• 한국자기학회지
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• 제7권6호
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• pp.285-292
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• 1997

Cobalt ferrite와 Pb(Zr, Ti) $O_{3}$ 복합체를 고상 반응법으로 제조하여, magnetoelectric 효과를 조사하였다. 소결 시간과 cobalt ferrite의 부피비가 증가함에 따라 magnetoelectric 전압 계수의 최대값이 증가하였다. 한편, 이 최댜값을 나타내는 자기장은 소결 시간 증가에 따라 낮은 쪽으로, cobalt ferrite 부피 증가에 따라 높은 쪽으로 이동하였다. 이러한 현상들은 각 상의 입자 크기 변화와 이에 따른 응력 전달 변화, 자화 및 분극 용이도로 설명되었다. 비화학당량 조성인 $Co_{1.02}$F $e_{1.98}$ $O_{4}$를 사용하여, 이제까지 발표된 최대 효과보다 약 30% 높은 0.174 V/cm Oe 의 magnetoelectric 전압 계수 값을 얻었다.얻었다.

• The Korean Journal of Ceramics
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• 제4권2호
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• pp.83-89
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• 1998

The structure refinements and the electrical and magnetoelectric measurements were performed for BIT.1BF and BIT.2BT. The tetragonal distortion of the ab plane became lessened with the addition of $4BiFeO_3 into Bi_4Ti_3O_{12}$ significantly. However, the tilting of the outer-oxygen octahedra of the perovskite unit and the elongatin of the $(Bi_2O_2)^{2+}$ layers became more pronounced. For the both phases, the bariations of dielectric properties and electrical conductivities at high temperatures showed that the ferroelectic I-rerroelectric II phase transition existed before reaching the Curie temperature. The electrical conductivity became higher with the increase of $Fe^{3+}$ ions, implying that the electron transfer increased correspondingly. The magnetoelectric effect was observed linear up to ~8 kOe, which was stronger in BIT.1BF than BIT.2BF. This behavior indicates that the distortion of the ab plane may affect the induced polarization as well as magnetic moment.

• 한국세라믹학회지
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• 제44권6호
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• pp.308-312
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• 2007

Ferroelectric, magnetic, and magnetoelectric effects for lanthanum modified $BiFeO_3-PbTiO_3$ ceramics have been investigated. The data show that magnetoelectric polarization coefficient, ${\alpha}_p$ is due to a linear coupling between polarization and magnetization, and that ${\alpha}_p$ is independent of dc magnetic bias and ac magnetic field. The values of ${\alpha}_p$ and magnetic induced susceptibility for lanthanum modified $BiFeO_3-PbTiO_3$ ceramics are much larger than those of single $BiFeO_3$ crystal. We believe that the magnetoelectric effect is significantly enhanced by breaking of the cycloidal spin state of a long-period spiral spin structure due to randomly distributed charged imperfections.

• 센서학회지
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• 제22권6호
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• pp.379-386
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• 2013

The influences of the load resistance $R_L$ on the magnetoelectric (ME) characteristics of $NiZnFe_2O_4+PZT$ composite were investigated in the non-resonance frequency range. The ME coefficient peak increases with increasing $R_L$, but the frequency indicating the ME coefficient peak decreases with increasing $R_L$. The maximum output power peak is approximately $9.3{\times}10^{-10}mW/Oe$ near $R_L=3.3M{\Omega}$ at f=280 Hz, and the ME coefficient seems to be saturated at $R_L>20M{\Omega}$. This frequency shift effect of $R_L$ shows that the frequency range for an ME sensor application can be modulated with the appropriate value of $R_L$. The ME output voltage has a good linear response to the ac field Hac and shows fair stability over a range of temperatures. The measured non-linearity of this sample is approximately 0.8%. This sample will allow for a low-strength magnetic ac-field sensor. The result from this sample will serve as basic data for a signal-processing circuit system.

• Advanced Composite Materials
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• 제18권2호
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• pp.153-166
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• 2009

A matrix method for evaluating effective electro-magneto-thermo-elastic properties of a generally anisotropic multilayered composite is presented. Physical variables are categorized into two groups: one that satisfies the continuity across the interface between layers and another that satisfies an average inter-layer compatibility (which is also exact). The coupled electro-magneto-thermo-elastic constitutive equation is accordingly reassembled into submatrices, which leads to the derivation of concise and exact matrix expressions for effective properties of a multilayered composite having the coupled physical effects. Comparing the results for a purely elastic multiplayer with those from other theoretical approaches validates the developed method. Examples are given for a PZT-graphite/epoxy composite and a $BaTiO_3-CoFe_2O_4$ multiplayer which exhibit piezo-thermoelastic and magnetoelectric properties, respectively. The result shows how a strong magnetoelectric effect can be achieved by combining piezoelectric and piezomagnetic materials in a multilayered structure. The magnetoelectric coefficient of the $BaTiO_3-CoFe_2O_4$ multiplayer is compared with those for fibrous and particulate composites fabricated with the same constituents.

