Magnetoelectric Coupling Characteristics Research Articles

Direct fabrication of single-phase multiferroic BiFe0.95Co0.05O3 films on polyimide substrates for flexible memory

• Low-temperature prepared BiFe 0.95 Co 0.05 O 3 films exhibited excellent characteristics. • A solution-based seeded photocatalytic precursor method has been developed. • The physical mechanism of the low-temperature prepared films is explained. Multiferroic memory exhibits unusual physical properties due to the electrical writing and magnetic reading of data to achieve low power consumption and efficient data processing. The flexibility of the multiferroic memory can realize its application in portable and wearable smart electronic products. The main challenge of integrating multiferroic oxides onto flexible substrates is to lower their processing temperature below the degradation temperature of plastic substrates. In this paper, the bendable inorganic BiFe 0.95 Co 0.05 O 3 polycrystalline thin films were prepared directly on flexible polyimide substrates with Pt electrode at only 350 ℃ by solution-based seeded photocatalytic precursor method. The flexible multiferroic element could bend safely to a small bending radius of 3 mm and exhibited excellent ferroelectricity, ferromagnetic, and magnetoelectric coupling characteristics at room temperature. Its remanent polarization was as high as 36 μC/cm 2 , remanent magnetization up to 4110 A/m, and magnetoelectric coupling coefficient up to 0.0135 V/A. The polarization did not deteriorate significantly during 10 3 bending-release cycles, 10 7 fatigue cycles, and 10 4 s data retention.These results prove the concept of integrating single-phase multiferroic thin films and flexible plastic substrates with low temperature by seeded photocatalytic precursor method and demonstrate the application potential of single-phase multiferroic films prepared at low temperature in the next generation of flexible multiferroic memory.

Significant impact of spinel ferrites in evolution of magneto-electric coupling in novel tri-phase composites

Multiferroic materials have played an important role in recent technological breakthroughs because of their intrinsic magneto-electric coupling characteristics. In this framework, a cost effective and reliable sol–gel auto-combustion method was used to synthesize the 0.8[(1-x) BiFeO3 + xFe3O4] + 0.2Cr2O3 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1) nanocomposites. X-ray diffraction was used to identify three phases and their unique crystal parameters. Elemental composition of the samples was verified using an energy dispersive X-ray spectroscopy. Field emission scanning electron microscopy revealed distinct, well-shaped, and spherical grains when the spinel-ferrite contents were introduced to the series. An irregular behavior in the bulk porosity was observed, courtesy to the ImageJ software. The vibrating sample magnetometer, operated at ±7 kOe, showed an increase in saturation magnetism. A rigorous analysis of recoverable energy density, energy loss density, and other ferroelectric parameters had been presented, demonstrating the potential of the proposed recipe for energy storage devices. The synthesized specimens demonstrated remarkable magneto-electric coupling at optimal content levels.

Anisotropic magnetoelectric functionality of ferromagnetic shape memory alloy heterostructures for MEMS magnetic sensors

In this report, the ferromagnetic shape memory alloy (Ni50Mn35In15) and Pb0.96La0.04Zr0.52Ti0.48O3 based bilayer (Ni-Mn-In/PLZT (260 nm/300 nm)), trilayer (Ni-Mn-In/PLZT/Ni-Mn-In (130 nm/300 nm/130 nm)) and four-layer (Ni-Mn-In/PLZT/Ni-Mn-In/PLZT (130 nm/150 nm/130 nm/150 nm)) multiferroic heterostructures with equal thickness ratios have been fabricated over Si substrates via DC/RF magnetron sputtering technique. The in-plane and out-of-plane magnetic hysteresis curves show the anisotropic nature of the ferromagnetic layer. The anisotropic magnetoelectric coupling characteristics have been investigated for all the fabricated devices by recording the induced magnetoelectric coupling voltages under both parallel and perpendicular applied magnetic fields to the plane of the device. Compared to all fabricated heterostructures, the trilayer structure exhibits the highest magnetoelectric coupling coefficients with 1.56 V/(cm Oe)-1 and 2.01 V/(cm Oe)-1 in longitudinal and transverse configurations, respectively. This anisotropic nature of magnetoelectric coupling can be used to measure the applied magnetic field direction. The rarely reported anisotropic AC magnetic field sensing parameters of the fabricated devices like Pearson’s r, sensitivity, and inaccuracy have been calculated. The trilayer device exhibits excellent AC magnetic field sensing parameters with inaccuracy, sensitivity, and linearity of 1.856% full-scale output (FSO), 0.63 mV cm−1 and 0.9993 in longitudinal configuration while 1.755% FSO, 1.18 mV Oe−1, and 0.9993 in the transverse configuration, respectively. Such nanoscale ferromagnetic shape memory alloys based symmetric multilayered multiferroic heterostructures pave the way for the design and development of futuristic MEMS magnetoelectric magnetic field sensor to detect the magnetic field and its spatial orientation.

