Cantilever (torque) detected multifrequency electron spin resonance spectroscopy of halfmetallic compounds and endohedral metallofullerenes

本项目拟建立高灵敏度多频悬臂式（转矩检测）电子自旋共振（ESR）光谱仪，用于半金属铁磁体和内嵌金属富勒烯的磁各向异性研究。磁性各向异性总是与其他基本性质密切相关，例如过渡金属氧化物、金属合金或各种分子磁体（MM）（包括内嵌金属富勒烯（EMF））中的电子相关性。因此，磁各向异性的研究为了解不同材料的内在特性提供了直接的途径。这可以进一步导致对新现象的观察，或对已知性质的改进，从而使材料可以找到技术应用。在半金属铁磁体的情况下，磁各向异性以及阻尼等动态特性负责磁化的稳定性和切换磁状态的能力。电磁场的磁各向异性，表现出单分子的磁性行为，可以产生长寿命的量子态，零场弛豫时间达到几个小时。对于这些材料，样品的尺寸起着至关重要的作用：有希望用于自旋电子学应用的金属合金必须制成薄的纳米尺寸的薄膜，以满足构建器件的要求；分子磁体，如电磁场，其中每个分子都有纳米大小，当作为单层沉积在衬底上时特别有趣。为了充分了解磁性，必须测量上述化合物在不同频率、不同磁场以及样品与外加磁场之间不同角度下的ESR。由于缺乏灵敏度，或者由于磁场的频率、强度和方向的限制，在标准ESR设置中并不总是能够做到这一点。悬臂梁具有极高的灵敏度，几乎与微波频率和磁场无关，并且相对容易对准。这使我们相信，构建的悬臂检测ESR装置将能够探索半金属铁磁体和内嵌金属富勒烯的静态和动态磁各向异性。

In this project we propose to build a highly sensitive multifrequency cantilever-based (torque-detected) electron spin resonance (ESR) spectrometer, and to use it for studies of magnetic anisotropic properties of halfmetallic ferromagnets and endohedral metallofullerenes. Magnetic anisotropy always goes side by side with other fundamental properties, such as electronic correlations in transition metal oxides, in the metallic alloys, or in all kinds of molecular magnets (MM), including endohedral metallofullerenes (EMF). Therefore the study of the magnetic anisotropy provides direct insights into the intrinsic properties of different materials. This can further lead to the observation of new phenomena, or to the improvement of the known properties, so that the material can find technological applications. In the case of halfmetallic ferromagnets magnetic anisotropy as well as such dynamic property as a damping are responsible for the stability of the magnetization and for the ability to switch the magnetic state. Magnetic anisotropy in EMFs, which exhibit single molecular magnet behavior, could yield long living quantum states with zero-field relaxation times reaching several hours. For these materials the size of the sample plays a crucial role: metallic alloys promising for spintronics application has to be made as a thin, nm-size, films, in order to fulfill the requirements for building a device; molecular magnets, such as EMFs, where each molecule has a nanometer size, are especially interesting when deposited on the substrate as single layer. In order to have full access to the magnetic properties it is essential to measure ESR on above mentioned compounds at various frequencies, magnetic fields and at different angles between the sample and the applied magnetic field. This is not always possible in the standard ESR setups, due to a lack of sensitivity, or due to the restriction in frequency, strength and orientation of magnetic field. Cantilevers have an extremely high sensitivity, which is almost independent of the microwave frequency and magnetic field, and it is relatively easy to align them. This makes us confident that the constructed cantilever detected ESR setup will enable to explore static and dynamic magnetic anisotropic properties of halfmetallic ferromagnets and endohedral metallofullerenes.