the bias magnetic field. While, there is little influence of voltage on the mechanical loss under the higher bias magnetic fields. Importantly, the mechanical loss increases monotonically as the increase of ambient temperature. The research results of the mechanical loss under multi-physics fields in this paper can provide a basic principle of CME improvement by reducing the mechanical loss. Therefore, this research is quite significant to the CME based applications, such as, magnetoelectric transducers, magnetoelectric microwave devices, multiferroic antennas and so on.

Modeling of magnetoelectric microwave devices

The possibility of computer modeling implementation of electrically controlled magnetoelectric (ME) microwave devices is considered. The computer modeling results of different structures of ME microwave devices based on layered ferrite-piezoelectric structure formed on the slot line, microstrip line and coplanar waveguide are offered. Results are reported as frequency dependencies of insertion losses of ME devices.

Electric field modulation of ultra-high resonance frequency in obliquely deposited [Pb(Mg1/3Nb2/3)O3]0.68-[PbTiO3]0.32(011)/FeCoZr heterostructure for reconfigurable magnetoelectric microwave devices

The multiferroic heterostructure of FeCoZr/[Pb(Mg1/3Nb2/3)O3]0.68-[PbTiO3]0.32(011) (PMN-PT) prepared by oblique sputtering deposition technique shows a large electrical tunability of ultra-high ferromagnetic resonance frequency from 7.4 GHz to 12.3 GHz. Moreover, we experimentally demonstrate the possibility of realizing electrically reconfigurable magnetoelectric microwave devices with ultra-low power consumption by employing the heterostructure under different resetting electric fields through a reconfiguration process. In particular, the tunability of the FeCoZr/PMN-PT heterostructure from 8.2 GHz to 11.6 GHz can retain in a remanent state after releasing the resetting electric field. This suggests that the tunable microwave devices based on such heterostructures are permanently reconfigurable by simply using a trigger electric field double-pulse which requires much less energy than that of the conventional ones wherein an electric field needs to be constantly applied during operation.

A generalized lumped-element equivalent circuit for tunable magnetoelectric microwave devices with multi-magnetoelectric laminates

According to the microwave transmission principle and the mechanism of ferromagnetic resonance, a generalized lumped element model for electrically and magnetically magnetoelectric tunable microwave devices with multi-magnetoelectric laminates is established. This model is introduced the RLC series resonant circuit and an ideal transformer model to characterize the ferromagnetic resonance effect and the coupling between microstrip line and the magnetoelectric laminates. Then, the model is degenerated to an existing microwave resonator, which contains only a single block magnetoelectric laminate, and transmission characteristics results predicted by the lumped element model are compared with the experimental results and the electromagnetic simulated results. It is found that the lumped circuit model can effectively predict the center frequency and bandwidth of the resonator. After that, the lumped element model is used to predict the band characteristics and the magnetic and electric tunability of the filter with multi-magnetoelectric laminates. The results show that the application of multi-magnetoelectric laminates in filters can not only broaden bandwidth, but also control the work frequency band by tuning the external electrostatic and magnetostatic field on the magnetoelectric laminates. Therefore, considering the practicality and versatility of microwave devices with multi-magnetoelectric laminates, the effective lumped element model can provide the theoretical basis for the design of novel magnetoelectric devices.

Voltage‐Impulse‐Induced Non‐Volatile Ferroelastic Switching of Ferromagnetic Resonance for Reconfigurable Magnetoelectric Microwave Devices

A critical challenge in realizing magnetoelectrics based on reconfigurable microwave devices, which is the ability to switch between distinct ferromagnetic resonances (FMR) in a stable, reversible and energy efficient manner, has been addressed. In particular, a voltage-impulse-induced two-step ferroelastic switching pathway can be used to in situ manipulate the magnetic anisotropy and enable non-volatile FMR tuning in FeCoB/PMN-PT (011) multiferroic heterostructures.

Ferromagnetic resonance properties of Fe81−xNixGa19/Si(1 0 0) and Fe81−yNiyGa19/glass films

