Exploring new functionalities of magnetic materials utilizing nanoplasmonics and multiferroics

点击翻译按钮获取中文摘要

The purpose of this proposal is to explore new functionalities of magnetic materials utilizing nanoplasmonics and multiferroics. In particular, we are interested in developing new ways to control magnetism optically or electrically.*** In the first part of the research, we will investigate the interaction between light and magnetism, which is of utmost importance in terms of fundamental science and technological applications. A specific goal is the ultrafast light control of magnetism. The strength of the interaction of light with a magnetic medium, however, is very weak, and this weak interaction has been the main challenge in optically probing or controlling magnetism. In order to overcome this drawback, we will exploit magneto-plasmonics, which combines magnetic and plasmonic functionalities. In our previous studies, we observed that the incorporation of noble-metal nanoparticles in ferromagnetic films significantly enhances magneto-optical (MO) effect. We will conduct systematic studies on the influence of plasmon resonance on MO effect, and develop a better understanding of the underlying mechanism of the enhanced MO activities. We will also study the ultrafast magnetism triggered by optically excited high energy electrons. The questions to be answered are: can we enhance the optical generation of hot electrons via localized surface plasmon resonance? If so, how effectively can we manipulate the hot-electron induced ultrafast magnetic process? Another project is to generate large wavenumber spin waves using ultrafast optical excitation. It is known that the spin wavenumber is determined by the spatial intensity distribution of the pumping light. We will be able to reduce the pump spot size to the nanoscale by using near-field optics. Higher spin wavenumbers can also be generated by using the localized surface plasmon resonance, in which the spatial intensity distribution is determined by the geometries of the nanoparticles.*** The second part of the research is to explore the opportunity of electric-field control of magnetism utilizing magnetoelectric multiferroics, which enables the coupling between magnetic and ferroelectric orders. However, room temperature multiferroics are very rare, with BiFeO3 (BFO) being an exception. Its drawback is that it has a very weak magnetic moment. Recently, it was found that a double perovskite material Bi2FeCrO6 (BFCO) has ferroelectricity similar to BFO with the added benefit of a strong magnetic moment. Our main goal is to answer the question whether BFCO can provide a new avenue for electric-field switching of magnetism. We will also investigate the electric-field triggered magnetization dynamics in gated BFCO thin films. Considering that the electric-field control of magnetism enabled by multiferroics has the potential to revolutionize today's electronics technology, the outcome of the proposed research will be significant.