• Journal of Magnetics
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• 제20권4호
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• pp.347-352
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• 2015

The magnetoelectric (ME) characteristics for Terfenol-D/PZT laminate composite dependence on bias magnetic field is investigated. At low frequency, ME response is determined by the piezomagnetic coefficient $d_{33,m}$ and the elastic compliance $s_{33}^H$ of magnetostrictive material, $d_{33,m}$ and $s_{33}^H$ for Terfenol-D are inherently nonlinear and dependent on $H_{dc}$, leading to the influence of $H_{dc}$ on low-frequency ME voltage coefficient. At resonance, the mechanical quality factor $Q_m$ dependences on $H_{dc}$ results in the differences between the low-frequency and resonant ME voltage coefficient with $H_{dc}$. In terms of ${\Delta}E$ effect, the resonant frequency shift is derived with respect to the bias magnetic field. Considering the nonlinear effect of magnetostrictive material and $Q_m$ dependence on $H_{dc}$c, it predicts the low-frequency and resonant ME voltage coefficients as a function of the dc bias magnetic field. A good agreement between the theoretical results and experimental data is obtained and it is found that ME characteristics dependence on $H_{dc}$ are mainly influenced by the nonlinear effect of magnetostrictive material.

• 한국재료학회지
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• 제15권2호
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• pp.121-125
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• 2005

Magnetoelectric (ME) effects for lanthanum modified $BiFeO_3-PbTiO_3\;(BE-_xPT)$ solid solutions have been investigated. The value of magnetoelectric polarization coefficient, up is 10 times greater than that of $Cr_2O_3$. The results also show that up is due to a linear coupling between polarization and magnetization, and that up is independent of do magnetic bias and ac magnetic field. The ME effect is believed to be significantly enhanced due to breaking of the cycloidal spin state of a long-period spiral spin structure, via randomly distributed charged imperfections.

• Journal of Magnetics
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• 제16권4호
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• pp.461-465
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• 2011

Traditional magnetostrictive/piezoelectric laminate composites are generally in the regular geometries such as rectangles or disks. To explore properties of the irregular geometry magnetostrictive/piezoelectric transducer in the fundamental resonant frequency, a step dumb-bell shaped Magnetoelectric (ME) transducer is presented in this study. Both analytical and experimental investigations are carried out for the dumb-bell shaped transducer in the fundamental frequency. Comparing with the traditional rectangular transducer, the theory shows the resonant frequency of dumb-bell shaped transducer is reduced 31%, and the experiment gives the result of that is 37% which is independent of dc magnetic fields. The ratio of magnetoelectric voltage coefficient (MEVC) between the dumb-bell shaped and rectangular shaped transducers in theory is 66% comparing with that of in experiment is varying from 140% to 33% when the dc field is increased from 0 Oe to 118 Oe.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1696-1697
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• 2011

최근들어 멀티 페로익스(multiferroics)재료를 이용하여 자계(magnetic field)하에서 전기적현상(polarization)을 유기시키는 재료에 대한 관심이 폭발적으로 증가되고 있다. 이는 megnetoelectric 효과(ME 효과)를 이용하는 방법으로, 자기 및 전류센서에 응용함을 위해 크게 각광받고 있으며, 본 연구에서는 자계내에서 자성재료-압전재료의 다층 구조 캔틸레버의 구현을 통해 전기적인 신호로의 변화를 통해 전류 및 자기 센서로의 가능성에 대한 연구를 진행하였다.

• 한국전기전자재료학회논문지
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• 제28권2호
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• pp.92-98
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• 2015

The magnetoelectric characteristics on layered Ni-PZT-Ni, Co, Fe composites by epoxy bonding for magnetic field sensor were investigated in the low-frequency range. The ME coefficient of Ni-PZT-Ni, Ni-PZT-Co and Ni-PZT-Fe composites reaches a maximum of $200mV/cm{\cdot}Oe$ at $H_{dc}=110$ Oe, $106mV/cm{\cdot}Oe$ at $H_{dc}=90$ Oe and $87mV/cm{\cdot}Oe$ at $H_{dc}=160$ Oe, respectively. A trend of ME charateristics on Ni-PZT-Co, Ni-PZT-Fe composites was similar to that of Ni-PZT-Ni composites. The ME output voltage shows linearly proportional to ac field $H_{ac}$ and is about 0~150 mV at $H_{ac}$=0~7 Oe and f=110 Hz in the typical Ni-PZT-Ni sample. The frequency shift effect due to the load resistance $R_L$ shows that the frequency range for magnetic field sensor application can be modulated with appropriate load resistance $R_L$. This sample will allow for a low-magnetic ac field sensor in the low-frequency (near f=110 Hz).