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

TL;DR

This study investigates the ultrafast magnetic and optical dynamics in EuTe, revealing a magnetic-field-driven crossover from the inverse Faraday effect to optical orientation within picoseconds.

Contribution

It introduces a model describing the transition between inverse Faraday effect and optical orientation in EuTe under magnetic fields, highlighting the role of band gap shifts.

Findings

Crossover from inverse Faraday effect to optical orientation observed.

Magnetic field causes a significant shift in EuTe's band gap.

Spin state manipulation occurs within 19 ps at 6 T.

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 $4f^75d^0 \rightarrow 4f^65d^1$ 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.