Low-dimensional magnets may realize a spin disorder ground state due to the strong spin fluctuation. Such unusual magnetic ground states and their quantum critical behaviors have attracted great scientific interest in the fields of materials science and condensed matter physics.
A research team led by Prof. HE Zhangzhen from Fujian Institute of Research on the Structure of Matter (FJIRSM), Chinese Academy of Sciences (CAS), recently found two isostructural compounds BiOCu2(XO3)(SO4)(OH)·H2O (X = Te and Se) with a unique spin lattice, in which the topological structure of magnetic Cu2+ ions shows a new two-dimensional (2D) frustrated motif (named as octa-kagome) between regular kagome and star lattices.
Usually magnetic compounds with a same spin lattice show a similar magnetic behavior. Interestingly and surprisingly, the results combined from magnetic and heat capacity measurements however suggest different magnetic behaviors between the above isostructural compounds, in which Te-analogue has a nonmagnetic spin-gap ground state and Se-analogue possesses an antiferromagnetic ordering at low temperature.
A theoretical simulation was performed by Co-authors Prof. SU Gang From University of Chinese Academy of Sciences, indicating that the nature of different magnetic behaviors is due to the dimerization of Cu2+ ions for Te-analogue, while Se-analogue may break the limiting of such dimerization.
As new type of geometrically frustrated lattice compounds, BiOCu2(XO3)(SO4)(OH)·H2O (X = Te and Se) are quite rare examples of 2D spin systems that can realize such order-disorder quantum phase transition induced by a substitution of nonmagnetic anionic group.
The study entitled “Octa-Kagomé Lattice Compounds Showing Quantum Critical Behaviors: Spin Gap Ground State versus Antiferromagnetic Ordering” has been published in J. Am. Chem. Soc..
Structural evolution of octa-kagome lattice from regular kagome and star lattices, showing different magnetic behaviors between Te- and Se-analogues.(Image by Prof. HE’s group)
Contact:
Prof. HE Zhangzhen
Fujian Institute of Research on the Structure of Matter
Chinese Academy of Sciences
Email: hzz@fjirsm.ac.cn