Ding Fei, Yang Chuanlu, Gong Xiangnan, Zheng Hui, Zhou Xiaoyu, Li Lingli, Zhang Lichun, Wang Dehua, Pan Bingying
School of Physics and Optoelectronic Engineering, Ludong University Yantai Shandong 264025 China
Analytical and Testing Center, Chongqing University Chongqing 401331 China.
RSC Adv. 2021 Jun 25;11(37):22565-22570. doi: 10.1039/d1ra02318g.
We report the crystal structure and properties of the one-dimensional = 1/2 antiferromagnet Cu(2,6-dimethylpyrazine)Br with strong intra-chain exchange. At room temperature, its linear spin chains are formed by Cu ions the non-bonding Br⋯Br contacts. Interestingly, a phase transition from to 21/ structure occurs at ≈ 248 K below which the [CuBr] spin chains become non-linear and the magnetic susceptibility abruptly increases, reflecting the weakening of antiferromagnetic exchange strength. This result evidences the Goodenough-Kanamori rules which claim that a linear super-exchange pathway produces stronger antiferromagnetic coupling. From magnetic susceptibility measurements we find the average intra-chain exchange strength is / ≈ -88.18 K in the low temperature phase. Both magnetic and specific measurements show the absence of magnetic ordering down to 2 K, implying the excellent magnetic one-dimensionality of Cu(2,6-dimethylpyrazine)Br. We also performed ultra-violet (UV) absorption and photoluminescence measurements which give a semiconducting band gap ≈ 2.79 eV which is consistent with theoretical calculations.
我们报道了具有强链内交换作用的一维自旋为1/2的反铁磁体Cu(2,6 - 二甲基吡嗪)Br的晶体结构和性质。在室温下，其线性自旋链由铜离子通过非键合的Br⋯Br接触形成。有趣的是，在约248 K时发生从 到21/结构的相变，在此温度以下，[CuBr]自旋链变为非线性，并且磁化率突然增加，这反映了反铁磁交换强度的减弱。这一结果证明了古迪纳夫 - 金森规则，即线性超交换路径会产生更强的反铁磁耦合。通过磁化率测量，我们发现在低温相中平均链内交换强度为/≈ - 88.18 K。磁性测量和比热测量均表明直至2 K都不存在磁有序，这意味着Cu(2,6 - 二甲基吡嗪)Br具有优异的磁一维性。我们还进行了紫外（UV）吸收和光致发光测量，得到的半导体带隙≈2.79 eV，这与理论计算结果一致。
