High time-resolution measurement of transient magnetism using opto-electric response

从实验上阐明了磁性材料对光照射的磁响应是多种多样的。当材料被圆偏振光照射时，顺磁性复合物的角动量被转移到自旋系统，从而根据自旋轨道耦合对称性导致的吸收带产生不同的自旋取向极性。此外，对于Fe（III）自旋系统在有机溶液中与S=5/2的光诱导塞曼相干被成功地检测到作为一个自由感应衰减信号在外部磁场垂直于光束。另一方面，无论光偏振，在磁场存在下光学引发的塞曼态混合产生绝热自旋取向，并表现出特征的磁场依赖性。在特定情况下，这种由态混合引起的自旋取向有助于单核络合物和双核络合物的鉴别。对于磁有序体系，虽然光辐射下的磁响应主要是热注入引起的，但由于磁场、光强度和温度的不同，磁有序体系也会产生一些有趣的光触发效应，如畴壁的快速振荡和磁化反转等，上述各种光响应都能在纳秒级的时间分辨率下被探测到.这些响应强烈表明进一步提高磁探测时间分辨率的兴趣和重要性。

It is elucidated experimentally that the magnetic response to light irradiation is very diverse in magnetic materials. When the material is irradiated by a circularly polarized light for paramagnetic complexes angular momentum is transferred to the spin system giving rise to different polarities in spin orientation depending on the absorption bands resulting from the symmetry of spin-orbit coupling. Also, for Fe(III) spin system in organic solution with S=5/2 photo-induced Zeeman coherence was successfully detected as a free-induction decay signal in the external magnetic field perpendicular to the light beam. On the other hand regardless of light polarization optically initiated Zeeman state mixing in the presence of magnetic field creates adiabatic spin orientation and exhibits characteristic magnetic-field dependence. For a particular case such a spin orientation by the state mixing can contribute to identification of mono-nuclear complex and di-nuclear complex. For magnetically ordered systems although the magnetic responses to light irradiation are mostly those originating from heat injection, interesting photo-triggered effects such as the fast domain-wall oscillation and magnetization inversion depending on the applied magnetic field, light intensity, and temperature.A variety of photo-responses mentioned above are all detected with the nanosecond time resolution. These responses strongly suggest interest and importance of further improvement of time resolution in magnetic detection.