Magnetoelectric Gyrator Research Articles

Магнитоэлектрический гиратор на основе трехслойных симметричных структур: теория и эксперимент

The work is devoted theoretical and experimental studies of a magnetoelectric gyrator, consisting of an inductor coil, inside which there is a magnetoelectric heterostructure, which is a mechanically connected piezoelectric layer and two magnetic layers. Using the system of equations of elasto- and electrodynamics for the piezoelectric and magnetostrictive phases, expressions are obtained for the current/voltage conversion coefficient of the gyrator in terms of the phase parameters of the heterostructure. An experimental sample of a gyrator based on the Metglas/PZT/Metglas heterostructure was fabricated. Theoretically calculated and experimentally studied the frequency and load characteristics of the gyrator. It is shown that theoretical calculations are in good agreement with experimental data. Recommendations for the creation of gyrators with the highest current/voltage conversion efficiency are presented.

Tailoring the magnetomechanical power efficiency of metallic glasses for magneto-electric devices

Metallic glasses with high magnetomechanical power efficiency are widely used in laminated magneto-electric devices, from passive magnetometers and solid-state converters to very-low-frequency emitters. The remaining challenge is to simultaneously enhance the magnetomechanical power coupling and quality factors that are usually counterbalanced in metallic glasses. Here, we investigate the relaxations and surface configurations in annealed metallic glasses and their impacts on the magnetomechanical properties. We found an opportune annealing condition that maximizes the power efficiency when a surface-oxidation film of boron oxide is formed with excessive boron atoms that are separated from a surface-crystalline film. We confirm the findings by demonstrating a magneto-electric gyrator that has a power efficiency of 96% and magneto-electric antennas that have an increased emission intensity by 20% than that with traditionally annealed metallic glasses.

Effects of magnetic-elastic anisotropy on magnetoelectric gyrator with ferrite/PZT/ferrite laminate for enhancement of power conversion efficiencies

Effects of magnetic-elastic anisotropy on ferrite/lead zirconate titanate (PZT)/ferrite magnetoelectric (ME) gyrators were investigated for power conversion efficiency further improvement, and a methodology was introduced by changing the direction of applied magnetic field (HDC). Simulation by using finite element method provides a clear evolution of magnetic flux density distribution in ferrite as HDC rotates. Consequently, enhanced ME coupling as well as power conversion efficiency (PE) was achieved under a certain angle with maximum effective magnetic field applied especially at intensive magnetic fields. Experimental results show that current (I)-voltage (V) versus directional angle (θ) between HDC direction and longitudinal direction of ME sample and PE vs θ data can essentially track the dynamic piezomagnetic coefficient (DPMC) vs θ profile, indicating that the HDC rotation induced anisotropic magneto-elastic variations are responsible for the eventual PE improvement. For higher HDC = 98Oe, PE reaches its maximum of 76.5% at θ = 75˚ relative to its counterpart of 47.6% at θ = 0˚, exhibiting an approximately 1.69 times higher enhancement. Therefore, the feasibility of an efficient approach was verified by the obtained results, providing possibilities for PE further improvement and enhanced flexibilities for ME gyrator design.

Non-reciprocal voltage–current and impedance gyration effects in ferrite/piezoelectric toroidal magnetoelectric composites

A compact, efficient, and passive magnetoelectric (ME) gyrator consisting of a toroidal ferrite/piezoelectric composite and coil was developed, and its non-reciprocal V–I/I–V and bidirectional impedance conversion properties were systemically characterized. When a maximum V/I coefficient of 115 V/A over RL > 10 kΩ was obtained for the direct ME effect configuration, the output power reaches its maximum of 2.59 μW for optimum RL = 65 Ω at a constant input density of 48.4 μW/cm3, and when an inverse I/V coefficient was obtained, the output power reaches its maximum at 1.4 mA/V and 0.83 μW under optimum RL = 260 Ω and a constant input of 32.3 μW/cm3. Correspondingly, resistance-controlled capacitive/inductance tunabilities of 31 pF/Ω and 0.37 μH/Ω were achieved. Compared to traditional rectangular ME gyrators, the toroidal one has desired electromagnetic interference (EMI) tolerances due to its lower shape-induced anisotropy, near-zero demagnetization effects, and closed magnetic circuit. These findings provided more flexibility of the device design for efficient and compact power electronics deployed in circumstances where the lower EMI at higher frequencies was required.

