Fitzky Gabriel, Nakajima Makoto, Koike Yohei, Leitenstorfer Alfred, Kurihara Takayuki
Department of Physics and Center for Applied Photonics, University of Konstanz, D-78457 Konstanz, Germany.
Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Phys Rev Lett. 2021 Sep 3;127(10):107401. doi: 10.1103/PhysRevLett.127.107401.
We compare the ultrafast dynamics of the spin reorientation transition in the orthoferrite Sm_{0.7}Er_{0.3}FeO_{3} following two different pumping mechanisms. Intense few-cycle pulses in the midinfrared selectively excite either the f-f electronic transition of Sm^{3+} or optical phonons. With phonon pumping, a finite time delay exists for the spin reorientation, reflecting the energy transfer between the lattice and 4f system. In contrast, an instantaneous response is found for resonant f-f excitation. This suggests that 4f electronic pumping can directly alter the magnetic anisotropy due to the modification of 4f-3d exchange at femtosecond timescales, without involving lattice thermalization.
我们比较了正铁氧体Sm₀.₇Er₀.₃FeO₃在两种不同泵浦机制下自旋重取向转变的超快动力学。中红外波段的强少周期脉冲选择性地激发Sm³⁺的f-f电子跃迁或光学声子。在声子泵浦情况下，自旋重取向存在有限的时间延迟，这反映了晶格与4f体系之间的能量转移。相比之下，对于共振f-f激发，发现了瞬时响应。这表明4f电子泵浦可在飞秒时间尺度上通过改变4f-3d交换直接改变磁各向异性，而无需涉及晶格热化。
