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arXiv · 2501.05754

Magnetism based on nitrate-nitrate interactions: The cases of LiNO$_3$, K$_{0.5}$Rb$_{0.5}$NO$_3$, Ca(NO$_3$)$_2$ and C(NH$_2$)$_3$NO$_3$

Na Du·Xintian Wang·Ruo Tong Wang·Enting Xu·Yu Ying Zhu·Yan Zhao·Peng Ren·Fei Yen
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Abstract

Long-range magnetic ordering of the orbital motion of oxygen atoms within NO$_3$$^-$ cations is identified from experimental measurements of the magnetic susceptibility $χ$($T$) in LiNO$_3$, Ca(NO$_3$)$_2$, K$_{0.5}$Rb$_{0.5}$NO$_3$ and C(NH$_2$)$_3$NO$_3$ at their respective order-disorder, solid-solid phase transitions $T$$_N$. The observed sharp changes in $χ$($T$) and accompanying hysteretic behavior indicate the phase transitions to be first order. A model employing the law of conservation of angular momentum is used to explain why the librations between neighboring NO$_3$$^-$ become geared below $T$$_N$. Since the periodic motions involve concerted motion of net charges, the associated magnetic moments of the NO$_3$$^-$ ions indirectly establish an antiferromagnetic structure below $T$$_N$. Our findings identify a previously unidentified type of molecular interaction which may be exploited to further increase the enthalpy of the widely-popular hydrated salts employed as energy storage devices.

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Na Du, Xintian Wang, Ruo Tong Wang, Enting Xu, Yu Ying Zhu, Yan Zhao, Peng Ren, Fei Yen. 2025-01-10. Magnetism based on nitrate-nitrate interactions: The cases of LiNO$_3$, K$_{0.5}$Rb$_{0.5}$NO$_3$, Ca(NO$_3$)$_2$ and C(NH$_2$)$_3$NO$_3$. https://arxiv.org/abs/2501.05754

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