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

实验表明，磁性材料对光照射的磁响应是多种多样的。顺磁配合物经圆偏振光照射后，角动量被转移到自旋体系中，根据自旋轨道耦合的对称性所产生的吸收带在自旋方向上产生不同的极性。此外，对于有机溶液中具有S=5/2光致塞曼相干的Fe（III）自旋体系，在垂直于光束的外磁场中成功检测到自由感应衰减信号。另一方面，无论光偏振如何，在磁场存在下，光引发的塞曼态混合产生绝热自旋取向，并表现出特有的磁场依赖性。在特殊情况下，这种自旋取向的状态混合有助于识别单核配合物和双核配合物。对于磁有序体系，尽管光的磁响应主要是由热注入引起的，但有趣的光触发效应，如快速畴壁振荡和磁化反转，取决于外加磁场、光强和温度。上面提到的各种光响应都是用纳秒级的时间分辨率检测到的。这些反应强烈地表明了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.