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

在这个项目中，我们建议建立一个高灵敏度的多频电子自旋共振（扭矩检测）光谱仪，并使用它来研究半金属铁磁体和内嵌金属富勒烯的磁各向异性性质。磁各向异性总是与其他基本性质并行不悖，例如过渡金属氧化物、金属合金或各种分子磁体（MM）中的电子相关性，包括内嵌金属富勒烯（EMF）。因此，磁各向异性的研究提供了不同材料的内在属性的直接见解。这可以进一步导致观察到新的现象，或改进已知的性能，使材料可以找到技术应用。在半金属铁磁体的情况下，磁各向异性以及诸如阻尼的动态性质负责磁化的稳定性和切换磁状态的能力。电磁场中的磁各向异性，表现出单分子磁体行为，可以产生零场弛豫时间达到几个小时的长寿命量子态。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，以满足构建设备的要求;分子磁体，例如EMF，其中每个分子具有纳米尺寸，当沉积在基底上作为单层时特别有趣。为了全面了解磁特性，必须在各种频率、磁场以及样品与所施加磁场之间的不同角度下测量上述化合物的ESR。这在标准ESR设置中并不总是可能的，这是由于缺乏灵敏度，或者由于磁场的频率、强度和方向的限制。悬臂梁具有极高的灵敏度，几乎与微波频率和磁场无关，并且相对容易对准它们。这使我们有信心，所构建的悬臂检测ESR设置将能够探索静态和动态磁各向异性性质的半金属铁磁体和内嵌金属富勒烯。

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.