Bandyopadhyay Abhisek, Das Debu, Chakraborty A, Bhowal S, Kumar Vinod, Stenning G B G, Ritter C, Adroja D T, Moretti Sala M, Efimenko A, Meneghini C, Bert F, Biswas P K, Dasgupta I, Saha Dasgupta T, Mahajan A V, Ray Sugata
ISIS Neutron and Muon Source, STFC, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, United Kingdom.
School of Materials Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700 032, India.
J Phys Condens Matter. 2024 Jul 25;36(42). doi: 10.1088/1361-648X/ad63eb.
Spin-orbit coupling offers a large variety of novel and extraordinary magnetic and electronic properties in otherwise 'ordinary pool' of heavy ion oxides. Here we present a detailed study on an apparently isolated hexagonal 2spin-chainiridate SrLiIrOwith geometric frustration. Our structural studies reveal Li-Ir chemical order with desired stoichiometry in this compound, while x-ray absorption together with x-ray photoemission spectroscopic characterizations establish pure 5+ valence of Ir. We have established a magnetic ground state with finite Irmagnetic moments in this compound, contrary to the anticipated nonmagneticJeff= 0 state, through combined dc susceptibility,7Li nuclear magnetic resonance (NMR), muon spin relaxation (SR) andelectronic structure studies. These investigations together with ac magnetic susceptibility and specific heat measurements reveal that despite having noticeable antiferromagnetic correlation among the Irlocal moments, this system does not magnetically order down to at least 0.05 K, possibly due to geometrical exchange frustration, arising from the comparable nearest- and next-nearest-neighbor interchain Ir-O-O-Ir superexchange interaction strengths with opposite signs. However, the zero-fieldSR analysis shows emergence of a considerable proportion of spin-freezing on top of a spin-fluctuating dynamic magnetic background down to the lowest measured temperature of 1.7 K, possibly due to some inhomogeneity and/or the much stronger intra-column Ir-Ir magnetic exchange interaction strength relative to the inter-column Ir-Ir ones. The linear temperature dependence of the magnetic specific heat (Cm) in both zero and applied magnetic fields, plus the power-law behavior of the NMR spin-lattice relaxation rate suggest a gapless spinon density of states in this charge gapped disordered magnetic ground state of SrLiIrO.
自旋轨道耦合在其他方面均为“普通”的重离子氧化物中展现出了各种各样新颖且非凡的磁学和电学性质。在此，我们对一种看似孤立的具有几何阻挫的六角形双自旋链铱酸盐SrLiIrO进行了详细研究。我们的结构研究揭示了该化合物中具有所需化学计量比的Li-Ir化学有序性，而X射线吸收以及X射线光电子能谱表征确定了Ir的纯5 +价态。通过结合直流磁化率、7Li核磁共振（NMR）、μ子自旋弛豫（SR）和电子结构研究，我们在该化合物中确定了具有有限Ir磁矩的磁性基态，这与预期的非磁性Jeff = 0态相反。这些研究连同交流磁化率和比热测量结果表明，尽管Ir局域磁矩之间存在明显的反铁磁相关性，但由于最近邻和次近邻链间Ir-O-O-Ir超交换相互作用强度相当且符号相反导致的几何交换阻挫，该系统在至少低至0.05 K时仍未发生磁有序。然而，零场SR分析表明，在低至1.7 K的最低测量温度下，在自旋波动的动态磁性背景之上出现了相当比例的自旋冻结，这可能是由于一些不均匀性和/或相对于柱间Ir-Ir磁交换相互作用强度而言，柱内Ir-Ir磁交换相互作用强度要强得多。零场和外加磁场下磁比热（Cm）的线性温度依赖性，加上NMR自旋晶格弛豫率的幂律行为，表明在SrLiIrO这种电荷带隙无序磁性基态中存在无隙自旋子态密度。
