1.3 Research Efforts Put on Spintronics
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manner. In this direction, spin relaxation and transport in both metallic and semiconducting samples are subject of intense research interest, not only for issues related to
fundamental solid-state physics but also for their potential in electronic technology.
Designing and manufacturing of spintronic devices are executed by two different
approaches. The first approach is to achieve improvement in the existing giantmagnetoresistive (GMR)-based technology. In this direction, a very preliminary
attempt is to explore new materials having even larger electron spin polarization.
Another attempt includes improving upon the existing GMR devices in order to
obtain better spin filtering. In GMR-based industry, the already existing operational prototype device is the read head and memory storage cell. This is basically a
GMR sandwich structure, consisting of alternating ferromagnetic and non-magnetic
metallic layers. It is the relative magnetizations alignment in the adjacent ferromagnetic layers that decide the device resistance. For instance, device resistance is
small for parallel alignment of magnetizations, whereas it is large for antiparallel
alignment. Such change in resistance, referred to as magnetoresistance, is utilized to
sense variations in magnetic fields. In recent efforts, magnetic tunnel junction-based
devices have also been involved in GMR technology. In magnetic tunnel junctions,
tunnelling current depends on the orientations of magnetizations of the electrodes.
The second approach is rather more radical, where initiatives have been taken to find
out novel avenues, both for production and application of spin-polarized currents.
In this direction, research effort has been focussed on the spin transport in semiconductors to explore whether semiconductors can operate both as spin polarizers
and spin valves. The significance of this attempt is that amplification of signal can
be obtained in semiconductor-based spintronic devices, which could in principle
function as multifunctional devices. Although the existing metal-based devices are
successful as switches or valves, they do not amplify signals. A more important point
is that such semiconductor-based devices are expected to be much easily integrated
with conventional semiconductor industry. In order to effectively include spins into
existing semiconductor-based devices, the technical challenges to achieve are efficient injection of electron spins followed by their transport into the device; finally
controlling, manipulation and detection of this spin-polarized currents.
In this direction, spintronics has also extended its attention in the field of semiconductor devices, such as spin-FET, spin transistor, magnetic semiconductor devices
etc. Very recently, advancement in the field of materials engineering presents a
promising scenario to realize spintronic devices based on optical spin manipulation. Furthermore, application of electron and nuclear spins for quantum information processing and quantum computation has invoked tremendous ambition to the
researcher. In fact, among many proposed hardware of quantum computer, the ones
based on electron and nuclear spins have gained appreciable attentions. Evidently,
spins of electrons and spin-1/2 nuclei could be perfect candidates for realization
of quantum bits (qubits) given that their Hilbert spaces are well-defined and their
decoherence is relatively slow.
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manner. In this direction, spin relaxation and transport in both metallic and semiconducting samples are subject of intense research interest, not only for issues related to
fundamental solid-state physics but also for their potential in electronic technology.
Designing and manufacturing of spintronic devices are executed by two different
approaches. The first approach is to achieve improvement in the existing giantmagnetoresistive (GMR)-based technology. In this direction, a very preliminary
attempt is to explore new materials having even larger electron spin polarization.
Another attempt includes improving upon the existing GMR devices in order to
obtain better spin filtering. In GMR-based industry, the already existing operational prototype device is the read head and memory storage cell. This is basically a
GMR sandwich structure, consisting of alternating ferromagnetic and non-magnetic
metallic layers. It is the relative magnetizations alignment in the adjacent ferromagnetic layers that decide the device resistance. For instance, device resistance is
small for parallel alignment of magnetizations, whereas it is large for antiparallel
alignment. Such change in resistance, referred to as magnetoresistance, is utilized to
sense variations in magnetic fields. In recent efforts, magnetic tunnel junction-based
devices have also been involved in GMR technology. In magnetic tunnel junctions,
tunnelling current depends on the orientations of magnetizations of the electrodes.
The second approach is rather more radical, where initiatives have been taken to find
out novel avenues, both for production and application of spin-polarized currents.
In this direction, research effort has been focussed on the spin transport in semiconductors to explore whether semiconductors can operate both as spin polarizers
and spin valves. The significance of this attempt is that amplification of signal can
be obtained in semiconductor-based spintronic devices, which could in principle
function as multifunctional devices. Although the existing metal-based devices are
successful as switches or valves, they do not amplify signals. A more important point
is that such semiconductor-based devices are expected to be much easily integrated
with conventional semiconductor industry. In order to effectively include spins into
existing semiconductor-based devices, the technical challenges to achieve are efficient injection of electron spins followed by their transport into the device; finally
controlling, manipulation and detection of this spin-polarized currents.
In this direction, spintronics has also extended its attention in the field of semiconductor devices, such as spin-FET, spin transistor, magnetic semiconductor devices
etc. Very recently, advancement in the field of materials engineering presents a
promising scenario to realize spintronic devices based on optical spin manipulation. Furthermore, application of electron and nuclear spins for quantum information processing and quantum computation has invoked tremendous ambition to the
researcher. In fact, among many proposed hardware of quantum computer, the ones
based on electron and nuclear spins have gained appreciable attentions. Evidently,
spins of electrons and spin-1/2 nuclei could be perfect candidates for realization
of quantum bits (qubits) given that their Hilbert spaces are well-defined and their
decoherence is relatively slow.