Two series of Fe81−xNixGa19/Si(100) and Fe81−yNiyGa19/glass films, where x or y=0–26, were made by the magnetron sputtering method. The film thickness (tf) was fixed at 100nm. We have performed three kinds of experiments on these films: (i) the saturation magnetostriction (λS) measurement; (ii) the easy-axis and hard-axis magnetic hysteresis loop measurements; and (iii) the ferromagnetic resonance (FMR) experiment to find the resonance field (HR) with an X-band cavity tuned at fR=9.6GHz. The natural resonance frequency, fFMR, of the Kittel mode at zero external field (H=0) is defined as fFMR≒ν[HK4πMS]1/2, where γ=2πν is the gyromagnetic ratio, HK and 4πMS are the uniaxial anisotropy field and saturation magnetization, and HK<<4πMS. The Gilbert damping constant, α, is calculated from the formula, α=[ν(ΔH)S]/(2fR), where (ΔH)exp=(ΔH)S+(ΔH)A, (ΔH)exp is the half-width of the absorption peak around the resonance field HR, (ΔH)S is the symmetric part of (ΔH)exp, and (ΔH)A is the asymmetric part. The degree of asymmetry, (ΔH)A/(ΔH)exp, is associated with the structural and/or magnetic inhomogeneities in the film. The main findings of this study are as follows: (A) fFMR tends to decrease, as x or y increases; (B) α decreases from 0.052 to 0.020 and then increases from 0.020 to 0.050, as x increases, and α decreases from 0.060 to 0.013 in general, as y increases; and (C) λS reaches a local maximum when x=22. We conclude that the Fe59Ni22Ga19/glass film should be the most suitable for application in magneto-electric microwave devices.

Ultra-low power electrically reconfigurable magnetoelectric microwave devices

We present an electrical tunable spiral inductor design and simulation results. By integrating (011) oriented single crystal ferroelectric substrate [Pb(Mg1/3Nb2/3)O3](1−x)-[PbTiO3]x (PMN-PT, x ≈ 0.32) with tunable and switchable remanent strain property, the tunability of such magnetoelectric microwave inductor can retain after releasing the electric actuation, i.e., electrically reconfigurable. A series of reconfigurable passive magnetoelectric microwave devices based on this concept are proposed and discussed. Those electrically reconfigurable magnetoelectric microwave devices have the advantage of low power consumption and fast and wide tunability, which can be potentially used for many applications.

The Electric Field Tuning Characteristics in the Strain-Mediated Ferrite-Piezoelectric Laminated Magnetoelectric Microwave Devices

This research focused on the numerical simulation of electric field tuning characteristics of the magnetoelectric microwave devices with the core of the laminated ferrite-piezoelectric magnetoelectric materials. Firstly, we proposed an expression for the shift of ferromagnetic resonance (FMR) frequency tuning by external electric field in piezoelectric layer, then substituted the expression of magnetoelectic (ME) constant into this expression, which can convert the electric field tuning on the laminated magnetoelectric materials into the equivalent magnetic field tuning on the ferrite layer. Secondly, we built a numerical analysis model for tunable magnetoelectric microwave device which is formed by the laminated magnetoelectric material and microstrip line, and put the equivalent magnetic field into this numerical model, then the numerical analysis model of novel tunable magentoelectric microwave device is completed. Taking a tunable ME microwave resonator for example, the S parameters calculated by the numerical model in this paper are in good agreement with experimental results both qualitatively and quantitatively. Considering the demand for the designing and applying of the microwave devices, we studied the effect of geometrical dimensions of the ferrite layer (YIG/GGG) on the return loss and the resonance frequency.

Soft magnetism, magnetostriction, and microwave properties of FeGaB thin films

A series of (Fe100−yGay)1−xBx (x=0–21 and y=9–17) films were deposited; their microstructure, soft magnetism, magnetostrictive behavior, and microwave properties were investigated. The addition of B changes the FeGaB films from polycrystalline to amorphous phase and leads to excellent magnetic softness with coercivity &amp;lt;1Oe, high 4πMs, self-biased ferromagnetic resonance (FMR) frequency of 1.85GHz, narrow FMR linewidth (X band) of 16–20Oe, and a high saturation magnetostriction constant of 70ppm. The combination of these properties makes the FeGaB films potential candidates for tunable magnetoelectric microwave devices and other rf/microwave magnetic device applications.

Magnetoelectric microwave phase shifters

We discuss magnetoelectric microwave devices. Combination of properties of ferrite and ferroelectric, and also the properties, induced by magnetoelectric (ME) interaction, find wide functional opportunities for creation of devices on the basis of ME materials. ME materials can be used for design of microwave phase shifters. Phase shifters will be most simply realised on effect of shift of a line of ferromagnetic resonance (FMR) under the action of a control electrical field. We shall consider an example of ME microwave through-passage microstrip phase shifter. As a working element a composite material, consisting of 95% from yttrium-iron garnet and of 5% from piezoceramics PZT is used. Phase shifters on ME materials have high performance, adaptability to manufacture, electromagnetic compatibility, radiating durability, thermostability, low power in control circuit.