Influence of shape on power conversion efficiency of Ni-Zn ferrite/piezoelectric magnetoelectric gyrator

Reducing the demagnetization effects via shape optimization in tri-layer magnetoelectric (ME) composite is an effective way to improve its power transfer conditions. To accomplish this goal, enhanced dynamic piezomagnetic coefficient of Ni0.7Zn0.3Tb0.02Fe1.98O4 ferrite, the tri-layer Ni0.7Zn0.3Tb0.02Fe1.98O4/PZT/Ni0.7Zn0.3Tb0.02Fe1.98O4 ME composites under different L/W ratios with coil wound around for gyrator fabrication were systematically characterized. Measurements of resonance ME responses were carried out for samples with the varying L/W ratio, the weak demagnetization field occurs at the sample with highest L/W ratio, yielding a stronger ME coupling. Experiment results of PE characterizations demonstrated that maximum of 91.3% was achieved under optimum bias and EMR driving in sample with higher L/W=17.5. Therefore, the higher PE is originated from strong dynamic magneto-mechanical response under the shape optimizations. These findings provide the possibility of ME gyrator in high energy conversion power electronics devices.

A Passive Tunable Magnetoelectric Gyrator: A Highly Efficient Approach to Non-Power Consumable Capacitor Control Methods

Tunability in magnetoelectric (ME) gyrators is of importance for realizing controllable energy-efficient electronics. Here, we investigated a novel passive control method that exhibits a high frequency tunability of up to 370 Hz using a non-power-consuming (passive) capacitor approach. The method requires zero external controllable power as the frequency is changed. This tuning does not decrease the power conversion efficiency (86%) of the gyrator. Our results indicate that the internal mechanical reactive components need to be changed by passive external capacitors, which proves to be an effective way by which gyrators can achieve high tunability and retain high power conversion efficiency. This article opens an approach toward the design of new tunable circuit components.

A Piezoelectric Mn-Doped PMN-PT/Metglas Magnetoelectric Gyrator: Enhanced Power Efficiency at Reduced Size

Magnetoelectric (ME) composites with ferromagnetic and ferroelectric phases show a strong coupling between the magnetic and electric subsystems that occurs through mechanical strain. Such composites are suitable for applications such as transducers that convert magnetic and electric energies. An important issue that needs to be considered is the magnetic-to-electric energy conversion efficiency. For applications under high power, energy transduction requires a high mechanical stability that minimizes the loss during conversion. Here, the high drive mechanical stability of Mn-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) crystals has been enhanced by external magnetic field when bonded to Fe-rich Metglas foils. External field modulation stabilizes the mechanical quality factor under high power drive. A magnetoelectric gyrator was then made that had an excellent power conversion efficiency of $\eta ={92}$ %, but which also had a dramatically decreased size as compared to similar gyrators made of “hard” Pb(Zr,Ti)O3 (PZT) ceramics. The findings provided an approach to optimizing the size-weight-power space of ME gyrators for power converters.

