Self-biased Magnetoelectric Coupling Research Articles

Evidence of self-biased magnetoelectric coupling in eco-friendly (Na0.41K0.09Bi0.5TiO3-Ba0.85Ca0.15Zr0.1Ti0.9O3)-(CoFe2O4) particulate composites

The magnetoelectric (ME) properties of eco-friendly 1-x(0.94Na0.41K0.09Bi0.5TiO3-0.06Ba0.85Ca0.15Zr0.1Ti0.9O3)-x (CoFe2O4) (NKBCZT-CFO) with x = 0, 0.1, 0.2, 0.3 and 0.4 particulate composites were investigated. The X-ray diffraction studies provided evidence for the simultaneous existence of constituent phases (ferroelectric and ferromagnetic) in the composite. The structural and surface morphology analysis of the composite affirmed the homogeneous and densely packed distribution of CFO grains within the NKBCZT matrix. The composite's multiferroic behavior at room temperature was confirmed through the characterization of P vs E and M vs H hysteresis loops. The observed values of remnant polarization (Pr) and coercive field (Ec) are 26.7 μC/cm2 and 35.5 kV/cm, respectively, for 10 mol% of CFO. The increase in CFO content resulted in a decrease in the ferroelectric properties, possibly due to the conductive behaviour exhibited by CFO, and correlated with leakage current measurement. For the composite containing 40 mol% of CFO, the estimated values of remanent (Mr), saturation (Ms) magnetization, coercive field (Hc), and magnetic moment (µB) are 2.35 emu/g, 21.85 emu/g, 104.2 Oe, and 0.86 µB, respectively. The non-Debye type dielectric relaxation processes have been observed in the composites, and the electron hopping mechanism resulted in a higher dielectric constant (εʹ). Enhancement in relaxor nature had been observed through Vogel-Fulcher analysis with CFO content. The evidence of ME coupling was revealed through the direct ME voltage coefficient (αME) and magnetocapacitance (MC) measurement. The observed maximum value of MC measured at 1 kHz for the 20 mol% CFO is ∼5.6 %. Self-biased ME coupling (non-zero αME at HDC = 0 Oe) was observed in 20 and 30 mol% of CFO composite. The highest measured value of αME for 20 and 30 mol% CFO is 3.63 mV/cm.Oe and 4.09 mV/cm.Oe at HDC = 0 Oe respectively. The strong ME interaction and significant value of self-biased ME αME suggest that these composites can be explored for magnetic sensor and ME memory device applications.

Exchange bias mediated self-biased magnetoelectric coupling in Co–BaTiO3 composites

The magnetoelectric composites of ferromagnetic cobalt (Co) with various morphologies and ferroelectric BaTiO3 (BTO).

Self-biased magnetoelectric coupling effect in the layered La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 multiferroic heterostructure

The experimental observation and analysis of self-biased magnetoelectric (ME) coupling effect in the layered La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 (LSMO/BTO/LSMO) multiferroic heterostructure were reported, and the epitaxial layered LSMO/BTO/LSMO heterostructure was grown on (001) oriented LaAlO3 (LAO) single crystal substrate by using pulsed laser deposition technique. The microstructure, ferromagnetic and ferroelectric properties were studied. The exchange bias effect in the LSMO/LAO interface and the compressive strain gradient field in the heterostructure induced by lattice mismatch resulted in a built-in magnetic bias field (Hbias) in the LSMO layer, which provided limited ME coupling effect at zero applied DC bias magnetic field. It may potentially be used to micro-nano devices especially for multiple state memories.

Enhanced Self-Biased Magnetoelectric Coupling in Laser-Annealed Pb(Zr,Ti)O3 Thick Film Deposited on Ni Foil.

Enhanced and self-biased magnetoelectric (ME) coupling is demonstrated in a laminate heterostructure comprising 4 μm-thick Pb(Zr,Ti)O3 (PZT) film deposited on 50 μm-thick flexible nickel (Ni) foil. A unique fabrication approach, combining room temperature deposition of PZT film by granule spray in vacuum (GSV) process and localized thermal treatment of the film by laser radiation, is utilized. This approach addresses the challenges in integrating ceramic films on metal substrates, which is often limited by the interfacial chemical reactions occurring at high processing temperatures. Laser-induced crystallinity improvement in the PZT thick film led to enhanced dielectric, ferroelectric, and magnetoelectric properties of the PZT/Ni composite. A high self-biased ME response on the order of 3.15 V/cm·Oe was obtained from the laser-annealed PZT/Ni film heterostructure. This value corresponds to a ∼2000% increment from the ME response (0.16 V/cm·Oe) measured from the as-deposited PZT/Ni sample. This result is also one of the highest reported values among similar ME composite systems. The tunability of self-biased ME coupling in PZT/Ni composite has been found to be related to the demagnetization field in Ni, strain mismatch between PZT and Ni, and flexural moment of the laminate structure. The phase-field model provides quantitative insight into these factors and illustrates their contributions toward the observed self-biased ME response. The results present a viable pathway toward designing and integrating ME components for a new generation of miniaturized tunable electronic devices.

