This paper investigates the possibilities of creating magnetic field sensors using the direct magnetoelectric (ME) effect in a monolithic heterostructure of amorphous ferromagnetic ...material/langatate. Layers of 1.5 μm-thick FeCoSiB amorphous ferromagnetic material were deposited on the surface of the langatate single crystal using magnetron sputtering. At the resonance frequency of the structure, 107 kHz, the ME coefficient of linear conversion of 76.6 V/(Oe∙cm) was obtained. Furthermore, the nonlinear ME effect of voltage harmonic generation was observed with an increasing excitation magnetic field. The efficiency of generating the second and third harmonics was about 6.3 V/(Oe
∙cm) and 1.8 V/(Oe
∙cm), respectively. A hysteresis dependence of ME voltage on a permanent magnetic field was observed due to the presence of α-Fe iron crystalline phases in the magnetic layer. At the resonance frequency, the monolithic heterostructure had a sensitivity to the AC magnetic field of 4.6 V/Oe, a minimum detectable magnetic field of ~70 pT, and a low level of magnetic noise of 0.36 pT/Hz
, which allows it to be used in ME magnetic field sensors.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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•Planar magnetoelectric voltage transformer fabricated and investigated.•Transformer uses coilless excitation system instead of volumetric magnetic coils.•The voltage transformation ...ratio is magnetically tuned from zero to 13.2.
A planar magnetoelectric voltage transformer based on a layered composite structure containing layers of amorphous ferromagnet and piezoelectric lead zirconate-titanate has been fabricated and investigated. The transformer uses a coilless system (the so-called "magnetic capacitor") to excite the direct magnetoelectric effect at the frequency of the acoustic resonance of the structure, which made it possible to significantly simplify the design. The voltage transformation ratio of the magnetoelectric transformer, in contrast to the known electromagnetic or piezoelectric transformers, can be tuned by an external magnetic field from zero to 13.2 with an increase in the field from zero to 30 Oe. The operating range of the output voltage of the transformer is 0−400 mV, and the output power reaches 9 μW at optimal load resistance. The technique for calculating the characteristics of the transformer is described.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Industrial machines and mechanisms, household appliances, natural sources and biological objects generate weak magnetic fields with amplitudes of ~10–12 – 10–4 T in the frequency band of ~1–105Hz. ...Analysis of the fields’ characteristics allows to get information about internal processes and performance of these sources in a non-contact way, to carry out medical diagnostics. This makes topical the development of low-frequency magnetic field spectrum analyzers. The paper describes a spectrum analyzer of a new type using nonlinear effect of magnetic field mixing in a composite ferromagnet-piezoelectric heterostructure. The main element of the analyzer is a magnetic field mixer which contains a piezoelectric langatate single-crystal sandwiched between two layers of a magnetostrictive amorphous alloy. With simultaneous action of the measured magnetic field and the excitation magnetic field on the structure and fulfillment of the frequency matching conditions, the structure generates a voltage at the electromechanical resonance frequency. Swept-tuned spectrum analysis of the measured field is carried out by tuning the frequency of the excitation field. A prototype of the analyzer is fabricated and characterized. It operates in the frequency band of 0.1–85 kHz, has a frequency resolution of ~40 Hz, a minimum detectable field of 50 nT, and a dynamic range of 35 dB. Possibilities to improve characteristics of magnetic field spectrum analyzers are discussed.
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•A new swept-tuned spectrum analyzer of magnetic fields is proposed.•The analyzer uses resonant magnetoelectric effect of magnetic field frequency mixing.•A prototype of the spectrum analyzer is fabricated and characterized.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Theory and results of a systematic study on the nature of nonlinear magnetoelectric (ME) interactions in layered ferromagnetic and ferroelectric composites are discussed. The model that considers the ...nonlinearity associated with magnetostriction of the ferromagnet is to result in (i) a dc component and (ii) frequency doubling when the composite is subjected to an ac magnetic field. In the presence of two ac magnetic fields of different frequencies, nonlinear effects give rise to generation of ME voltages at the sum and difference of the fields frequencies. The efficiencies of nonlinear ME interactions are shown to be a function of the second derivative of the magnetostriction with respect to the bias magnetic field. The predictions of the model are compared with data for bilayers of lead zirconate titanate (PZT) and ferromagnetic layers with wide variations in saturation magnetostrictions and saturation magnetic fields, i.e., an amorphous ferromagnetic (AF) alloy, Ni, or permendur. Under linear excitation conditions an enhancement in the ME voltage is measured when the ac magnetic field is applied at the acoustic mode frequencies. Under nonlinear excitation conditions the mechanical deformation and the ME response occur at twice the excitation frequency and the AF-PZT composite shows a much higher nonlinear ME effects. In addition, the AF-PZT shows an efficient frequency mixing than the samples with Ni or permendur when subjected to two ac magnetic fields. The frequency mixing is shown to be of importance for magnetic field sensor applications.
