PDMATHAAB-四-PDMATHAAC-（二甲氨基）-乙烯-C $_{60}$中C $_{60}$分子轨道驱动的反铁磁有序
Antiferromagnetic order driven by the molecular orbital order of C$_{60}$ in $α'$--tetra--$kis$--(dimethylamino)--ethylene--C$_{60}$
摘要：
我们用电子自旋共振（ESR）和磁矩测量研究了富勒烯基磁体$α'$ --相四- $kis$-（二甲氨基）-乙烯-C $_{60}$（$α'$-TDAE-C $_{60}$）的基态。低于T $_N=7$ K时，沿$a$ -轴观察到非顺磁场依赖的共振，其激发带隙为1.7 GHz.随着温度的降低，其强度的强烈增强与单重态的激发不一致，单重态的激发已被提出用于$α'$ -相基态。低于T $_N$，非二次场依赖性的磁转矩信号也观察到相反的二次场依赖性的顺磁相。低于T $_N$的角度相关的转矩信号指示体磁化的各向异性的存在。从这两个实验中，我们提出了一个反铁磁基态驱动的合作取向有序的C $_{60}$的$α'$-TDAE-C $_{60}$。
英文摘要：
We have studied the ground state of a fullerene--based magnet, the $α'$--phase tetra--$kis$--(dimethylamino)--ethylene--C$_{60}$ ($α'$--TDAE--C$_{60}$), by electron spin resonance (ESR) and magnetic torque measurements. Below T$_N=7$ K, non--paramagnetic field dependent resonances with a finite excitation gap (1.7 GHz) are observed along the $a$--axis. Strong enhancement in their intensity as temperature is decreased is inconsistent with excitation from a singlet state, which had been proposed for the $α'$--phase ground state. Below T$_N$, non--quadratic field dependence of magnetic torque signal is also observed in contrast to quadratic field dependence in the paramagnetic phase. The angle--dependent torque signals below T$_N$ indicate the existence of an anisotropy of the bulk magnetization. From both experiments, we propose an antiferromagnetic ground state driven by the cooperative orientational ordering of C$_{60}$ in the $α'$--TDAE--C$_{60}$.
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