Espintronica
www.micromagnetics.com
www.directvacuum.com
Micro Magnetics, Inc.
421 Currant Road
Fall River, MA 02720
Phone: (508)672‐4489
Fax: (508)672‐0059
admin@micromagnetics.com
What is Spintronics? a.k.a Magnetoelectronics, Spin
Electronics, or Spin‐based Electronics.
The age of electrically‐based devices has been with us for more than six decades. With more and
more electrical devices being packed into smaller and smaller spaces, the limits of physical space will
prevent further expansion in the direction the microelectronics industry is currently going. Also, volatile
memory, which does not retain information upon being powered off, is significantly hindering ultrafast
computing speeds. However, a new breed of electronics, dubbed “spintronics,” may change all of that.
Instead of solely relying on the electron’s negative charge to manipulate electron motion or to store
information, spintronic devices would further rely on the electron’s spin degree of freedom, the
mathematics of which is similar to that of a spinning top. Since an electron’s spin is directly coupled to
its magnetic moment, its manipulation is intimately related to applying external magnetic fields. The
advantage of spin‐based electronics is that they are very nonvolatile compared to charge‐based
electronics, and quantum‐mechanical computing based on spintronics could achieve speeds unheard of with conventional electrical computing. Spintronics, also called magnetoelectronics, spin electronics, or
spin‐based electronics, is an emerging scientific field. The research on spintronics can be divided into the
following subfields.
Spin Valve with Giant Magnetoresistance
One spintronic device that currently has wide commercial application is the spin‐valve. Most
modern hard disk drives employ spin‐valves to read each magnetic bit contained on the spinning
platters inside. A spin‐valve is essentially a spin “switch” that can be turned on and off by external
magnetic fields. Basically, it is composed of two ferromagnetic layers separated by a very thin non‐
ferromagnetic layer. When these two layers are parallel, electrons can pass through both easily, and
when they are antiparallel, few
electrons will penetrate both layers.
The principles governing spin‐valve
operation are purely quantum
mechanical. Generally, an electron
current contains both up and down spin
electrons in equal abundance. When
these electrons approach a magnetized
ferromagnetic layer, one where most or
all contained atoms point in the same
direction, one of the spin polarizations
will scatter more than the other. If the ferromagnetic layers are parallel, the electrons not scattered by
the first layer will not be scattered by the second, and will pass through both. The result is a lower total resistance (large current). However, if the layers are antiparallel, each spin polarization will scatter by
the same amount, since each encounters a parallel and antiparallel layer once. The total resistance is
then higher than in the parallel configuration (small current).
www.micromagnetics.com
www.directvacuum.com
Micro Magnetics, Inc.
421 Currant Road
Fall River, MA 02720
Phone: (508)672‐4489
Fax: (508)672‐0059
admin@micromagnetics.com
Thus, by measuring the total resistance of the spin valve, it is possible to determine if it is in a
parallel or antiparallel configuration, and since this is controlled by an external magnetic field, the ...
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