Static and dynamic properties of the frustrated spin-1/2 depleted-kagome antiferromagnet Cu${}_7$(TeO${}_3$)${}_2$(SO${}_4$)${}_2$(OH)${}_6$

Abstract

The structural and magnetic properties of the two-dimensional spin-$1/2$ depleted-kagome compound Cu${}_7$(TeO${}_3$)${}_2$(SO${}_4$)${}_2$(OH)${}_6$ are investigated using x-ray diffraction, magnetization, heat capacity, and ${}^1$H Nuclear Magnetic Resonance (NMR) measurements. From the analysis of magnetic susceptibility, we found a large Curie-Weiss temperature [${\theta }_{\mathrm{CW}}=-50(2)$ K] and the co-existence of antiferromagnetic and ferromagnetic interactions. The value of ${\theta }_{\mathrm{CW}}$ gives an estimate of the average nearest-neighbour antiferromagnetic interaction of $J/k_{\mathrm{B}}\simeq 66$ K. The NMR relaxation rates ($1/T_1$ and $1/T_2$) exhibit a peak, providing evidence for a magnetic long-range order at $T^{\ast }\simeq 4$ K which appears to be canted antiferromagnetic type. Heat capacity also features a broad maximum at $T^{\ast }$ that moves towards higher temperatures with increasing magnetic field, reflecting defect induced Schottky anomaly. The frustration parameter $f_r=|{\theta }_{\mathrm{CW}}|/T^{\ast }\simeq 12.5$ renders the compound a highly frustrated low-dimensional magnet.

Phys. Rev. B (Accepted), 13 pages, 10 figures, and 67 references