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arXiv · 1002.3068

High Field ESR and Magnetization of the Triangular Lattice Antiferromagnet NiGa2S4

Hironori Yamaguchi·Shojiro Kimura·Masayuki Hagiwara·Yusuke Nambu·Satoru Nakatsuji·Yoshiteru Maeno·Akira Matsuo·Koichi Kindo
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Abstract

We report the experimental and the analytical results of electron spin resonance (ESR) and magnetization in high magnetic fields up to about 68 T of the quasi two-dimensional triangular lattice antiferromagnet NiGa$_2$S$_4$. From the temperature evolution of the ESR absorption linewidth, we find a distinct disturbing of the development of the spin correlation by $Z_2$-vortices between 23 K and 8.5 K. Below $T_{\rm{v}}=8.5$ K, spin-wave calculations based on a 57$^{\circ}$ spiral spin order well explains the frequency dependence of the ESR resonance fields and high field magnetization processes for $H$$\parallel$$c$ and $H$$\perp$$c$, although the magnetization for $H$$\perp$$c$ at high fields is different from the calculated one. Furthermore, we explain the field independent specific heat with $T^2$-dependence by the same spin-wave calculation, but the magnitude of the specific heat is much less than the observed one. Accordingly, these results suggest the occurrence of a $Z_2$ vortex-induced topological transition at $T_{\rm{v}}$ and may indicate quantum effects beyond the descriptions based on the above classical spin models.

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Hironori Yamaguchi, Shojiro Kimura, Masayuki Hagiwara, Yusuke Nambu, Satoru Nakatsuji, Yoshiteru Maeno, Akira Matsuo, Koichi Kindo. 2010-02-15. High Field ESR and Magnetization of the Triangular Lattice Antiferromagnet NiGa2S4. https://doi.org/10.1143/jpsj.79.054710

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