Experiemental studies of 1D quantum magnets with competing interactions

具有竞争相互作用的一维量子反铁磁材料有望具有新的磁性。本文对金刚石链、三链和锯齿链模型化合物进行了研究。金刚石链状模型化合物Cu_3（A）_2（OH）_2（H_2 O）_4的磁化曲线显示出与1/3磁平台有关的异常。我们研究了三链模型的实际化合物鹿角石和菱镁石。铁角闪石的磁相图非常复杂，而铁角闪石没有长程磁序。虽然这两种化合物的晶体结构相似，但它们的磁性却有很大的不同。结果表明，三重链模型的基态可能会发生量子相变的磁相互作用之间的变化比例。NaCr_2O_4是一种锯齿状链状氧化物，具有庞磁阻效应。从自旋阻挫效应的角度讨论了CMR效应的机理。

One dimensional quantum antiferromagets with competing interactions are expected to have novel magnetic properties. In this study, the diamond chain, triple-chain and zigzag chain model compounds were investigated. The magnetization curve of Cu3(A)2(OH)2(H2O)4, a diamond chain model compound, showed an anomaly related to the 1/3 magnetic plateau. We studied antlerite and szenicsite, actual compound for the triple-chain model. The magnetic phase diagram of antlerite is very complicated, while szenicsite has no long range magnetic order . Although crystal structures of both compounds are similar, their magnetic properties are quite different each other. It is suggested that a quantum phase transition could occur in the ground state of the triple-chain model as varying ratios among magnetic interactions. NaCr2O4, a zigzag chain oxide, was found to have the colossal magnetic resistance (CMR) effect. The mechanism of the CMR effect was discussed in terms of the spin frustration effect.