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Development of molecular conducting magnets oriented to π-d interaction control

面向π-d相互作用控制的分子导电磁体的研制

基本信息

批准号：
14540530
负责人：
MIYAZAKI Akira
金额：
$ 2.11万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2005
项目状态：
已结题

项目摘要

1. The electrical resistivities and magnetoresistances (MR) of a radical ion salt (EDO-TTFBr_2)_2MCl_4 (M=Fe,Ga) are investigated under pressures. The resistivity of the FeCl4 salt shows two anomalies due to the successive transitions of the π-electron layer, and another anomaly coming from the long-range magnetic ordering of the FeCl_4 layer. For the GaCl_4 salt negative MR is observed in the low-field region, suggesting a decrease of the SDW gap by applying the magnetic field. The MR of the FeCl_4 salt shows two abrupt increases, which proves the presence of field-induced successive transitions in the composite π-d spin system. The field dependence of the MR of this salt can be qualitatively explained based on the frustrated magnetic structure of π- and d-electron spins interacting with each other.2. The magnetic properties of weak ferromagnets (BDH-TTP)[M(isoq)_2(NCS)_4] (M = Cr, Fe ; isoq = isoquinoline) is investigated. These salts form two-dimensional magnetic sheets, where ferri … More magnetic chains of donor cation radical and anion are antiferromagnetically connected by S…S contacts. Under ambient pressure, both the Cr and Fe salts undergo a weak ferromagnetic transition at T_N = 7.6 K. The application of pressure elevates the transition temperatures up to 16.6 K and 11.6 K at 9 kbar for M = Cr and Fe, respectively. The pressure dependence of the remanent magnetization indicates that the spin canting angle of the Cr salt is reduced due to the increase of antiferromagnetic interaction by applied pressure, in contrast to the Fe salt where the Fe spins are more canted due to the increase of the Dzyaloshinsky-Moriya interaction. The mean-field analysis reveals that the intermolecular exchange interaction increases as the pressure increases, among which the inter-chain anion-anion interaction has the highest pressure sensitivity. This result is consistent with the temperature dependence of the crystal structure showing the thermal contraction in the distances of inter-chain anion-anion S…S contacts is the most remarkable in intra-chain S…S contacts. Less

1.本文研究了自由基离子盐（EDO-TTFBr_2）_2MCl_4（M=Fe，Ga）在压力下的电阻率和磁电阻。FeCl_4盐的电阻率表现出两种异常，一种是由于π电子层的连续跃迁，另一种是由于FeCl_4层的长程磁有序。对于GaCl_4盐，在低场区观察到负MR，表明施加磁场减小了SDW带隙。FeCl_4盐的磁电阻出现了两次突变，证明了复合π-d自旋体系中存在场致连续跃迁。这种盐的磁电阻随磁场的变化可以用π-和d-电子自旋相互作用的阻挫磁结构来定性解释.研究了弱铁磁体（BDH-TTP）[M（isoq）_2（NCS）_4]（M = Cr，Fe ; isoq =异喹啉）的磁性。这些盐形成二维磁性片，其中铁 ...更多信息施主阳离子自由基和阴离子的磁性链通过S. S接触反铁磁性连接。在常压下，Cr盐和Fe盐在T_N = 7.6K时均发生弱铁磁转变。的压力的应用升高的转变温度高达16.6 K和11.6 K，在9千巴的M = Cr和Fe，分别。的压力依赖性的reversible磁化表明，由于反铁磁相互作用的增加，通过施加压力的Cr盐的自旋倾斜角减小，在Fe盐的Fe自旋更倾斜，由于增加的Dzyaloshinsky-Moriya相互作用。平均场分析表明，分子间交换作用随压力的增加而增强，其中链间阴离子-阴离子交换作用的压力敏感性最高。这一结果是一致的温度依赖性的晶体结构，显示在链间阴离子-阴离子S的距离的热收缩... S接触是最显着的链内S. S接触。少