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Posts Tagged ‘campo magnético’

Magnetization vector manipulation by electric fields
D. Chiba, M. Sawicki, Y. Nishitani, Y. Nakatani, F. Matsukura & H. Ohno

Conventional semiconductor devices use electric fields to control conductivity, a scalar quantity, for information processing. In magnetic materials, the direction of magnetization, a vector quantity, is of fundamental importance. In magnetic data storage, magnetization is manipulated with a current-generated magnetic field (Oersted–Ampère field), and spin current is being studied for use in non-volatile magnetic memories. To make control of magnetization fully compatible with semiconductor devices, it is highly desirable to control magnetization using electric fields. Conventionally, this is achieved by means of magnetostriction produced by mechanically generated strain through the use of piezoelectricity. Multiferroics have been widely studied in an alternative approach where ferroelectricity is combined with ferromagnetism. Magnetic-field control of electric polarization has been reported in these multiferroics using the magnetoelectric effect, but the inverse effect—direct electrical control of magnetization—has not so far been observed. Here we show that the manipulation of magnetization can be achieved solely by electric fields in a ferromagnetic semiconductor, (Ga,Mn)As. The magnetic anisotropy, which determines the magnetization direction, depends on the charge carrier (hole) concentration in (Ga,Mn)As. By applying an electric field using a metal–insulator–semiconductor structure, the hole concentration and, thereby, the magnetic anisotropy can be controlled, allowing manipulation of the magnetization direction.

Texto completo em http://www.nature.com/nature/journal/v455/n7212/full/nature07318.html
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Nanoscale magnetic sensing with an individual
electronic spin in diamond

Detection of weak magnetic fields with nanoscale spatial resolution
is an outstanding problem in the biological and physical
sciences. For example, at a distance of 10 nm, the spin of a single
electron produces a magnetic field of about 1 mT, and the corresponding
field from a single proton is a few nanoteslas. A sensor
able to detect such magnetic fields with nanometre spatial resolution
would enable powerful applications, ranging from the detection
of magnetic resonance signals from individual electron or
nuclear spins in complex biological molecules to readout of classical
or quantum bits of information encoded in an electron or
nuclear spin memory. Here we experimentally demonstrate an
approach to such nanoscale magnetic sensing, using coherent
manipulation of an individual electronic spin qubit associated
with a nitrogen-vacancy impurity in diamond at room temperature.
Using an ultra-pure diamond sample, we achieve detection
of 3 nT magnetic fields at kilohertz frequencies after 100 s of averaging.
In addition, we demonstrate a sensitivity of 0.5 mTHz1/2 [microtesla.(Hz na potência -1/2)]
for a diamond nanocrystal with a diameter of 30 nm.
Este artigo de J. R. Maze et al. e outros sobre nanomagnetismo encontram-se em: http://www.nature.com/nature/journal/v455/n7213.

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