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Volume 6
Research & Reviews: Journal of Material Sciences
ISSN: 2321-6212
Magnetic Materials 2018
October 22-23, 2018
October 22-23, 2018 | Rome, Italy
3
rd
International Conference on
Magnetism and Magnetic Materials
Photo-induced magneto-optical phenomena in magnetic semiconductors: Europium chalcogenides
Victor Pavlov
Ioffe Institute of Russian Academy of Sciences, Russia
E
uropium chalcogenides EuX (X = O, S, Se, Te) are a compact group of magnetic semiconductors with unique electronic,
magnetic, optical and magneto-optical properties. The physical properties of the europium chalcogenides EuX are determined
by the electronic structure of the Eu
2+
ions, which have strongly localized 4
f
7
electrons with a large spin S = 7/2. A photo-induced
Faraday effect (FE) was studied in the chalcogenides EuTe and EuSe by the optical pump-probe technique using continuous
lasers and a broadband light source. The photo-induced FE was investigated as a function of the intensity of light, magnetic field,
and temperature. Figure 1 shows field dependences of the photo-induced FE in EuTe at various optical pumping intensities. It
has been established that resonant excitation of the 4f
7
5d
0
→ 4f
6
5d
1
optical electric-dipole transition in EuTe produces magnetic
polarons with a quantum efficiency of about 10% and a magnetic moment exceeding 600 μB for EuTe and 6000 μB EuSe at
low temperatures. A quantum mechanical model has been developed for calculating the photoinduced FE associated with the
formation of giant magnetic polarons in EuTe. The developed theory describes well the experimentally observed dependencies.
The optical pump-probe technique with a femtosecond time resolution was used to study ultrafast dynamics in EuTe near
the absorption band gap. A magnetic-field-induced crossover from the inverse FE to the optical orientation was observed. In
conclusion, a number of new photo-induced optical effects in magnetic semiconductors EuX were observed.
Figure 1: (a)
Field dependences of the photo-induced FE in EuTe at various optical pumping intensities. (b) Photo-induced polarons form a paramagnetic ensemble:
in the zero magnetic field each polaron has an arbitrary orientation, the average magnetic moment is zero. (c) Due to the large magnetic moment of the polaron a
small magnetic field is needed to align all polarons at low temperature.
Recent Publications
1. Henriques A B, Naupa A R, Usachev P A, Pavlov V V, Rappl P H O and Abramof E (2017) Photoinduced giant
magnetic polarons in EuTe. Physical Review B 95:045205.
2. Henriques AB, Gratens X, Usachev PA, ChittaVAand SpringholzG (2018) Ultrafast light switching of ferromagnetism
in EuSe. Physical Review Letters 120: 217203.
3. Henriques A B and Usachev P A (2017) Faraday rotation by the undisturbed bulk and by photoinduced giant polarons
in EuTe. Physical Review B 96:195210.
4. Henriques A B, Galgano G D, Rappl P H O and Abramof E (2016) Light-induced polaron magnetization in EuTe at
temperatures reaching 150 K. Physical Review B 93:201201(R).
5. Pavlov V V, Pisarev R V, Nefedov S G, Akimov I A, Yakovlev D R, Bayer M, Henriques A B, Rappl P H O and Abramof
E (2018) Magnetic-field-induced crossover from the inverse Faraday effect to the optical orientation in EuTe. Journal
of Applied Physics 123:193102.
Victor Pavlov, Res. Rev. J Mat. Sci. 2018, Volume 6
DOI: 10.4172/2321-6212-C6-029