Magnetoelectric coupling tailored by the orientation of the nanocrystals in only one component in percolative multiferroic composites.

Novel 1–3 type multiferroic composite thin films were prepared via a simple 0–3 composite fabrication process. The orientation of the Ni0.5Zn0.5Fe2O4 (NZFO) nanocrystals in the BaTiO3–Ni0.5Zn0.5Fe2O4 (BTO–NZFO) composite thin films was controlled by magnetron sputtering, and the controlling effect of such orientation on magnetoelectric coupling was investigated in detail. The NZFO lattice in the BTO–NZFO composite thin films grew with (100) orientation under the induction of the (111) plane of Si. The transfer of substrate stress between the closely contacted grains also contributes to the orientation of the NZFO nanocrystals. The 0.6BTO–0.4(100)NZFO multiferroic composite thin film exhibited a magnetization strength of 9.2% at the Curie point of the BTO phase, showing extremely strong magnetoelectric coupling characteristics. This work provides an effective strategy for the development of high-performance multiferroic composites, and brings about new conception of realizing strong magnetoelectric coupling effect from the perspective of physical chemistry.

A quasistatic hysteresis model for magnetoelectric effect in multiferroic nanostructured films with surface effect

The investigation of hysteresis induced self-biased magnetoelectric (ME) coupling in multiferroic nanostructured films is significant for self-biased nano-devices. In this paper, we propose a quasistatic hysteresis model for ME effect in multiferroic nanostructured films based on surface stress model and multi-field coupled hysteretic constitutive model. For an asymmetric structure consisting of different magnetostrictive phases, the flexural strain is considered in the theoretical model. It is revealed that ME coupling in ME composites with nano-scale thickness is significantly size-dependent below critical size, which is enhanced by surface effect. Self-biased ME hysteretic behavior can be observed by considering the hysteretic effect of magnetostrictive materials, resulting in a large ME voltage coefficient in absence of bias magnetic field. The self-biased ME voltage coefficient is affected by pre-stress and thermal variation due to the complex magneto-elastic-thermal coupling characteristics of constituent materials. The proposed model provides a method to analyze and evaluate the nonlinear ME coupling characteristics of self-biased nano-devices operating under extreme stress or temperature conditions.

Flexible magnetoelectric transducer with high magnetic field sensitivity based on Metglas/poly(vinylidene fluoride) heterostructures

In this paper, the flexible magnetoelectric (ME) transducer consisting of FeSiB (Metglas)/poly(vinylidene fluoride) (PVDF) is presented, whose ME coupling characteristics and ME sensing performance under different bend status have been investigated. It is found that an appropriate size of transducers is propitious to the ME coupling characteristics due to the demagnetization effect. In addition, with increase the bending angle (θ) of transducers from 0° to 50°, the magnetoelectric voltage coefficient (MEVC) shows a reduction from 240.42 to 26.44 V/cm·Oe and 13.1 to 2.11 V/cm·Oe, at the resonance and low-frequency (1 kHz), respectively. Meanwhile, the induced ME voltage have an excellent linear relationship to ac magnetic field. An ultrahigh magnetic field sensitivity of 1.22 V/Oe and 0.11 V/Oe have been found under θ = 0° and 50°, respectively, which are positively comparable to the highest reported in the most recent polymer-based ME transducers. Moreover, the transducers can maintain the MEVC stable after an additionally bending cycles up to 1000 times, indicating the full flexibility and high stability of the mentioned transducers. Obviously, it demonstrates that the proposed FeSiB/PVDF transducers have great potential of being applied to wearable devices.