Dimension effects of a magnetoelectric gyrator with FeCoSiB/Pb(Zr,Ti)O3 layered composites core for efficient power conversion

A Magneto-Electric (ME) gyrator with a superior power efficiency of 95 % has been achieved based on a two-phase solid-state ME laminate. This ME gyrator consists of a winding coil that generates a magnetic field as the first step to realize electromagnetic energy transfer. A magneto-electric composite, serving as the second step, then converts the power from magnetic to electric forms. The laminate consists of two iron-cobalt based amorphous alloy layers bonded to a lead zirconate titanate plate. It has a giant magneto-electric coefficient of around 2200 (V/cm)/Oe at its mechanical resonant frequency (≈ 44 kHz) in structure. Approaching methods based on maximum power transfer (MPT) efficiency theory and the equivalent loss factor (ELF) from the input port have been introduced to evaluate the power efficiency of the ME gyrator. The expected MPT efficiency is 96.5 % at a power volume density of 0.1 W/in3 (6.1 mWatt/cm3), and 93.2 % up to 20 W/in3 (1.22 W/cm3). The ELF explains that the magnetomechanical conversion efficiency is related to the volume of the magnetic phase which is the dominating term in the power efficiency.

Bar-shaped Magnetoelectric Gyrator

This paper reports a dual-resonance power transfer effect and a dual-resonance I-V conversion for a bar-shaped ME gyrator made from a hard Pb(ZrxTi1−x)O3 (PZT) ceramic bar having a transverse polarization and a Tb0.3Dy0.7Fe1.92 (Terfenol-D) magnetostrictive alloy bar having a longitudinal magnetization bonded along their cross-section areas. A bar-shaped provides several advantages to a ME gyrator; such as dual resonance frequency along its length direction, as well as half-wave and full-wave vibration modes; reduced laminate bonding area avoiding adhesive breakdown; and ease of fabrication. The reported magnetoelectric gyrator effect originates from the mechanically mediated resonance piezoelectric and magnetostrictive effects in the PZT and Terfenol-D bars, respectively. We studied the influence of the length ratio between the Terfenol-D and piezoelectric bars. A power efficiency of 69.4% was obtained at the half wavelength resonance of 21.47kHz under optimal HBias=1000 Oe and low power conditions. Under higher power drive of 8W/in3, an efficiency of 60.2% was found. This dual-resonance ME gyrator effect offers much promise in power transfer devices for power electronic applications.

Power Conversion Efficiency and Equivalent Input Loss Factor in Magnetoelectric Gyrators

Magnetoelectric (ME) gyrators are unique circuit elements capable of direct conversion of the current to voltage or vice versa. In order to understand the power conversion and loss processes in the gyrators, an equivalent input loss factor has been developed in this paper based on Mason's model (equivalent circuit model). This factor serves to understand the loss transferring mechanism and to evaluate the conversion efficiency for the electric power in ME gyrators. Studies have been carried out for modeling the power conversion in both the solenoid and the ME core. Several important factors have been proposed and discussed to enhance the conversion efficiencies in the electric–magnetic–mechanical three-phase conversion process. A simplification of our equations reveals that the efficiency of the ME gyrator is related to the product of the effective coupling ( k2 $_{\text{eff, m}}$ ) and mechanical quality ( Q mech). According to our model, magnetic and electric materials with high k $_{\text{eff, m}}$ and Q mech values are the key ingredients to enhance the efficiency of ME gyrators. We have successfully realized a power efficiency of 92% based on a Metglas/hard-PZT ME gyrator, which showed a good correlation to the predicted values.

Highly efficient power conversion in magnetoelectric gyrators with high quality factor.

A high-Q magnetoelectric (ME) gyrator consisting of a trilayer laminate of nickel-iron-based constant elasticity alloy (Ni-Fe-Cr) and lead zirconate titanate with a coil wound around it has been developed and systematically characterized. Highly efficient magneto-mechanical-electric conversion can be achieved by means of the combination contributions of high quality factors from individuals, and much energy can be transferred through the gyration device. Under an electromechanical resonance frequency of 54.04 kHz, experimental results show that maximum efficiency reaches as high as 88.5% under an extremely low input density of 3.31 µW/cm3 with an optimum load resistance of 9.6 kΩ and a magnetic bias of 66 Oe. Such a highly efficient ME gyrator with a high Q factor can be beneficial or degrade the design goals that are likely to be achievable for practical applications in compact power transfer electronic devices.

