• Coupled systems mechanics
• /
• 제10권2호
• /
• pp.185-198
• /
• 2021

An analytical model is consider to scrutinize axisymmetric wave propagation in multiferroic hollow cylinder with rotating and initial stressed forces, where a piezomagnetic (PM) material layer is bonded to a piezoelectric (PE) cylinder together by Linear elastic materials with voids. Both distinct material combos are taken into account. Three displacement potential functions are introduced to uncouple the equations of motion, electric and magnetic induction. The numerical calculations are carried out for the non-dimensional frequency by fixing wave number and thickness. The arrived outputs are plotted as the dispersion curves for different layers. The results obtained in this paper can offer significance to the application of PE/PM composite hollow cylinder via LEMV and CFRP layers for the acoustic wave and microwave technologies.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
• /
• pp.318-319
• /
• 2008

In this article, magnetic properties of multiferroic bi-layer $BiFeO_3$ (BFO)/$BaTiO_3$ (BTO) thin films were studied. It was found that the magnetization increased by the insertion of BTO buffer layer even though the interfacial stress was slightly relaxed, which indicated a coupling between the ferroelectric and ferromagnetic orders. Furthermore, with slightly increase of BFO film thickness, both BFO and BFO/BTO bi-layer films showed anisotropic magnetic properties with higher in-plane magnetization than the values measured out-of-plane. These are attributable to strain constraint effect at the interface.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2012년도 자성 및 자성재료 국제학술대회
• /
• pp.170-171
• /
• 2012

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
• /
• pp.147-147
• /
• 2013

Multiferroic material $BiFeO_3$ (BFO) is a typical multiferroic material with a room-temperature magnetoelectric coupling in view of high magnetic- and ferroelectric-ordering temperatures (Neel temperature $T_N$ ~ 647 K and Curie temperature TC ~1,103 K). Rare-earth ion substitution at the Bi sites is very interesting, which induces suppressed volatility of the Bi ion and improved ferroelectric properties. At the same time, the Fe-site substitution with magnetic ions is also attracting, since the enhanced ferromagnetism was reported. In this study, BFO, $Bi_{0.9}Dy_{0.1}FeO_3$ (BDFO), $BiFe_{0.97}Co_{0.03}O_3$ (BFCO) and $Bi_{0.9}Dy_{0.1}Fe_{0.97}Co_{0.03}O_3 $ (BDFCO) compounds were prepared by conventional solid-state reaction and wet-mixing method. High-purity $Bi_2O_3$, $Dy_2O_3$, $Fe_2O_3$ and $Co_3O_4$ powders with the stoichiometric proportions were mixed, and calcined at $500^{\circ}C$ for 24 h. The samples were immediately put into an oven, which was heated up to 800oC and sintered in air for 1 h. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The field-dependent magnetization measurements were performed with a vibrating-sample magnetometer. The electric polarization was measured at room temperature by using a standard ferroelectric tester (RT66B, Radiant Technologies). Dy and Co co-doping at the Bi and the Fe sites induce the enhancement of both magnetic and ferroelectric properties of $BiFeO_3$.

• 한국분말재료학회지
• /
• 제14권3호
• /
• pp.180-184
• /
• 2007

The material design and synthesis are of important to modem science and technology. Here, we report the synthesis of multifunctional nanomaterials with different properties: feroelecties $YMnO_3$ and multiferroic materials such as $CoFe_2O_4-YMnO_3,\;Fe_3O_4-YMnO_3,\;CoFe_2O_4-Cd_{0.85}Zn_{0.15}S,\;and\;Fe_3O_4-Cd_{0.85}Zn_{0.15}S$ nano-composites by using a chemical synthesis process. These results provide a simple and convenient synthesis process to produce multifunctional nanocomposites.

