Study on Mechanism of Interaction in Organic Radical Ferromagnets

有机自由基铁磁体相互作用机理研究

基本信息

批准号：
07454085
负责人：
TAKEDA Kazuyoshi
金额：
$ 4.86万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

The main results of the present research are summarized in two ways ; pressure effects on intermolecular interactions in genuine organic magnetic crystals and cooperative phenomena in many-body quantum Heisenberg spins in low-dimensional systems. We found that the Curie temperature of the first reported organic ferromagnet p-NPNN (para-nitrophenyl nitronyl nitroxide) decreases with hydrostatic pressures by the simultaneous measurements of magnetic susceptibility and heat capacity. The reduction amounts as much as 45% under 7kbar. Recent our experiments in the higher pressures up to 10kbar, however, have revealed the transition temperature turns to increase as the pressure induced enhancement of the Neel temperature of organic antiferromagnets.These results are relevant to competition between the kinetic and the potential exchange interactions via various molecular orbitals under the pressure.The reduction of the lattice dimensionality under pressure is also found to be reflected on the … More change of the magnetic heat capacity of this compound.Quantitative check of quantum statistics in low-dimensional systems is exanined using various crystalline derivatives of verdazyl radical. We measured field and temperature dependence of p-CDTV (3-(4-chlorophenyl-1,5-dimethyl-6-thioxoverdazyl) and got an excellent agreement with the theoretical results for the free energy for one-dimensional quantum ferromagnet, as well as the critical indices of heat capacity and magnetic susceptibility at the limit of zero degree. The staggered susceptibility, which is a fictitious but intrinsic quantity for antiferromagnets, is estimated in a two-demensional quantum Heisen berg Heisenberg antiferromagnet of TOV (1,3,5-triphenyl-6-oxoverdazyl), by making use of the canted weak ferromagnets in this system. The latticedimensional crossover from two to three in antiferromagnetic susceptibility measurements has been revealed. The scaling relation between the staggered susceptibility and the spin correlation length in two-dimensional antiferro-magnet is compared with the present result to make clear the crossover effect feature detected here. Less

目前研究的主要结果概括为两个方面：压力对真正有机磁性晶体中分子间相互作用的影响和低维系统中多体量子海森堡自旋的协同现象。通过同时测量磁化率和热容量，铁磁体 p-NPNN（对硝基苯基硝基硝基氮氧化物）随着静水压力的增加而减少，在这种情况下减少量高达 45%。然而，最近我们在高达 10kbar 的高压下进行的实验表明，随着压力引起有机反铁磁体尼尔温度的升高，转变温度会增加。这些结果与动力学和潜在交换相互作用之间的竞争有关。通过压力下的各种分子轨道。还发现压力下晶格维数的降低反映在该化合物磁热容的变化上。低维系统中量子统计的定量检查我们使用 verdazyl 自由基的各种结晶衍生物进行了检查，测量了 p-CDTV（3-（4-氯苯基-1,5-二甲基-6-thioxoverdazyl））的场和温度依赖性，并与游离的理论结果非常一致。一维量子铁磁体的能量，以及零度极限下的热容量和磁化率的临界指数，这是一个虚构的。但反铁磁体的内在量，通过利用该系统中倾斜的弱铁磁体的晶格维度交叉，在 TOV（1,3,5-三苯基-6-氧代二氮基）的二维量子海森堡反铁磁体中进行估计。已经揭示了反铁磁磁化率测量中的两到三个交错磁化率和自旋相关性之间的比例关系。将二维反铁磁体中的长度与当前结果进行比较，以明确此处检测到的交叉效应特征。