Development of Genuine-Organic Ferromagnets with High Transition Temperature

高压实验是研究各种物质物理性质的基本机制的最有效的方法之一，通过高压实验可以改变或控制物质的电子态和作为压力连续函数的波函数的重叠。我们得到了以下有趣的结果。1.压力下有机弱铁磁体的磁有序化温度与倾斜磁矩的关系.磁相互作用控制TEMPO体系自由基化合物在压力升高下的下降-上升-下降-上升转变温度的机理.压力对真正有机铁磁体的影响：我们测量了典型的有机磁体N ′-二氧-1，3，5，7-四甲基-2，6-二氮杂金刚烷的磁化率和热容，发现居里温度在7 kbar以下有负压效应（Tc = 1.10 K），其磁行为与真正的有机铁磁体原型β相NPNN（Tc = 0.61 K）非常相似。这种化合物在压力下的物理特性有望在应用于后一系统的框架中得到理解。真正有机自旋-Peels体系p-CyDOV的稀释效应：利用Mukai等研究的（p-CyDOV）_<1-x>（p-CyDTV）_x体系，通过热容的测量，我们找到了在低于0.3K的低温下自旋Peel和Neel相共存的浓度范围。这是继CuGeO_3等无机化合物中杂质对自旋Peiels跃迁的影响之后，首次对真正的有机化合物进行的研究。

The high pressure experiment is one of the most effective way to research the fundamental mechanism of physical properties of various materials, by which we can change or control their electronic states and the overlapping of wave functions as a continuous function of pressure. We have got the following results of interest.1. Relation between the enhanced magnetic ordering temperature and the canted magnetic moment in the genuine organic weak-ferromagnets under pressure.2. Mechanism of the magnetic interactions which control the down-up-down-up transition temperature of the TEMPO-system radical compound in the increasing pressures.3. Pressure effects on genuine organic ferromagnets: We have measured the magnetic susceptibility and heat capacity of the typical organic magnet NN'-dioxy-l,3,5,7-tetramethyl-2,6-diazaadamantane Tc = 1.48 K and found the negative pressure effect of the Curie temperature up to 7 kbar(Tc = 1.10 K), whose magnetic behavior quite resembles that of the prototype genuine organic ferromagnet, β-phase NPNN (Tc = 0.61K). The physics of this compound under pressures is expected to be understood in the frame work applied to the latter system.4. Dilution effect of the genuine organic spin-Peiels system p-CyDOV: With the system (p -CYDOV)_<1-x>(p -CyDTV)_x studied by Prof. Mukai et al., we have found the concentration range where the spin-Peiels and the Neel phase coexist at low temperatures below 0.3K by the measurements of heat capacity. Following the impurity effect on the spin Peiels transition for the inorganic compounds, such as CuGeO_3, the present result is the first study with a genuine organic compound.