•A theory for nonlinear magnetoelectric effects in composite structures is described.•The effects were observed in different planar magnetic-piezoelectric structures.•The nonlinearity of the magnetostriction results in mixing of magnetic fields.•The field mixing efficiency is determined by the 2-d derivative of magnetostriction.•New type of the frequency-selective ac magnetic fields sensors is suggested.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Abstract
The resonant magnetoelectric (ME) effect in a ring-type structure of nickel–lead zirconate titanate–Metglas amorphous alloy (Metglas 2605SA1) has been studied. The use of ring geometry and ...magnetic layers with different signs of magnetostriction and comparable saturation fields led to a noticeable enhancement in the ME coefficient and a decrease in the optimal bias field, as compared with two-layer planar heterostructures. At the frequency of radial acoustic oscillations of the structure and under circular magnetization, the ME coefficient of 6.4 V (Oe·cm)
−1
and ac field sensitivity of 0.6 V Oe
−1
were obtained for a permanent bias field of 2 Oe.
•Direct and converse magnetoelectric effects observed in flexible FeBSiC-PVDF structure.•Converse ME effect arises due to elastomagnetic nonlinearity of ferromagnetic layer.•Field dependences of ME ...conversion efficiencies are well explained by the theory.
The direct and converse magnetoelectric (ME) effects in a flexible structure containing a mechanically coupled layers of amorphous ferromagnet FeBSiC and a piezo-copolymer poly(viniledene fluoride trifluoroethylen) (P(VDF-TrFE)) are investigated. The mutual transformation of magnetic and electric fields in the structure arises due to a combination of magnetostriction and piezoelectric effects in the ferromagnetic and piezoelectric layer, respectively. The ME effects were induced by exciting the structure with alternating magnetic fields of 0–100 kHz frequency and 1–5 Oe amplitude, or alternating electric fields of amplitudes up to 500 V/cm in the presence of a constant H field. For the direct ME effect the conversion coefficient reached 7.2 V/(cm·Oe) at a bending resonance frequency of 412 Hz and 44 V/(cm·Oe) at a planar resonance frequency of 25.15 kHz. Increasing the excitation magnetic field at the bending resonance frequency, the nonlinear second harmonic generation with an efficiency of 0.24 V/(cm·Oe2) was observed. For the converse ME effect, the conversion coefficient at the planar resonance frequency was 0.09 G·cm/V. The dependences of the efficiencies for the direct and converse ME transformations on the constant field and the amplitudes of the excitation fields are well explained by theory. These results could be used to develop magnetic and electric field sensors, as well as autonomous energy harvesting sources.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Nonlinear magnetoelectric (ME) effects in a flexible composite planar structure, containing mechanically coupled layers of amorphous FeBSiC ferromagnetic and PVDF piezoelectric polymer have been ...experimentally investigated for the first time•On increasing the excitation field up to h∼7Oe, the structure generated second and third harmonics with efficiencies of ∼25mV/(cm·Oe2) and ∼2.5mV/(cm·Oe3), respectively.•The effects of harmonics generation and magnetic fields mixing arise due to the nonlinear dependence of the ferromagnet’s magnetostriction λ on the bias field H.•The efficiency of the nonlinear processes is proportional to the derivatives of the magnetostriction over magnetic field.•The nonlinear ME effects in the ferromagnet-piezopolymer flexible structures can be used to design high-sensitivity dual ac/dc magnetic field sensors and energy harvesting devices.