A flexible multiferroic composite with high self-biased magnetoelectric coupling

Polymer-matrix multiferroic composites with self-biased magnetoelectric (ME) coupling hold promises in flexible energy harvester, magnetic field sensors and actuators, etc. Using CoFe2O4 (CFO) nanoparticles and multi-walled carbon nanotubes (CNTs) as fillers to the polyvinylidene fluoride (PVDF) matrix, piezomagnetic films (CFO-CNT-PVDF, also named as M layers) with different volume fractions of CFO and a fixed percentage of CNTs are obtained, which also serve as the electrode. By employing the layer of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE), named as P layer) sandwiched between the two conductive layers of CFO-CNT-PVDF, and followed by hot-pressing, three-layered multiferroic composite CFO-CNT-PVDF/P(VDF-TrFE)/CFO-CNT-PVDF (named as M/P/M) are prepared. The ME coupling increases with the volume fraction of CFO nanoparticles. The maximum self-biased and peak values of ME coefficient (αME) reach 16.7 mV cm−1 Oe−1 and 25.8 mV cm−1 Oe−1, respectively. Measurements on the relationship between the magnetostriction and static magnetic field (Hs) are performed for the CFO-CNT-PVDF films with different volume fraction of CFO. Based on the equivalent circuit model, the self-biased and peak values of αME are calculated for the ME composites, which fit well with the experimental data. The results imply that it is the high piezomagnetic coefficient, as well as the remnant magnetization of the M layer, contributes to the observed strong self-biased ME coupling for the CFO-CNT-PVDF/P(VDF-TrFE)/CFO-CNT-PVDF composite. Since the mechanical flexibility is also of great importance regarding the practical device applications, the stress-strain behavior for the CFO-CNT-PVDF layers is studied. With the volume fraction of CFO increases, both fracture strength (σf) and fracture strain (εf) decrease. The results offer a guideline for selecting proper ME composites on specified device applications.

Large self-biased and multi-peak magnetoelectric coupling in transducer of Pb(Zr,Ti)O3 plates and H-type magnetization-graded ferromagnetic fork

This paper develops a self-biased magnetoelectric (ME) composite Metglas/H-type-FeNi/PZT (MHFP) of H-type magnetization-graded Metglas/H-type-FeNi fork and piezoelectric Pb(Zr,Ti)O3 (PZT) plate. By using the magnetization-graded magnetostrictive layer and symmetrical H-type structure, giant self-biased ME coupling and multi-peak phenomenon are observed. The zero-biased ME voltage coefficient of MHFP composite reaches ∼63.8 V/cm Oe, which is ∼37.5 times higher than that of traditional FeNi/PZT laminate. The output ME voltage has a good near linear relation with Hac and is determined to be ∼5.1 V/Oe and ∼10.6 mV/Oe at ∼65 kHz and 1 kHz, respectively. These indicate that the proposed composite show promising applications for ME transducers and high-sensitivity self-biased magnetic sensors.

Stress-induced self-biasing of magnetoelectric coupling in embedded Ni/PZT/FeNi composite

In this study, a self-biased magnetoelectric (ME) composite is designed without employing the epoxy and magnetization-graded materials. The composite is referred to as the three-phases-embedded one, consisting of a PZT ring with an inner disc of Ni50Fe50 and an outer ring of Ni via hard contact (Ni/PZT/FeNi composite). A large self-biased ME response and apparent hysteresis behavior are observed in the composites. Stress analysis and finite element simulation are carried out to reveal the underlying mechanism of the self-biased ME coupling and the magnetic-elastic-electric coupling of the embedded composites. The results indicate that the assembly stress induces magnetization of Ni at zero bias, and renders the self-biased ME coupling effect for the embedded Ni/PZT/FeNi composite.

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.

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.

Giant self-biased magnetoelectric coupling in co-fired textured layered composites

Co-fired magnetostrictive/piezoelectric/magnetostrictive laminate structure with silver inner electrode was synthesized and characterized. We demonstrate integration of textured piezoelectric microstructure with the cost-effective low-temperature co-fired layered structure to achieve strong magnetoelectric coupling. Using the co-fired composite, a strategy was developed based upon the hysteretic response of nickel-copper-zinc ferrite magnetostrictive materials to achieve peak magnetoelectric response at zero DC bias, referred as self-biased magnetoelectric response. Fundamental understanding of self-bias phenomenon in composites with single phase magnetic material was investigated by quantifying the magnetization and piezomagnetic changes with applied DC field. We delineate the contribution arising from the interfacial strain and inherent magnetic hysteretic behavior of copper modified nickel-zinc ferrite towards self-bias response.