Center for Integrated Nanotechnologies, Los Alamos National Laboratory, MS K771, Los Alamos, New Mexico 87545, USA.
Nat Commun. 2014 Dec 23;5:5832. doi: 10.1038/ncomms6832.
A new approach to all-optical detection and control of the coupling between electric and magnetic order on ultrafast timescales is achieved using time-resolved second-harmonic generation (SHG) to study a ferroelectric (FE)/ferromagnet (FM) oxide heterostructure. We use femtosecond optical pulses to modify the spin alignment in a Ba(0.1)Sr(0.9)TiO3 (BSTO)/La(0.7)Ca(0.3)MnO3 (LCMO) heterostructure and selectively probe the ferroelectric response using SHG. In this heterostructure, the pump pulses photoexcite non-equilibrium quasiparticles in LCMO, which rapidly interact with phonons before undergoing spin-lattice relaxation on a timescale of tens of picoseconds. This reduces the spin-spin correlations in LCMO, applying stress on BSTO through magnetostriction. This then modifies the FE polarization through the piezoelectric effect, on a timescale much faster than laser-induced heat diffusion from LCMO to BSTO. We have thus demonstrated an ultrafast indirect magnetoelectric effect in a FE/FM heterostructure mediated through elastic coupling, with a timescale primarily governed by spin-lattice relaxation in the FM layer.
采用时间分辨二次谐波产生（SHG）技术研究铁电（FE）/铁磁（FM）氧化物异质结构，实现了超快时间尺度上对电和磁有序耦合的全光探测和控制的新方法。我们使用飞秒光脉冲来改变 Ba(0.1)Sr(0.9)TiO3 (BSTO)/La(0.7)Ca(0.3)MnO3 (LCMO) 异质结构中的自旋排列，并使用 SHG 选择性地探测铁电响应。在这种异质结构中，泵浦脉冲在 LCMO 中光激发非平衡准粒子，这些准粒子在经历数十皮秒的自旋晶格弛豫之前与声子快速相互作用。这会降低 LCMO 中的自旋关联，通过磁致伸缩对 BSTO 施加应力。这会通过压电效应来改变 FE 极化，其时间尺度比 LCMO 到 BSTO 的激光诱导热扩散快得多。因此，我们在通过弹性耦合介导的 FE/FM 异质结构中证明了超快间接磁电效应，其时间尺度主要由 FM 层中的自旋晶格弛豫决定。