• Journal of Magnetics
• /
• 제16권1호
• /
• pp.19-22
• /
• 2011

[ $BiFeO_3$ ]is a multiferroic material that attracts attentions of many research groups due to its potential as being ferroelectric and ferromagnetic above room temperature. We have prepared both undoped- and Mn-doped $BiFeO_3$ by sol-gel auto-ignition method. Doping of Mn has resulted in decreasing grain size from 60 to 32 nm. X-ray diffraction data show that the samples are pure and single-phase. Infrared measurements on $BiFeO_3$ and Mn-doped $BiFeO_3$ revealed intrinsic stretching vibrations of tetrahedral sites of $Fe^{3+}$-O and of octahedral $Bi^{3+}$-O as well. On the other hand, as the Mn concentration increases, the magnetic moment of $BiFeO_3$ increases. It gives some suggestions in manipulating structural and magnetic properties of $BiFeO_3$ by doping Mn.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2007년도 The 1st International Symposium on Advanced Magnetic Materials
• /
• pp.282.1-282.1
• /
• 2007

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 하계학술대회 논문집
• /
• pp.175-175
• /
• 2009

최근 전자 소자의 소형화 집적화에 따른 대응 방안으로 한 개의 소자에 두가지 이상의 물리적 특성을 갖는 다기능성 소재의 개발에 많은 연구가 진행되고 있다. 다강체는 강유전성 (ferroelectricty ), 강자성 (ferromagnetism), 강탄성 (ferroelasticity) 중에서 두 개 이상의 현상을 나타내는 재료로, 이중에서도 특히 강유전성과 강자성을 동시에 나타내는 다강체가 학계 및 산업계로부터 집중적인 관심을 받으면서 최근 이 분야 연구가 국내 외적으로 매우 활발하게 이루어지고 있다. 이는 다강체를 이용하면 기존의 강유전 현상을 이용한 메모리소자인 FRAM이나 차세대 메모리소자로 주목을 받고 있는 MRAM을 결합한 새로운 방식의 메모리소자의 탄생이 가능할 수도 있기 때문이다. 즉, 일부 다강체가 나타내는 magnetoelectric (ME) 현상을 이용하면 자기적으로 신호를 인가하여 전기신호로 데이터를 저장하거나 또는 전기적으로 신호를 인가하여 자기적으로 데이터를 저장하는 것이 가능해지기 때문이다. 이 연구에서는 다강체 특성을 가지는 $Fe/BaTiO_3$ 이중박막을 IBSD(Ion Beam Sputter Deposition)을 이용하여 (111)Pt/Ti/$SiO_2/Si$ 기판에 증착을 하여 구조적, 전기적, 자기적 특성을 토론할 것이다.

• 한국전기전자재료학회논문지
• /
• 제23권12호
• /
• pp.949-955
• /
• 2010

Nd and Ti co-doped bismuth ferrite $(Bi_{1-x}Nd_x)(Fe_{1-y}Ti_y)O_3$ (x, y = 0, 0.05, 0.1, 0.2) ceramics and thin films were synthesized through the conventional mixed-oxide process and pulsed laser deposition (PLD), respectively. Nd and Ti co-doping effect was examined with emphasis on how these impurities affect phase formation behavior as there could be the improvement in leakage current problems often associated with multiferroic $BiFeO_3$ (BFO) thin films. The lattice constants of BFO ceramics decreased with Nd doping concentration up to 10mol%, while they further decreased with Nd and Ti co-doping to about 20%. BFO thin films obtained by the PLD process revealed random polycrystalline structure. Similar to bulk BFO ceramic, Nd and Ti co-doping effectively suppressed the formation of unwanted secondary phase and thus stabilized the perovskite phase in BFO thin films.

• 한국전기전자재료학회논문지
• /
• 제24권11호
• /
• pp.895-899
• /
• 2011

Multiferroic BFO/PZT(5/95) multilayer films were fabricated by spin-coating method on the Pt/Ti/$SiO_2$/Si substrate alternately using BFO and PZT(9/95) alkoxide solutions. The structural and dielectric properties were investigated with variation of the solvent and the number of coatings. All films showed the typical XRD patterns of the perovskite polycrystalline structure without presence of the second phase such as $Bi_2Fe_4O_3$. BFO/PZT multilayer thin films showed the typical dielectric relaxation properties with increase an applied frequency. The average thickness of 6-coated BFO/PZT multilayer film was about 600 nm. The dielectric properties such as dielectric constant, dielectric loss and remnant polarization were superior to those of single composition BFO film, and those values for BFO/PZT multilayer film were 1199, 0.23% and 12 ${\mu}C/cm^2$.