论文标题
三角形旋转的变形 - $ \ frac {1} {2} $ rattice in Na $ _2 $ srco（po $ _4 $）$ _ 2 $
Deformation of the triangular spin-$\frac{1}{2}$ lattice in Na$_2$SrCo(PO$_4$)$_2$
论文作者
论文摘要
据报道，Na $ _2 $ srco的晶体结构和热力学特性（PO $ _4 $）$ _ 2 $，三角量子量子旋转式候选na $ _2 $ _2 $ baco（po $ _4 $）$ _ 2 $的化学兄弟姐妹。从单晶X射线衍射和高分辨率同步子X射线粉末衍射中，与Trigonal NA $ _2 $ _2 $ _2 $ baco（PO $ _4 $）$ _ 2 $相比，发现该化合物在室温下单斜空间$ p2_1/a $在室温下结晶。在650 K以上，Na $ _2 $ srco的对称性（PO $ _4 $）$ _ 2 $更改为$ C2/m $，而大约1025 k a则观察到进一步的转换对三角形对称性。单斜形的对称性导致COO $ _6 $ contahedra的小变形超过这种结构类型的三角形失真，并导致更强的$ g $ -g $ -tensor arisotropy（$ g _ {$ g _ {\ text {z}}}}}/g _ _ { （$ j _ {\ text {z}}/j _ {\ text {xy}} = 2.1 $）与ba compound（$ g _ {\ text {z}}/g _ {\ text {z} = 1.5 $），而平均耦合强度，$ j _ {\ text {av}}/k _ {\ text {b}} =（2J _ {\ text {xy}}}+j _ {\ j _ {\ j {\ text {z}}}}}}}}}}）不变。 Néel温度从140 MK（BA）升高到600 MK（SR），而无偿的面内力矩为$ 0.066（4）μ_ {\ text {b}}/\ text {b}}/\ text {f.u。} $。我们表明，三角形反铁磁铁的订购温度受到其结构扭曲的可能控制。
Crystal structure and thermodynamic properties of Na$_2$SrCo(PO$_4$)$_2$, the chemical sibling of the triangular quantum spin-liquid candidate Na$_2$BaCo(PO$_4$)$_2$, are reported. From single crystal x-ray diffraction and high-resolution synchrotron x-ray powder diffraction, the compound was found to crystallize in the monoclinic space group $P2_1/a$ at room temperature, in contrast to the trigonal Na$_2$BaCo(PO$_4$)$_2$. Above 650 K, the symmetry of Na$_2$SrCo(PO$_4$)$_2$ changes to $C2/m$, while around 1025 K a further transformation toward trigonal symmetry is observed. The monoclinic symmetry leads to a small deformation of the CoO$_6$ octahedra beyond the trigonal distortion ubiquitous in this structure type, and results in the stronger $g$-tensor anisotropy ($g_{\text{z}}/g_{\text{xy}} = 1.6 $) as well as the increased XXZ anisotropy ($J_{\text{z}}/J_{\text{xy}} = 2.1$) compared to the Ba compound ($g_{\text{z}}/g_{\text{xy}} = 1.1 $, $J_{\text{z}}/J_{\text{xy}} = 1.5$), while the average coupling strength, $J_{\text{av}}/k_{\text{B}}=(2J_{\text{xy}}+J_{\text{z}})/3k_\text{B}\simeq 1.3\,\text{K}$, remains unchanged. The Néel temperature increases from 140 mK (Ba) to 600 mK (Sr), and an uncompensated in-plane moment of $0.066(4)μ_{\text{B}}/\text{f.u.}$ appears. We show that the ordering temperature of a triangular antiferromagnet is capably controlled by its structural distortions.