Nonlinear magnetoelectric (ME) effects in a flexible composite planar structure, containing mechanically coupled layers of amorphous FeBSiC ferromagnet and PVDF piezoelectric polymer have been experimentally investigated. Under the action of a weak harmonic magnetic field h with frequency f=50–1000Hz and tangential bias magnetic field H=1–80Oe, the structure generated a voltage of the same frequency. The efficiency of linear ME conversion reached 3.4V/(cm·Oe) for the optimum bias field Hm≈15Oe. On increasing the excitation field up to h ∼7Oe, the structure generated second and third harmonics with efficiencies of ∼25mV/(cm·Oe2) and ∼2.5mV/(cm·Oe3), respectively. The amplitudes of the harmonics were not monotonous functions on the bias field H and grew with the increase in the alternating field h. Under the action of two alternating fields with different frequencies f1 and f2, the structure generated ac voltages with frequencies equal to the sum and difference frequencies f1±f2. The efficiency of magnetic fields mixing reached a maximum of ∼30mV/(cm·Oe2) in the absence of the bias field. The effects of harmonics generation and magnetic fields mixing arise due to the nonlinear dependence of the ferromagnet’s magnetostriction λ on the bias field H. The efficiency of the nonlinear processes is proportional to the derivatives of the magnetostriction over magnetic field. The nonlinear ME effects in the ferromagnet-piezopolymer flexible structures can be used to design high-sensitivity dual ac/dc magnetic field sensors and energy harvesting devices.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Magnetoelectric effect in planar Ni-PZT structure with hysteresis is investigated.•Suppression of magnetoelectric hysteresis at high modulation field is observed.•The effect increases measurement ...accuracy of magnetoelectric magnetic field sensors.
Nonlinear magnetoelectric effect in a planar ferromagnetic-piezoelectric composite structure, placed in the constant magnetic field H and harmonic alternating field h, manifests itself in voltage harmonics generation. The hysteresis in the field dependence of magnetostriction of the ferromagnetic layer leads to an ambiguous dependence of the harmonic amplitudes on H. The effect of the hysteresis suppression in the harmonic amplitudes dependences on the field H under increasing amplitude of the excitation field is described in the paper. In a planar structure with Ni and lead zirconate titanate layers, an increase in the field h from 1Oe to 100Oe led to a decrease of the coercive field from 21Oe to 0.4Oe in the field dependence of the first and third voltage harmonics amplitudes. The simulation showed that the effect is caused by a decrease in the relative influence of the constant field on the asymmetry of the ferromagnetic layer magnetostriction loop of the structure with increase of the excitation field. The hysteresis suppression effect will increase the measurement accuracy of the magnetoelectric sensors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Magnetoelectric effects (ME) in ferromagnetic-ferroelectric layered composites arise due to magnetostriction and piezoelectric effect in the ferroic phases and are mediated by mechanical strain. The ...ME coupling strength in such composites could be measured by electrical response to an applied ac magnetic field h and a bias magnetic field H. The coupling, in general, is linear for small ac field amplitudes, but one expects nonlinear ME interactions for high field strengths since the dependence of magnetostriction λ on magnetic fields is nonlinear. Here we report on nonlinear voltage response of a composite of ferromagnetic Metglas and piezoelectric lanthanum gallium tantalate (langatate) subjected to an ac and a bias magnetic fields, resulting in the generation of voltages at harmonics of the frequency of h. The dependences of the ME voltage of the first four harmonics on the magnetic fields for H = 0-20 Oe and h = 0-50 Oe were measured. Up to a hundred harmonics were observed in the voltage versus frequency spectra and was indicative of high nonlinearity of the ME coupling in the multiferroic structure. It is shown that for h smaller than the saturation magnetic field HS for magnetostriction in the ferromagnetic layer, the amplitudes of the ME voltages are proportional to the derivatives of λ with respect to H and show a power-law dependence on the pumping field amplitude An(H) ~ λ(n)(H)hn. We discuss a procedure for estimating the amplitudes of the harmonics for large pumping fields h, on the order of HS. The nonlinear ME effects in the composites are of interest for application in signal processing devices and highly sensitive magnetic field sensors.
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