A passive isolator realized by magnetoelectric laminate composites

This work demonstrates a passive isolator realized by magnetoelectric laminate composites. The proposed isolator consists of a magnetoelectric gyrator, two impedance matching networks, and a load impedance. The equivalent circuit model of the isolator is developed. Good agreement has been obtained between the measured and computed results based on the proposed equivalent circuit model. The measured forward insertion loss and reverse isolation of the proposed isolator are 4.7 dB and 19 dB, respectively. A figure-of-merit which determines the performance of the isolator is proposed, which can be used to guide the design of such isolators.

A dual-output magnetoelectric gyrator

A novel dual-output magnetoelectric (ME) gyrator operating in an acoustic resonance mode and based on a Pb(ZrxTi1−x)O3 (PZT)/Metglas/PZT (P–M–P) trilayer structure is discussed. The dual-output with different current-to-voltage (I–V) conversion ratios and different voltage levels result from the use of piezoelectric layers with different thicknesses as the output capacitive port. Under open circuit conditions, the maximum I–V conversion ratios of the two outputs were 5.7 and 13.5 kV A−1 at a frequency of 50.4 kHz. A high power efficiency (ƞ) of 91.7% was achieved and remained relatively stable (⩾86%) under increasing power drive to a power density of 45 W in−3. These excellent power transfer and multi-output characteristics offer unique possibilities for possible use of ME gyrators in modern power electronic devices.

Stability enhancement of yttrium substituted nickel zinc ferrite/PZT magnetoelectric gyrators under high power conditions

The influence of yttrium (Y) ion substitution on the magneto-mechanical properties of nickel-zinc ferrite (Ni0.7Zn0.3YxFe2-xO4) or NZFO-Y and the power efficiency (η) of magnetoelectric (ME) gyrators consisting of NZFO-Y/Pb(Zr, Ti)O3 layers were studied. X-ray diffraction (XRD) of polycrystalline samples of NZFO-Y indicated that yttrium incorporated into the crystal lattice resulted in an enlargement of the lattice parameter. Also, the density and ionic hopping length were increased, and the porosity was decreased. Together, these resulted in significant changes in the magneto-mechanical coupling (k33,m) and mechanical quality (Qm) factors. It was found that k33,m decreased with the increasing Y content for 0 ≤ x ≤ 0.08, whereas Qm was increased. For x > 0.05, the values of k33,m and Qm were found to be nearly stable with increasing input power density (PD-Ms) up to 47 W/in3. Under this high power driving condition for 20 min, we found that the power conversion stability of ME gyrators was increased with the increasing Y content in the ferrite and that a maximum power conversion efficiency occurred near 77%. These findings offer the potential for ferrite-based ME gyrator applications in power electronic conversion devices.

A Highly Efficient Self‐Biased Nickel‐Zinc Ferrite/Metglas/PZT Magnetoelectric Gyrator

A high efficiency self‐biased magnetoelectric (ME) gyrator operating under zero magnetic bias field (HBias = 0) was developed. It consists of a three‐phase nickel‐zinc ferrite/Metglas/piezoelectric longitudinal–transverse (L‐T) ME laminate and a solenoid. Laminates with different length–width (L/W) ratios, together with various thickness (number of Metglas foils) ratios between ferrite and Metglas layers, were studied. A maximum power conversion efficiency (η) of 72% was found at the fundamental electromechanical resonance for a high L/W ratio of 18.7. The high zero‐bias η could be attributed to a higher mechanical quality factor (Qm) and the low demagnetization effect (Nz) of nickel‐zinc ferrite laminates of higher L/W. Eliminating the external magnetic bias will facilitate miniaturization of ME gyrators for use in portable electronics and medical applications.

