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P. Khuntia1, S. Manni2, P. Gegenwart2 and M. Baenitz1
1 Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany 2 I. Physikalisches Institut, Georg-August-Universität Göttingen, D-37077, Göttingen, Germany Strongly correlated electron systems have provided a plethora of exotic phenomena stemming from competing interactions driven by charge, spin and orbital degrees of freedom in their collective ground states [1-3]. Recently, 5d iridates especially the honeycomb lattice systems Na2IrO3 and Li2IrO3 earned great attention because they display exciting magnetic properties which are driven by strong spin orbit coupling (SOC). Even in the structural homologue Li2RhO3, 4d magnetism associated with strong SOC could be observed [4-8]. Solid state NMR is a very useful tool to study the static and dynamic magnetism on a microscopic level and 7Li with a near to 100 % natural abundance and a nuclear spin of I=3/2 is a very novel probe. So far there are no systematic NMR investigations on new SOC dominated d-electron systems. We report a comprehensive temperature and field dependent 7Li (I=3/2) NMR study on Li2IrO3, Li2RhO3 and on the non-magnetic reference compound Li2SnO3. In addition, magnetization and specific heat investigations are conducted. The 7Li-NMR spectra, spin lattice relaxation rate (SLR), magnetization and specific heat reveal that Li2IrO3 is magnetically ordered at TN ~ 15K. Whereas, the 7Li-NMR shift and the line width are showing only weak effects of the 5d-magnetism, the spin lattice relaxation rate shows a clear peak around the ordering temperature. Above the ordering temperature, the shift and line width of Li2IrO3 are reminiscent to the behavior found in 23Na (I=3/2) NMR in Na4Ir3O8. In contrast to that, in Li2RhO3, the 7Li NMR line width has a much stronger temperature and field dependence. The 7Li NMR line width shows a kink around 8 K indicative of glassy behavior while the SLR display a maximum at some what higher temperature, which suggest the onset of spin freezing at about 10 K. References: 1. L. Balents, Nature 464, 199 (2010). 2. P. Gegewart et al., , Nature Physics 4, 186 (2008). 3. S. Sachdev, Nature Physics 4, 173 (2008). 4. Y. Singh and P. Gegenwart, Phys. Rev. B 82, 064412 (2010). 5. Y. Singh et al., Phys. Rev. Lett. 108, 127203 (2012). 6. S. K. Choi et al., Phys. Rev. Lett. 108, 127204 (2012). 7. I. I. Mazin et al arXiv: 1304.2258v1. 8. Y. Lou et al arXiv: 1303.4675v1. |
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