Ultrafast Control of Magnetic Anisotropy by Resonant Excitation of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mn>4</mml:mn><mml:mi>f</mml:mi></mml:mrow></mml:math> Electrons and Phonons in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>Sm</mml:mi></mml:mrow><mml:mrow><mml:mn>0.7</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi>Er</mml:mi></mml:mrow><mml:mrow><mml:mn>0.3</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi>FeO</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>
Gabriel Fitzky, Makoto Nakajima, Yohei Koike, Alfred Leitenstorfer, Takayuki Kurihara
Abstract
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.