A high-sensitivity zero-biased magnetoelectric sensor using five-phase laminate composites based on FeCoV nanocrystalline soft magnetic alloy

This paper present a high-sensitivity zero-biased ME sensor consists of FeCoV/Terfenol-D/Pb(Zr1-x,Tix)O3(PZT)/Terfenol-D/FeCoV (FMPMF), whose magnetoelectric (ME) coupling characteristics and ME sensing performance have been investigated. Compared to traditional Terfenol-D/PZT/Terfenol-D (MPM) sensor, the zero-biased ME coupling characteristics of FMPMF sensor were significantly improved. Meanwhile, the induced zero-biased ME voltage of FMPMF sensor shows an excellent linear relationship to ac magnetic field both at the low frequency (1kHz) and the resonant frequency (115.14 kHz). The measured sensitivity at resonance is 1.95 V/Oe and the output resolution is approximately 2.43×10-8T. The proposed FMPMF sensors still have very good performance in the current sensing. The measured results shows an average sensitivity of 1.14 mV/A with highly linear behavior in the current range 1 A to 10 A at 50 Hz. Remarkably, it indicates that the proposed zero-biased miniature ME sensor give the prospect of being able to applied to the field of highly sensitive current sensing for the electricity monitoring in electric power grid.

Magnetoelectric coupling characteristics in multiferroic heterostructures with different thickness of nanocrystalline soft magnetic alloy

Magnetoelectric(ME) coupling characteristics in multiferroic heterostructures with different thickness of nanocrystalline soft magnetic alloy has been investigated at low frequency. The ME response with obvious hysteresis, self-biased and dual-peak phenomenon is observed for multiferroic heterostructures, which results from strong magnetic interactions between two ferromagnetic materials with different magnetic properties, magnetostrictions and optimum bias magnetic fields Hdc,opti. The proposed multiferroic heterostructures not only enhance ME coupling significantly, but also broaden dc magnetic bias operating range and overcomes the limitations of narrow bias range. By optimizing the thickness of nanocrystalline soft magnetic alloy Tf, a significantly zero-biased ME voltage coefficient(MEVC) of 14.8mV/Oe (185 mV/cm⋅ Oe) at Tf = 0.09 mm can be obtained, which is about 10.8 times as large as that of traditional PZT/Terfenol-D composite with a weak ME coupling at zero bias Hdc,zero. Furthermore, when Tf increases from 0.03 mm to 0.18 mm, the maximum MEVC increases nearly linearly with the increased Tf at Hdc,opti. Additionally, the experimental results demonstrate the ME response for multiferroic heterostructures spreads over a wide magnetic dc bias operating range. The excellent ME performance provides a promising and practicable application for both highly sensitive magnetic field sensors without bias and ME energy harvesters.

Magnetoelectric Coupling Characteristics of Multiphase Laminate Heterostructures Based on FeCuNbSiB Nanocrystalline Soft Magnetic Alloy

Over the last decade, multiferroic laminate heterostructures, consisting of the piezoelectric layer (such as PZT) and the magnetostrictive layer (such as Terfenol-D), have attracted considerable attention due to their high Curie or Neel temperature and large magnetoelectric (ME) effect at room temperature. The ME laminate materials have demonstrated potential in many applications such as transducers, actuators, magnetic field sensors, energy harvesters, and other devices [1]. ME effect in the multiferroic laminated heterostructures is essentially attributed to the elastic coupling between the piezoelectric and magnetostrictive layers [2]. The effective piezomagnetic coefficient and effective mechanical quality factor play a key role in the performance of the ME materials. However, owing to the small values of the mechanical quality factor and relative permeability, the ME voltage coefficient of the traditional Terfenol-D/PZT (MP) composites is difficult to increase [3, 4]. The nanocrystalline FeCuNbSiB soft magnetic alloy would be a good solution, according to the large interface stress-strain coupling effects. In this paper, a series of FeCuNbSiB/Terfenol-D/PZT (F/M/P) multi-phase laminate heterostructures are presented (Fig. 1), whose ME coupling characteristics have been investigated. Compared to traditional MPM, the ME coupling characteristics of the proposed FMPMF heterostructures were significantly improved. The resonant and low-frequency ME voltage coefficient of the proposed F/M/P heterostructures could be tuned by controlling the layer numbers N. When N is 7 (FMPMPMF), the maximum value of resonant ME voltage coefficient achieves 8.69 V/Oe, which is about 3.65 times higher than that for FMP, 1.81 times higher than that for FMPMF (Fig. 2(a)). Meanwhile, the maximum value of low-frequency ME voltage coefficient for FMPMPMF heterostructures achieves 69.6 mV/Oe at H b =378 Oe (Fig. 2(b)). Remarkably, it indicates that the F/M/P heterostructures have great potential as far as its application in highly sensitive dc magnetic field sensing and vibration energy harvesting.

