FLEET seminar. Unusual spin dynamics in the low-temperature magnetically ordered state of Ag3LiIr2O6

Prof. Avinash Mahajan, Indian Institute of Technology Bombay

Venue: G29 New Horizons Building, Monash University (20 Research Way, Clayton)

And on Zoom. See registration below. Lunch and networking following the seminar

Recently, there have been contrary claims of Kitaev spin-liquid behaviour and ordered behavior in the honeycomb compound Ag₃LiIr₂O₆ based on various experimental signatures. Our investigations on this system (see Phys. Rev. B 104, 115106 (2021)) reveal a low-temperature ordered state with persistent dynamics down to the lowest temperatures. Magnetic order is confirmed by clear oscillations in the muon spin relaxation (mSR) time spectrum below 9 K till 52 mK.  Coincidentally in ⁷Li nuclear magnetic resonance (NMR), a wipe-out of the NMR signal is observed below about 10 K which again strongly indicates magnetic order in the low temperature regime.  The ⁷Li NMR shift and spin-lattice relaxation rate also show anomalies at around 50 K. They are likely related to the onset of dynamic magnetic correlations, but their origin is not completely clear. Detailed analysis of our mSR data is consistent with a co-existence of incommensurate Neel and striped environments. A significant and undiminished dynamical relaxation rate (~ 5 MHz) as seen in mSR deep into the ordered phase indicates enhanced quantum fluctuations in the ordered state.

Prof Mahajan’s research in the Institute of Technology explores the magnetic properties of various types of low-dimensional quantum magnets. They have worked on various spin-chain and spin-ladder systems. Their current focus is exploring systems with antiferromagnetic interactions and frustrated geometries with the intention is to characterize the pristine materials and dope them to induce a change of the ground state and low-energy excitations.