From Multiferroic Composite Oxides to Composite Thin Films Fabrication

总结这项研究的目的是生产电子传感器，这反过来将有助于培育以多铁性为基础的新的加拿大电子工业。多铁性材料，或称多铁性材料(MF)，包括陶瓷化合物及其在适当衬底上的薄膜，同时显示出电子和磁性。我们寻找至少表现出两种铁性行为的材料，例如铁磁性(永久磁矩)和铁电性(自发电极化)。有几种单相氧化物表现出多铁性行为；然而，这些行为在室温下观察不到，这是任何应用目的的重要要求，例如可以电写和磁读的存储器件。对复合材料(包含两个或两个以上化合物的材料)的新研究表明，可以创造一个环境，其中复合材料中的磁相影响复合材料中的电相，反之亦然；这被称为磁电效应(ME)。CoFe2O4-BaTiO3、PZT(PZT)、铁氧体和BaTiO3等化合物在陶瓷和衬底薄膜中都表现出MF/Me效应，目前这些复合材料是通过在铁电材料中引入磁性颗粒或磁性纳米纤维或通过制备复合材料的薄膜来形成两相层而形成的。我们建议制造核壳，其中粒子的核心由磁性材料的纳米颗粒组成，外壳(核心表面的厚层)由铁电材料组成。这一过程可以通过湿化学技术和控制合成因素来实现。使用这种方法，我们预计可以制造出纳米复合材料形状，并在两相之间创建一个连贯的界面。我们正计划利用这些复合纳米粒子来制备高密度陶瓷片，这是薄膜制备所必需的，如CoFe2O4/BiFeO3，La2/3Sr1/3MnO3/Pb(ZrTi)O3和新的四方钨青铜。我们还在继续寻找新的单一多铁材料化合物。我们关注的是具有对铁电性观测很重要的结构的材料。它还应包含用于观察铁磁性的高磁矩元素(过渡金属或稀土)。我们的计划是使用脉冲激光沉积或射频溅射技术来生产这些化合物的薄膜，在我的实验室中表征它们的物理、电子和磁性，并研究它们可能的应用。最终的结果将是使用多铁材料(MF)生产电子传感器。

SUMMARYThe purpose of this research is to produce electronic sensors which in turn will help foster a new Canadian electronic industry based on multiferroics. Multiferroic materials, or multiferroics (MF), which include ceramic compounds and their thin films on an appropriate substrate, show both electronic and magnetic properties. We look for materials that show at least two ferroic behaviors such as ferromagnetism (permanent magnetic moment) and ferroelectricity (spontaneous electric polarization). There are several single-phase oxides that show multiferroic behaviors; however, these behaviors are not observed at room temperature, which is an important requirement for any application purposes such as memory devices that can be electrically written and magnetically read.New research on composite materials (material containing two or more compounds) indicates that one can create an environment where the magnetic phase in the composite affect electric phase in the composite and vise-versa; this is called the magnetoelectric effect (ME). Scientist have been focusing on ceramic composites of several compounds such as CoFe2O4-BaTiO3, Pb(ZrTi)O3 (PZT), Ferrite and BaTiO3 which show MF/Me effects both in ceramics and thin films on substrates.Currently these composite materials are formed by introducing magnetic particles or magnetic nanofibers into ferroelectric materials or creating two-phase layers by fabricating thin film of composites. We propose to fabricate core-shells where the core of the particle is made up of nanoparticles of magnetic materials and the shell (a thick layer on the surface of the core) is made up of ferroelectric materials. This process can be achieved by a wet chemical technique and by controlling the synthesizing factors. Using this method, we anticipate fabricating nanocomposite shapes and create a coherent interface between the two phases. We are planning to use these composite nanoparticles to fabricate high density ceramic tablets, essential for film fabrication, such as CoFe2O4/BiFeO3, La2/3Sr1/3MnO3/ Pb(ZrTi)O3 and new tetragonal tungsten Bronzes.We also continue our quest to find new single multiferroic material compounds. We are focusing on materials with a structure which is important for the observation of ferroelectricity. It should also contain elements with high magnetic moments (transition metal or rare earth) for observing ferromagnetism. Our plan is to produce the thin films of these compounds using pulse laser deposition or RF-sputtering techniques, to characterize their physical, electronic and magnetic properties in my lab, and to examine their possible applications. The ultimate outcome will be the production of electronic sensors using multiferroic materials (MF).