182
7 Opto-spintronics
external magnetic field. The main reasoning force behind this all-optical switching
is ultrafast heating of the electronic system. There are two distinct spin sub-lattices
in GdFeCo. They are aligned antiparallel to each other and bear uncompensated
magnetic moments. Switching of spin takes place in different steps.
First step: With the laser excitation, the magnetic sublattices of the Gd and the FeCo
undergo demagnetization at different rates.
Second step: The exchange of angular momentum takes place between sublattices
that induce a transient ferromagnetic alignment of the two sublattices by flipping the
FeCo spins.
Third step: The antiparallel exchange interaction with the FeCo sublattice causes to
flip Gd sublattice. Hence, spin reversal is completed.
7.11 Conclusion
Opto-spintronics, in which the electronic spin polarization is controlled by light, is
an emerging and fascinating branch of spintronics. Furthermore, optical approach
enables us to manipulate the spin with or without magnetic materials. Development and optimization of future high-speed information storage devices need ultrafast controlling of magnetic order. In spite of the extensive research in last few
decades, there are growing interests in exploring and understanding of femtosecond
laser-assisted spin dynamics. A wide range of materials starting from ferromagnetic metals, semiconductors and clusters to antiferromagnetic dielectrics responds
to light-induced ultrafast demagnetization. In this chapter, we have briefly discussed
the challenges to be overcome along with energy-efficient existing and novel
methods. We also mentioned the effects of optical laser pulse on a magnetic system.
Spin–photon interaction, Faraday effect and inverse Faraday effect have also been
discussed. Different methods for the detection of the changes in the magnetization
in a medium have been investigated. The processes that lead to an optical laserinduced demagnetization have been explained. Laser-induced demagnetization of
GaMnAs, ferromagnetic semiconductor, has been talked about. Special emphasis
has been given on ultrafast optical controlling of magnetic states of antiferromagnet,
i.e., antiferromagnetic opto-spintronics. The outline of different types of all-optical
spintronic switching is also given in this chapter. To stimulate continued advancement of the field, more suitable and functional materials should be investigated
along with novel methods that are efficient in energy and operation. Technologies
associated with computing, communication and control may potentially be revolutionized by the extension of the present state of optical control and modification of
magnetic order toward smaller nanoscale dimensions. Rapid developments in integration of spintronics, nano-photonics and plasmonics bring such possibilities in
7 Opto-spintronics
external magnetic field. The main reasoning force behind this all-optical switching
is ultrafast heating of the electronic system. There are two distinct spin sub-lattices
in GdFeCo. They are aligned antiparallel to each other and bear uncompensated
magnetic moments. Switching of spin takes place in different steps.
First step: With the laser excitation, the magnetic sublattices of the Gd and the FeCo
undergo demagnetization at different rates.
Second step: The exchange of angular momentum takes place between sublattices
that induce a transient ferromagnetic alignment of the two sublattices by flipping the
FeCo spins.
Third step: The antiparallel exchange interaction with the FeCo sublattice causes to
flip Gd sublattice. Hence, spin reversal is completed.
7.11 Conclusion
Opto-spintronics, in which the electronic spin polarization is controlled by light, is
an emerging and fascinating branch of spintronics. Furthermore, optical approach
enables us to manipulate the spin with or without magnetic materials. Development and optimization of future high-speed information storage devices need ultrafast controlling of magnetic order. In spite of the extensive research in last few
decades, there are growing interests in exploring and understanding of femtosecond
laser-assisted spin dynamics. A wide range of materials starting from ferromagnetic metals, semiconductors and clusters to antiferromagnetic dielectrics responds
to light-induced ultrafast demagnetization. In this chapter, we have briefly discussed
the challenges to be overcome along with energy-efficient existing and novel
methods. We also mentioned the effects of optical laser pulse on a magnetic system.
Spin–photon interaction, Faraday effect and inverse Faraday effect have also been
discussed. Different methods for the detection of the changes in the magnetization
in a medium have been investigated. The processes that lead to an optical laserinduced demagnetization have been explained. Laser-induced demagnetization of
GaMnAs, ferromagnetic semiconductor, has been talked about. Special emphasis
has been given on ultrafast optical controlling of magnetic states of antiferromagnet,
i.e., antiferromagnetic opto-spintronics. The outline of different types of all-optical
spintronic switching is also given in this chapter. To stimulate continued advancement of the field, more suitable and functional materials should be investigated
along with novel methods that are efficient in energy and operation. Technologies
associated with computing, communication and control may potentially be revolutionized by the extension of the present state of optical control and modification of
magnetic order toward smaller nanoscale dimensions. Rapid developments in integration of spintronics, nano-photonics and plasmonics bring such possibilities in