Equivalent circuit model including magnetic and thermo sources for the thermo–magneto–electric coupling effect in magnetoelectric laminates**Project supported by the National Natural Science Foundation of China (Grant Nos. 11172285 and 11472259) and the Natural Science Foundation of Zhejiang Province, China (Grant No. LR13A020002).

The nonlinear thermo–magneto–mechanical magnetostrictive constitutive and the linear thermo–mechanical-electric piezoelectric constitutive are adopted in this paper. The bias magnetic field and ambient temperature are equivalent to a magnetic source and a thermo source, respectively. An equivalent circuit, which contains a magnetic source and a thermo source at the input, for the thermo–magneto–electric coupling effect in magnetoelectric (ME) laminates, is established. The theoretical models of the output voltage and static ME coefficient for ME laminates can be derived from this equivalent circuit model. The predicted static ME coefficient versus temperature curves are in excellent agreement with the experimental data available both qualitatively and quantitatively. It confirms the validity of the proposed model. Then the models are adopted to predict variations in the output voltages and ME coefficients in the laminates under different ambient temperatures, bias magnetic fields, and the volume ratios of magnetostrictive phases. This shows that the output voltage increases with both increasing temperature and increasing volume ratio of magnetostrictive phases; the ME coefficient decreases with increasing temperature; the ME coefficient shows an initial sharp increase and then decreases slowly with the increase in the bias magnetic field, and there is an optimum volume ratio of magnetostrictive phases that maximize the ME coefficient. This paper can not only provide a new idea for the study of the thermo–magneto–electric coupling characteristics of ME laminates, but also provide a theoretical basis for the design and application of ME laminates, operating under different sensors.

Self-biased magnetoelectric coupling characteristics of three-phase composite transducers with nanocrystallin soft magnetic alloy

This paper reports the self-biased magnetoelectric (ME) effects in composites consisting of high-permeability Fe-based nanocrystalline soft magnetic alloy Fe73.5Cu1Nb3Si13.5B9 (FeCuNbSiB), pure nickel (Ni) and piezoelectric lead zirconate titanate (PZT). The FeCuNbSiB ribbons are fabricated on traditional laminates Ni/PZT/Ni through two modes: the attached mode (F–NPN–F) and the laminated mode (F/NPN/F). The F–NPN–F composite sufficiently reveals that the high-permeability FeCuNbSiB ribbons concentrate more magnetic flux in magnetostrictive Ni, which results in the self-biased ME effects of F–NPN–F. For the F/NPN/F composite, the FeCuNbSiB acts as the dynamic driver to enhance the effective piezomagnetic coefficient of Ni. The giant self-biased ME effects of F/NPN/F are because of the internal magnetic field between Ni and FeCuNbSiB due to their different magnetic characteristics. The influences of the numbers of FeCuNbSiB layers (L) on the resonant ME voltage coefficients (α ME,r ) for F–NPN–F and F/NPN/F composites are investigated in detail. The experiments demonstrate that the maximum α ME,r at zero-biased field is 80 V/cm Oe for F–NPN–F with L = 2, and 85 V/cm Oe for F/NPN/F with L = 4. This paper demonstrates that these two ME composites are suitable for achieving zero-biased ME transducers, power-free magnetic field sensors and energy harvesters.

Multipeak self-biased magnetoelectric coupling characteristics in four-phase Metglas/Terfenol-D/Be-bronze/PMN-PT structure

This letter develops a self-biased magnetoelectric (ME) structure Metglas/Terfenol-D/Be-bronze/PMN-PT (MTBP) consisting of a magnetization-graded Metglas/Terfenol-D layer, a elastic Be-bronze plate, and a piezoelectric 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 (PMN-PT) plate. By using the magnetization-graded Metglas/Terfenol-D layer and the elastic Be-bronze plate, multi-peak self-biased ME responses are obtained in MTBP structure. The experimental results show that the MTBP structure with two layers of Metglas foil has maximum zero-biased ME voltage coefficient (MEVC). As frequency increases from 0.5 to 90 kHz, eleven large peaks of MEVC with magnitudes of 0.75-33 V/(cm Oe) are observed at zero-biased magnetic field. The results demonstrate that the proposed multi-peak self-biased ME structure may be useful for multifunctional devices such as multi-frequency energy harvesters or low-frequency ac magnetic field sensors.