Enhanced stability of magnetoelectric gyrators under high power conditions

In this study, three different coil-based magnetoelectric (ME) gyrators of different geometries, including gyrators with high power output, have been designed and characterized. These included two magnetostrictive/piezoelectric/magnetostrictive (M-P-M) and one piezoelectric/magnetostrictive/piezoelectric (P-M-P) type ME gyrators, which consisted of nickel zinc ferrite (NZFO) and lead zirconate titanate (PZT) ceramic plates. Compared with M-P-M ME gyrators, the P-M-P ones exhibited a higher power efficiency (η) of 85% when operated at resonance under an optimal magnetic bias field (HBias) of 40 Oe at low power conditions. It retained a relatively high efficiency of η = 79% under a high input power density of 2.87 W/cm3. A low reduction in the magnetomechanical coupling and mechanical quality (k33,m and Qm) factors of the NZFO ferrite layer in the ME gyrator explains the resilience of the P-M-P type structure with increasing power drive. The findings open the possibility of using ME gyrators in high power applications.

Highly efficient solid state magnetoelectric gyrators

An enhancement in the power-conversion-efficiency (η) of a magneto-electric (ME) gyrator has been found by the use of Mn-substituted nickel zinc ferrite. A trilayer gyrator of Mn-doped Ni0.8Zn0.2Fe2O3 and Pb(Zr,Ti)O3 has η = 85% at low power conditions (∼20 mW/in3) and η ≥ 80% at high power conditions (∼5 W/in3). It works close to fundamental electromechanical resonance in both direct and converse modes. The value of η is by far the highest reported so far, which is due to the high mechanical quality factor (Qm) of the magnetostrictive ferrite. Such highly efficient ME gyrators with a significant power density could become important elements in power electronics, potentially replacing electromagnetic and piezoelectric transformers.

Power conversion efficiency and resistance tunability in coil-magnetoelectric gyrators

The power efficiency and resistance tunability of magnetoelectric (ME) gyrators consisting of two-phase magnetostrictive-piezoelectric ME longitudinal-transverse (L-T) mode sandwich laminates and coils, have been studied. The copper wire coil provided an inductance-based coil port (CoilP) and the piezoelectric layer of the ME laminate provided a capacitance-based ME port (MEP). The device behaved as a 2-port 4-wire ME gyrator. The current-to-voltage and voltage-to-current (I-V and V-I, respectively) conversion ratios, resistance-inductance/capacitance tunabilities (TR-L and TR-C, respectively) and direct/converse power efficiencies (PED and PEC, respectively) were measured. Maximum values of 1454 V/A and 0.468 mA/V for the I-V and V-I conversion ratios, 76 μH/Ω and 0.17 pF/Ω for TR-L and TR-C coefficients, and ∼35% for both PED and PEC were found by measuring the performance characteristics. Compared with the electromagnetic and piezoelectric transformers, ME gyrators have good input and output characteristics that change the capacitance and inductance features of the input and output ports. Our findings open a promising direction for developing a generation of converters for power electronics.

Time-domain simulation of mixed nonlinear magnetic and electronic systems

This paper describes a technique for the simulation of complex magnetic systems intimately connected to any necessary drive electronics. The system is split into two Kirchhoffian domains, one magnetic and one electric. Two-way interaction between the domains is supported by a virtual device called a magnetoelectric differential gyrator. With this technique, arbitrarily complex, nonlinear, hysteretic magnetic systems may be simulated in the time domain, coupled to any appropriate nonlinear electronics, at a fraction of the cost of a comparable finite-element calculation. The capabilities of the system are demonstrated by the simulation of a feedback-controlled current-sensing system, and the simulation tracks the measured behavior of the system well outside its linear region, to the point that the nonlinear hysteretic core is being driven into and out of saturation, a consequence of a time delay inherent in the electronics. This is compared with a conventional electronic simulation of the same system, and the increased accuracy of this technique is clearly demonstrated.