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

• Applicant: Dr. Alexey Alfonsov, Ph.D.
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2016 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 321732198

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.

• DFG Programme: Research Grants