Knowing that all moving charges produce magnetic fields, they proposed to measure the magnetic fields produced by the electrons orbiting nuclei in atoms. Much to their surprise, however, the two physicists found that electrons themselves act as if they are spinning very rapidly, producing tiny magnetic fields independent of those from their orbital motions.
Soon the terminology 'spin' was used to describe this apparent rotation of subatomic particles. It is analogous to the spin of a planet in that it gives a particle angular momentum and a tiny magnetic field called a magnetic moment. Based on the known sizes of subatomic particles, however, the surfaces of charged particles would have to be moving faster than the speed of light in order to produce the measured magnetic moments.
Furthermore, spin is quantized, meaning that only certain discrete spins are allowed. This situation creates all sorts of complications that make spin one of the more challenging aspects of quantum mechanics. Spin is likewise an essential consideration in all interactions among subatomic particles, whether in high-energy particle beams, low-temperature fluids or the tenuous flow of particles from the sun known as the solar wind.
Indeed, many if not most physical processes, ranging from the smallest nuclear scales to the largest astrophysical distances, depend greatly on interactions of subatomic particles and the spins of those particles. Stenger, professor of physics at the University of Hawaii at Manoa, offers another, more technical perspective: "Spin is the total angular momentum, or intrinsic angular momentum, of a body.
The spins of elementary particles are analogous to the spins of macroscopic bodies. In fact, the spin of a planet is the sum of the spins and the orbital angular momenta of all its elementary particles. At the same time, it would amplify the flow of spin-down electrons so that it directly opposed the flow of the spin-up ones.
Because equal numbers of electrons moved in opposite directions, no net electrical current flowed across the surface. However, because a spin-up electron moving to the right has the same effect as a spin-down electron moving to the left, the flows of spin reinforced each other, leading to a pure spin current.
The two teams used different optical techniques to spot the spin-only currents, which flowed for only a few nanometers. The experiments nicely confirm predictions made in the s, says David Awschalom of the University of California, Santa Barbara. Chiral crystals can produce spin-polarized currents that propagate over tens of micrometers—a promising feature for application in spintronics devices.
Read More ». Inside a quantum spin ice, the constant that defines electromagnetic interactions is 10 times larger than normal, according to calculations. Adding a friction term to models helps them better account for how spin textures evolve experimentally at room temperature.
Induction and Magnetic Recording. Classical views of the a orbital motion and b spin of an electron. As atomic physics and chemistry began to explain the periodic table with the help of the Bohr model of the atom in the early s, magnetic properties were assigned to the electrons in atoms. Electrons appeared to exhibit two types of motion in an atom: orbital and spin. Orbital motion referred to the motion of an electron around the nucleus of the atom.
Since a charged particle was moving, a magnetic field was created. But electrons and protons and other particles also appeared to be spinning around their centers, creating yet another magnetic field.
The magnetic field due to the orbital motion and the magnetic field due to the spin could cancel or add, but expressions for the exact coupling between the two are too complicated to go into here. Since electrons were moving and spinning within atoms, ferromagnetism could now be explained by the motion of charges within different materials.
If all of the electrons in an object line up with their spins in the same direction, the spins will add and create an observable field.
That last sentence is slightly unrealistic. Solids contain incredably large numbers of electrons, and they will never all completely line up. Instead, a solid generally consists of magneticdomains. Also in Oil and petroleum products explained Oil and petroleum products Refining crude oil Where our oil comes from Imports and exports Offshore oil and gas Use of oil Prices and outlook Oil and the environment.
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