Open Access

Franziska Breitner

• In this thesis, a combined FIB-SEM set up is utilized in order to investigate several members of the honeycomb Kitaev magnets, including α-RuCl3, Na2IrO3 and β-Li2IrO3, as well as the kagome magnetic metals CrRhAs and CrNiAs. An in depth analysis of the structure and electrical transport behaviour of Na2IrO3 reveals structural domain walls with different degrees of Na deficiency resulting in metallic resistivity down to 2K for a sample with a Na/Ir ratio of 1.1, indicating a local tuning across the metal-to-insulator transition. For α-RuCl3, thermal annealing leads to the formation of RuO2, the influence of which on the low temperature heat capacity as well as magnetic susceptibility and electrical resistivity is described here. FIB microsectioning is utilized for thinning a β-Li2IrO3 single crystal down to ∼1µm for future experiments looking into the dynamics of the systems magnetic and structural ordering parameters, such as dissipative pump-probe spectroscopy. The firstIn this thesis, a combined FIB-SEM set up is utilized in order to investigate several members of the honeycomb Kitaev magnets, including α-RuCl3, Na2IrO3 and β-Li2IrO3, as well as the kagome magnetic metals CrRhAs and CrNiAs. An in depth analysis of the structure and electrical transport behaviour of Na2IrO3 reveals structural domain walls with different degrees of Na deficiency resulting in metallic resistivity down to 2K for a sample with a Na/Ir ratio of 1.1, indicating a local tuning across the metal-to-insulator transition. For α-RuCl3, thermal annealing leads to the formation of RuO2, the influence of which on the low temperature heat capacity as well as magnetic susceptibility and electrical resistivity is described here. FIB microsectioning is utilized for thinning a β-Li2IrO3 single crystal down to ∼1µm for future experiments looking into the dynamics of the systems magnetic and structural ordering parameters, such as dissipative pump-probe spectroscopy. The first successful growth of needle shaped CrRhAs single crystals allows for characterization measurements revealing the material to behave like a typical metal and antiferromagnet. CrNiAs crystals can be grown by the same method used for CrRhAs. Electrical transport, magnetoresistance, Hall effect and magnetic susceptibility are measured and the influence of chemical substitution on TC is investigated. Overall, this thesis shows several possibilities for the application of FIB microstructuring from contacting for electrical transport measurements of micrometre structures to large scale thinning for measurements requiring thin samples of materials which cannot be grown as high quality thin films revealing new information on previously studied honeycomb Kitaev magnets and kagome magnetic metals.…