The giant magnetoelectric effect in Fe73.5Cu1Nb3Si13.5B9/PZT thick film composites

The Fe73.5Cu1Nb3Si13.5B9/PZT thick film composites with excellent magnetoelectric (ME) coupling effect were synthesized by electrostatic spray depositing. The ME coupling characteristics of Fe73.5Cu1Nb3Si13.5B9/PZT thick film composites were investigated. It is found that the appropriate thickness ratio between magnetostrictive layers and piezoelectric layers (tm/tp) will be favorable to raise the resonance ME field output performance. The resonance frequency of ME field coefficient can be tuned by controlling tm/tp. The optimum resonance ME field coefficient of Fe73.5Cu1Nb3Si13.5B9/PZT thick film composites achieves 259.2 V/cm Oe at mechanical resonance frequency at 11.5 kHz with the dc bias magnetic field is 60 Oe. Remarkably, the proposed composites exhibit a giant ME effect and a higher ME voltage coefficient than the previous Terfenol-D/PZT laminated composites. It indicates that the mentioned Fe73.5Cu1Nb3Si13.5B9/PZT thick film composites have great potential for the application of highly sensitive magnetic field sensing and vibration energy harvesting.

Giant self-biased magnetoelectric coupling characteristics of three-phase composite with end-bonding structure

This paper develops a self-biased magnetoelectric (ME) heterostructure FeCuNbSiB/Ni-PZT-FeCuNbSiB/Ni (FN-P-FN) by bonding magnetization-graded FeCuNbSiB/Ni layers at the free ends of piezoelectric Pb(Zr,Ti)O3 (PZT) plate. By using the magnetization-graded magnetostrictive layer and end-bonding heterostructure, giant self-biased ME responses and obvious hysteresis are observed in FN-P-FN heterostructure. The experimental results show that the zero-biased ME voltage coefficient of FN-P-FN heterostructure reaches ∼183.2 (V/cm Oe), which is ∼2.1, ∼4.5, and ∼41.6 times higher than that of FeCuNbSiB/Ni/PZT, Ni-PZT-Ni, and FeCuNbSiB-PZT-FeCuNbSiB composites, respectively. The results indicate that the proposed three-phase end-bonding heterostructure shows promising applications for high-sensitivity self-biased magnetic field sensors and ME transducers.

Magnetoelectric coupling characteristics of five-phase laminate composite transducers based on nanocrystalline soft magnetic alloy

A five-phase laminate composite transducer based on nanocrystalline soft magnetic FeCuNbSiB alloy is presented, whose magnetoelectric (ME) coupling characteristics have been investigated. It is found that the resonant ME voltage coefficient of FeCuNbSiB/Terfenol-D/Pb(Zr1-x,Tix)O3 (PZT)/Terfenol-D/FeCuNbSiB (FMPMF) five-phase transducer is much larger than that of traditional Terfenol-D/PZT/Terfenol-D (MPM) transducer, resulting from the enhancement of the effective mechanical quality factor and effective piezomagnetic coefficient of the transducers. Appropriate FeCuNbSiB layer thickness is propitious to the resonant and low-frequency ME coupling characteristics. The maximum resonant ME voltage coefficient achieves 4.81 V/Oe with FeCuNbSiB layer thickness is 60 μm under the DC bias magnetic field Hb = 77 Oe, which is 1.48 times as great as that of traditional MPM transducer. In addition, the maximum ME voltage coefficient at low frequency is 51.2 mV/Oe under the DC bias magnetic field Hb = 442 Oe, which is 1.26 times as great as that of traditional MPM transducer. It indicates that the mentioned five-phase laminate composite transducers have great potential for the application of highly sensitive dc magnetic field sensing and vibration energy harvesting.

Enhanced magnetoelectric coupling in transition-metal-doped BiFeO3 thin films

The transition-metal (TM) doped BiFeO3 thin films have been deposited on Si (100) substrate by spray pyrolysis technique and their electric, magnetic, ferroelectric and magnetoelectric properties were studied. The leakage current in Mn- and Co-doped BiFeO3 have been found to be about one order magnitude lower than that of BiFeO3 sample. The improvement in magnetization (Ms) and polarization (Pr) have been found in the TM doped BiFeO3 samples and reaching a maximum value of Ms~0.21μB per formula unit for the Cr-doped and Pr~55.6μC/cm2 for Mn-doped samples. The study of magnetoelectric coupling characteristics gave optimum coupling coefficient at critical value of the magnetic field, which may be due to the suppression of cycloid spin structure. The maximum coupling sensitivity of 10.48V/cmOe was observed for Mn doped samples.