The eigenvectors of the Pauli spin matrices are examples of SPINORS which are 2×1 column vectors that represent the spin state of an electron. If the SPINORS associated with an electron in a given state is known, then one can easily deduce the electron's spin orientation.

The beginning of spintronics:

Although "spin" plays a fundamental role in explaining the multiplicity of atomic spectra, this is not its most important role. While magnetism remains the domain of spin, in the late 20^th century, it was realized that the spin alone or in conjunction with charge, can be exploited to process information, particularly digital information encoded with the binary bits 0 and 1, which is the central theme in the field of spintronics. Early successes in this area include the development of magnetic read heads for sensing massive dense magnetic storage media (Hard Disk Drive), non-volatile magnetic random access memory, programmable spintronic logic devices, rotational speed control system, positioning control devices in robotics, perimeter defense systems, magnetometers, etc. On the other hand, the application of spintronics in information technology, particularly for computing and signal processing is relatively a new field.

The more essential branch of spintronics is monolithic spintronics, where charge has no direct role and information is encoded entirely in the spin polarization of a single electron, which is made to have only two values: spin up and spin down. The ultimate performance of spintronic computing circuits is spin-based quantum computers, which dissipate no energy at all to complete a logic operation since they operate on the basis of reversible quantum dynamics. Therefore, understanding the science and technology of spintronics has become imperative for the students of basic science and engineering disciplines.

References:

[1]. J.J. Sakurai, Modern quantum mechanics, Pearson Education in South Asia, 1994.

Quiz 2:

(Q2.1). What happens to the out coming beams, if we change the non-uniform magnetic field into uniform magnetic field in the Stern-Gerlach experiment?
(Q2.2). What are SPINORS? How one can use SPINORS to deduce the electron's spin orientation?
(Q2.3). In quantum mechanics, how does a physical quantity expressed in Heisenberg's mechanics and in Schrodinger's wave mechanics?
(Q2.4). Show that the spin angular momentum operators satisfy the commutation relation!