Structural and physical properties of high-pressure polymer phase of fullerene ferromagnet

1.富勒烯铁磁体α-TDAE-C_(60)的晶格参数和铁磁性的压力变化我们用金刚石顶压室测量了α-TDAE-C_(60)铁磁性多晶型的晶格参数的压力变化。我们发现，与链间长度相比，沿最近邻C_(60)&gt；的链内长度几乎不依赖于压力。沿b轴(链间方向)的压缩系数估计为db/dp=-0.042Å/kbar。在临界压力Pc=0.6 Gpa以上，X射线照片发生了很大的变化，这应该与一级结构相变到高压聚合物相有关，然而，由于观测反射的限制，我们未能成功地解决Pc以上的结构问题。我们使用了为SQUID磁强计开发的圆柱型高压盒，以澄清体磁是否依赖于压力。饱和磁化强度和居里温度均明显依赖于压强，且随压强的增加而抑制。Pc以上的类居里磁化率表明自旋载流子在聚合物相中的局域化。2.多晶型α‘-TDAE-C；60&gt；60&gt；的反铁磁性相变我们测量了低频电子自旋共振和高灵敏磁矩，以阐明多晶型α’-TDAE-C_&lt；60&gt；的低温磁基态。首次发现α‘相在7K以下发生反铁磁相变。我们的结构研究清楚地表明了两个多态之间的结构差异。因此，对α‘相的磁性测量表明，磁性与低温结构之间存在明显的相关性。富勒烯基磁体的磁性强烈地依赖于C&lt；60和Gt；之间的分子间接触以及C&lt；60和Gt；的轨道自由度。

1.Pressure variation of lattice parameters and ferromagnetism in the fullerene ferromagnet α-TDAE-C_<60>We have measured a pressure variation of lattice parameters in the ferromagnetic polymorphs, α-TDAE-C_<60> using the diamond anvil cell (DAC). We have found that the intrachain length along the nearest-neighbor C_<60> hardly depends on the pressure as compared with the lengths between chains. The compressibility along the b-axis (interchain direction) is estimated to be db/dP= - 0.042Å/kbar. Above the critical pressure Pc=0.6GPa, the X-ray photographs have been drastically changed, which should be related to the first-order structural phase transition to the high-pressure polymeric phase, however, we could not succeeded in solving the structure above Pc due to a limit in observed reflections.We have used a cylinder-type high pressure cell, which was developed for the SQUID magnetometer, in order to clarify whether the bulk magnetism depends on the pressure. Both the saturation magnetization and the Curie temperature clearly depend on the pressure and suppressed with increasing the pressure. The Curie-like susceptibility above Pc indicates the localization of spin-carrier in the polymeric phase.2.Antiferromagnetic phase transition in the polymorphic α'-TDAE-C_<60>We have measured the low-frequency electron spin resonance and high-sensitive magnetic torque in order to clarify the low-temperature magnetic ground state of polymorphic α'-TDAE-C_<60>. It is found for the first time that the α'-phase undergoes an antiferromagnetic transition below 7K. Our structural study clearly indicates the structural deference between two polymorphs. Therefore, the magnetic measurements on the α'-phase establishes that the clear correlation between the magnetism and the low-temperature structure. The magnetism of the fullerene-based magnet strongly depends on the intermolecular contact between C_<60> and the degree of freedom of orbitals of C_<60>.