Open Access

Franziska Grußler

• Quantum spin liquids (QSL) have been a focus point of solid state physics in the last decades. They evade magnetic order down to lowest temperatures, host exotic phenomena like fractionalized excitations and are potentially connected to high-temperature superconductivity. Many types of QSLs have been proposed theoretically, but the search for real-life QSL materials has been unsuccessful so far. The synthesis and investigation of YbMgGaO4 in 2014 gave new momentum to the research of triangular antiferromagnets. It showed QSL like behavior in different measurements but unfortunately is tarnished by disorder in the non-magnetic layer. This disorder has a strong impact on the properties of the material and the initial interpretation of YbMgGaO4 as a QSL had to be abandoned. The focus of this thesis is the synthesis and investigation of the compound family AYbX2 (A=K,Na; X=O,S,Se) closely related to YbMgGaO4. Five members of the AYbX2 compound have been successfully prepared: NaYbO2,Quantum spin liquids (QSL) have been a focus point of solid state physics in the last decades. They evade magnetic order down to lowest temperatures, host exotic phenomena like fractionalized excitations and are potentially connected to high-temperature superconductivity. Many types of QSLs have been proposed theoretically, but the search for real-life QSL materials has been unsuccessful so far. The synthesis and investigation of YbMgGaO4 in 2014 gave new momentum to the research of triangular antiferromagnets. It showed QSL like behavior in different measurements but unfortunately is tarnished by disorder in the non-magnetic layer. This disorder has a strong impact on the properties of the material and the initial interpretation of YbMgGaO4 as a QSL had to be abandoned. The focus of this thesis is the synthesis and investigation of the compound family AYbX2 (A=K,Na; X=O,S,Se) closely related to YbMgGaO4. Five members of the AYbX2 compound have been successfully prepared: NaYbO2, KYbO2, NaYbSe2 KYbS2 and KYbSe2. All compounds where characterized through powder (synchrotron) XRD measurements and their basic properties were investigated via ESR, magnetization, susceptibility and specific heat measurements. No magnetic order is observed down to the lowest available temperature of 0.4 K in zero field for all compounds. Applying a magnetic field induces magnetic order. The field-evolution of the magnetic order is traced by susceptibility and magnetization measurements in applied fields up to 7 T and down to 0.4 K. The obtained results are compared to understand the effect of exchanging the alkaline or chalcogen atom on the magnetic properties of the the AYbX2 compounds. Additionally, the doping series KYb(SxSe(1-x))2 has been synthesized and characterized for the first time in this work. The investigation of the doping series is a promising starting point to understand the role of disorder in the QSL formation.…