Disorder-induced spin-liquid-like behavior in kagome-lattice compounds

Quantum spin liquids (QSLs) are an exotic state of matter that is subject to extensive research. However, the relationship between the ubiquitous disorder and the QSL behaviors is still unclear. Here, by performing comparative experimental studies on two kagomé-lattice QSL candidates, Tm3Sb3Zn2O14 and Tm3Sb3Mg2O14, which are isostructural to each other but with strong and weak structural disorder, respectively, we show unambiguously that the disorder can induce spin-liquid-like features. In particular, both compounds show dominant antiferromagnetic interactions with a Curie-Weiss temperature of -17.4 and -28.7 K for Tm3Sb3Zn2O14 and Tm3Sb3Mg2O14, respectively, but remain disordered down to about 0.05 K. Specific-heat results suggest the presence of gapless magnetic excitations characterized by a residual linear term. Magnetic excitation spectra obtained by inelastic neutron scattering (INS) at low temperatures display broad continua. All these observations are consistent with those of a QSL. However, we find in Tm3Sb3Zn2O14, which has strong disorder resulting from the random mixing of the magnetic Tm3+ and nonmagnetic Zn2+, that the low-energy magnetic excitations observed in the specific-heat and INS measurements are substantially enhanced compared to those of Tm3Sb3Mg2O14, which has much less disorder. We believe that the effective spins of the Tm3+ ions in the Zn2+/Mg2+ sites give rise to the low-energy magnetic excitations, and the amount of the occupancy determines the excitation strength. These results provide direct evidence of the mimicry of a QSL caused by disorder. ©2020 American Physical Society.

Description

The work was supported by the National Natural Science Foundation of China with Grants No. 11822405, No. 12074174, No. 11674157, No. 11674158, No. 11774152, No. 11904170, No. 12004249, and No. 12004251, National Key Projects for Research and Development of China with Grant No. 2016YFA0300401, Natural Science Foundation of Jiangsu Province with Grants No. BK20180006 and No. BK20190436, Shanghai Sailing Program with Grant No. 20YF1430600, Fundamental Research Funds for the Central Universities with Grant No. 020414380117, and the Office of International Cooperation and Exchanges of Nanjing University. H.-F.L. acknowledges financial support from the Science and Technology Development Fund, Macau SAR (Files No. 028/2017/A1 and No. 0051/2019/AFJ). We acknowledge stimulating discussions with Itamar Kimchi. We thank the ACNS at ANSTO for the access of neutron-scattering facilities through Proposals No. 7312 and No. 7314, and the excellent support from Gene Davidson from the Sample Environment Group for setting up the dilution refrigerator on PELICAN.

Keywords

Spin, Liquids, Thulium, Antimony, Zinc, Magnesium, Neutron diffraction, Temperature range, Ions

Citation

Ma, Z., Dong, Z.-Y., Wu, S., Zhu, Y., Bao, S., Cai, Z., Wang, W., Shangguan, Y., Wang, J., Ran, K., Yu, D., Deng, G., Mole, R. A., Li, H.-F., Yu, S.-L., Li, J.-X., & Wen, J. (2020). Disorder-induced spin-liquid-like behavior in kagome-lattice compounds. Physical Review B, 102(22), 224415. doi:10.1103/PhysRevB.102.224415