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1 An Overview of Spintronics
trical properties and different electric resistance. This leads to one of the interesting
applications of ferromagnetic material, that is to read and store information using
this magnetoresistance effect.
1.8 Functionality of ‘Spin’ in Spintronics
Electrons have much more functionality than merely causing the current flow.
Successful utilization of their spins may open up several new possibilities. It is well
known that the spin is a quantum-mechanical property, which is depicted by a rotation, either clockwise or anticlockwise, around its own axis. This in turn gives rise
to a magnetic moment. Therefore, the electron may be regarded as a minute magnet
in which either the magnetic North or South Pole are supposed to points upwards,
which gives rise to spin-up or spin-down condition of electrons. Consequently, electron spins could be controlled by applying an external magnetic field in a systematic
manner. Electronic spins also play vital role in determining the magnetic properties
of a material. Utilizing this phenomenon in spintronics, the goal is to control and
manipulate spin-polarized transport through ferromagnetic contacts for information
processing and other applications. The proposed usage of electronic states, representing only 0 or 1, within a semiconductor is purely binary. In that case, the range of
eight bits can represent every number between 0 and 255, but only one number at a
time. In a different approach, the ‘spin-up’ and ‘spin-down’ states can be represented
as superposition of 0 or 1, which are referred to as spintronics quantum bits, and
are also known as qubits. Qubits can represent every number between 0 and 255
simultaneously.
1.8.1 Basic Principle of Working of All Spintronic Devices
(Simple Scheme)
• The information is written and stored in the particular spin orientations, i.e., either
in up- or in down-spin directions.
• Information is transferred along the wire through spins attached to mobile
electrons.
• Finally, information is captured and read at a terminal where mobile electrons
are being collected. Most importantly, spin polarization of conduction electrons
survives in the nanoseconds time scale. This lifetime of electron spin orientation is
relatively long compared to tens of femtoseconds, during which momentum of the
conduction electron decays. This makes spintronic devices potential candidates
for memory storage and magnetic sensors applications, and, also particularly
advantageous for quantum computing where electron spin would represent ‘qubit’
of information.
1 An Overview of Spintronics
trical properties and different electric resistance. This leads to one of the interesting
applications of ferromagnetic material, that is to read and store information using
this magnetoresistance effect.
1.8 Functionality of ‘Spin’ in Spintronics
Electrons have much more functionality than merely causing the current flow.
Successful utilization of their spins may open up several new possibilities. It is well
known that the spin is a quantum-mechanical property, which is depicted by a rotation, either clockwise or anticlockwise, around its own axis. This in turn gives rise
to a magnetic moment. Therefore, the electron may be regarded as a minute magnet
in which either the magnetic North or South Pole are supposed to points upwards,
which gives rise to spin-up or spin-down condition of electrons. Consequently, electron spins could be controlled by applying an external magnetic field in a systematic
manner. Electronic spins also play vital role in determining the magnetic properties
of a material. Utilizing this phenomenon in spintronics, the goal is to control and
manipulate spin-polarized transport through ferromagnetic contacts for information
processing and other applications. The proposed usage of electronic states, representing only 0 or 1, within a semiconductor is purely binary. In that case, the range of
eight bits can represent every number between 0 and 255, but only one number at a
time. In a different approach, the ‘spin-up’ and ‘spin-down’ states can be represented
as superposition of 0 or 1, which are referred to as spintronics quantum bits, and
are also known as qubits. Qubits can represent every number between 0 and 255
simultaneously.
1.8.1 Basic Principle of Working of All Spintronic Devices
(Simple Scheme)
• The information is written and stored in the particular spin orientations, i.e., either
in up- or in down-spin directions.
• Information is transferred along the wire through spins attached to mobile
electrons.
• Finally, information is captured and read at a terminal where mobile electrons
are being collected. Most importantly, spin polarization of conduction electrons
survives in the nanoseconds time scale. This lifetime of electron spin orientation is
relatively long compared to tens of femtoseconds, during which momentum of the
conduction electron decays. This makes spintronic devices potential candidates
for memory storage and magnetic sensors applications, and, also particularly
advantageous for quantum computing where electron spin would represent ‘qubit’
of information.