Sr $_2$ CuWO $_6$是一种双钙钛矿，被认为处于二维和三维磁性之间的边界，具有$S=\frac{1}{2}$ Cu $^{2+}$离子的方形晶格。我们已经使用非弹性中子散射研究系统的自旋波激发，找出它们如何演变为温度的函数，以及获得有关磁交换相互作用的信息。我们在$6$ ~K处观察到了定义良好的色散自旋波模，它在磁有序温度$T_N=24$ ~K以上部分存活。线性自旋波理论被用来确定交换相互作用揭示他们是高度二维的性质。密度泛函理论计算支持这一实验结果，这是在对比以前的\emph{ab-initio}研究的磁相互作用。我们的分析证实，不是最近的邻居，但下一个最近的邻居在四重$ab$平面的相互作用是最强的。低入射能量的测量揭示了$0.6(1)$ ~meV间隙低于$T_N$，这表明存在一个非常弱的单离子各向异性项的形式，沿$\hat{\mathbf{a}}$的易轴的开放。
英文摘要：
Sr$_2$CuWO$_6$ is a double perovskite proposed to be at the border between two and three dimensional magnetism, with a square lattice of $S=\frac{1}{2}$ Cu$^{2+}$ ions. We have used inelastic neutron scattering to investigate the spin wave excitations of the system, to find out how they evolve as a function of temperature, as well as to obtain information about the magnetic exchange interactions. We observed well defined dispersive spin wave modes at $6$~K, which partially survive above the magnetic ordering temperature, $T_N=24$~K. Linear spin wave theory is used to determine the exchange interactions revealing them to be highly two-dimensional in nature. Density functional theory calculations are presented supporting this experimental finding, which is in contrast to a previous \emph{ab-initio} study of the magnetic interactions. Our analysis confirms that not the nearest neighbour, but the next nearest neighbour interactions in the tetragonal $ab$ plane are the strongest. Low incident energy measurements reveal the opening of a $0.6(1)$~meV gap below $T_N$, which suggests the presence of a very weak single ion anisotropy term in the form of an easy axis along $\hat{\mathbf{a}}$.
Quasi two dimensional magnetic structure of the triclinic double perovskite Ca$_2$CuWO$_6$
University College London（伦敦大学学院）；Durham University（杜伦大学）；STFC Rutherford Appleton Laboratory（STFC卢瑟福阿普尔顿实验室）；National Institute for Materials Science (NIMS)（国立材料研究所）；Hokkaido University（北海道大学）
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