Magnetic-field-induced crossover from the inverse Faraday effect to the optical orientation in EuTe

Abstract

A time-resolved optical pump-probe technique has been applied for studying the ultrafast dynamics in the magnetic semiconductor EuTe near the absorption band gap. We show that application of external magnetic field up to 6 T results in crossover from the inverse Faraday effect taking place on the femtosecond time scale to the optical orientation phenomenon with an evolution in the picosecond time domain. We propose a model which includes both these processes possessing different spectral and temporal properties. The circularly polarized optical pumping induces the optical electronic transition 4f 7 5d 0 → 4f 6 5d 1 forming the absorption band gap in EuTe. The observed crossover is related to a strong magnetic-field shift of the band gap in EuTe at low temperatures. It was found that manipulation of spin states on intrinsic defect levels takes place on a time scale of 19 ps in the applied magnetic field of 6 T.

Femtosecond optical orientation triggering magnetization precession in epitaxial EuO films

“…We note that a sharp peak at zero delay time can be a consequence of the IFE and understood in terms of the third-order optical nonlinearity χ (3) ( ω ; ω , −ω , ω ) when pump and probe beams overlap. 42…”

“…We note that a sharp peak at zero delay time can be a consequence of the IFE and understood in terms of the third-order optical nonlinearity χ (3) (ω; ω, −ω, ω) when pump and probe beams overlap. 42 Fig. 3a and b show the magnetization dynamics for EuO and Eu(Gd)O at different temperatures.…”

Efficient spin excitation via ultrafast damping-like torques in antiferromagnets

“…4 c reveals a difference between the measured and modelled value of the initial phase ϕ 0 . This indicates secondary, non-damping-based excitation mechanisms, such as an optical spin transfer torque 35 , 36 or optical orientation 37 , which could become relevant because of the smallness of α in YMnO 3 as compared to HoMnO 3 . These mechanisms, which are based on absorption rather than spin damping, involve an angular momentum transfer from the circularly polarised pump pulse to the material.…”

Ultrafast Optical Control of Magnetic Interactions in Carrier-Density-Controlled Ferromagnetic Semiconductors

“…Previous experiments on undoped EuO showed that the static conductivity was increased by the irradiation of continuous laser beam [34] and the dynamic enhancement of magnetization by ultrashort laser pulses was possible as demonstrated by means of time-resolved Faraday rotation [35]. In addition, it has been reported that the spin orientation can be controlled by circularly polarized optical pulses via the inverse Faraday effect in EuO [36] and EuTe [37], and the ultrafast dynamics and modulation of the exchange interaction can be accessed using an all-optical technique in EuTe [38]. In this study, ultrafast spin dynamics after the photoexcitation were investigated in carrier-density-controlled ferromagnetic semiconductor Eu 1−x Gd x O films by using a pump-probe nonlinear magneto-optical spectroscopy [39][40][41][42] (Figure 4a), as described below.…”