Electron spin resonance spectroscopy on complex iridium oxides

• Applicant: Dr. Vladislav Kataev
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2014 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 260000137

We propose to apply high-frequency high-magnetic field electron spin resonance spectroscopy (HF-ESR) for a systematic study of static and dynamic magnetic properties of complex iridium oxides which have recently emerged as a novel kind of quantum magnets called spin orbital Mott insulators. This class of materials attracts currently very strong attention in the condensed matter physics community worldwide. New quantum magnetic phenomena are expected to occur in the 5d iridates due to a strongly enhanced spin-orbit coupling (SOC) as compared to the 3d cuprates and manganites where the SOC is small and plays only a minor role. The SOC driven entanglement of the spin and orbital momenta is predicted to yield in the iridates new exotic magnetic interactions and ground states, ranging from the antiferromagnetic (AFM) Néel order, to stripy and zigzag AFM spin structures and to a spin liquid state. Since ESR spectroscopy is very sensitive to the SOC related magnetic anisotropies which inter in directly measurable quantities, such as the g-factor tensors and energy gaps for the ESR excitations, this method emerges as an instructive tool to investigate magnetic phases in iridium oxides. We will use the advantages of the HF-ESR instrumentation at the IFW Dresden which enables a high sensitive detection of ESR signals in a very broad frequency range from 0.01 to 1 THz, in fields up to 16 T and at temperatures down to 300 mK. Systematic studies of frequency, magnetic field and orientation dependences of the ESR modes in the poly- and single crystalline samples of iridium oxides with different crystallographic structures and different topologies of the networks of Ir effective spins will allow an accurate determination of the magnetic anisotropies, the spin structures in the ground state and parameters of the low energy spin dynamics. The obtained information should enable to classify the studied materials with respect to the theoretically proposed magnetic phases and should help to verify theoretical models of spin orbital Mott insulators.

• DFG Programme: Research Grants