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arXiv · 2607.29676

Magnetic properties of a quasi-two-dimensional spin-1/2 antiferromagnet Y2CuGe4O12

J. Khatua·Changhyun Koo·Suyoung Kim·Eundeok Mun·Yugo Oshima·V. K. Sahu·Heung-Sik Kim·B. Koteswararao·Kwang-Yong Choi·P. Khuntia
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Abstract

Competing magnetic interactions and frustration-induced quantum fluctuations in spatially anisotropic low-dimensional magnets often give rise to exotic magnetic phenomena, including field-induced phases. Here, we present crystal structure, magnetic susceptibility, specific heat, and electron spin resonance (ESR) measurements on polycrystalline Y$2$CuGe$4$O${12}$, supported by density functional theory (DFT) calculations. In this compound, the Cu$^{2+}$ ions form a distorted triangular lattice with competing intraplanar ferromagnetic ($J_1 \approx 0.138$ K and $J_2 \approx 0.01$ K) and antiferromagnetic ($J_3 \approx -3.22$ K) exchange interactions, together with a weaker interplanar antiferromagnetic coupling ($J_4 \approx -1.56$ K). These interactions account for the small Curie--Weiss temperature, $\theta{\rm CW}=-1.8$ K. Despite the dominant antiferromagnetic interactions, no signature of long-range magnetic ordering is observed down to 0.4 K. Instead, broad maxima in both the magnetic susceptibility and magnetic specific heat reveal the development of short-range spin correlations, further supported by the critical ESR linewidth broadening characteristic of low-dimensional frustrated magnets. Application of an external magnetic field progressively suppresses the broad maximum in the magnetic specific heat, reflecting competition between the Zeeman and exchange energy scales, and drives the system into a field-polarized state above the saturation field, $\mu_0H_{\rm s}=2.6$ T. In this regime, the magnetic specific heat exhibits an exponential temperature dependence, consistent with gapped magnon excitations. These results establish Y$_2$CuGe$4$O${12}$ as a rare distorted triangular-lattice magnet in which further-neighbor exchange interactions dominate the magnetic behavior, providing a promising platform for exploring frustration-driven quantum phenomena.

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J. Khatua, Changhyun Koo, Suyoung Kim, Eundeok Mun, Yugo Oshima, V. K. Sahu, Heung-Sik Kim, B. Koteswararao, Kwang-Yong Choi, P. Khuntia. 2026-07-31. Magnetic properties of a quasi-two-dimensional spin-1/2 antiferromagnet Y2CuGe4O12. https://arxiv.org/abs/2607.29676

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