2,016 research outputs found
How to make semiconductors ferromagnetic: A first course on spintronics
The rapidly developing field of ferromagnetism in diluted magnetic
semiconductors, where a semiconductor host is magnetically doped by transition
metal impurities to produce a ferromagnetic semiconductor (e.g. Ga_{1-x}Mn_xAs
with x ~ 1-10 %), is discussed with the emphasis on elucidating the physical
mechanisms underlying the magnetic properties. Recent key developments are
summarized with critical discussions of the roles of disorder, localization,
band structure, defects, and the choice of materials in producing good magnetic
quality and high Curie temperature. The correlation between magnetic and
transport properties is argued to be a crucial ingredient in developing a full
understanding of the properties of ferromagnetic semiconductors.Comment: 8 pages; to appear in the special issue 'Quantum Phases at Nanoscale'
of Solid State Communication
Dissipationless transport in low density bilayer systems
In a bilayer electronic system the layer index may be viewed as the
z-component of an isospin-1/2. An XY isospin-ordered ferromagnetic phase was
observed in quantum Hall systems and is predicted to exist at zero magnetic
field at low density. This phase is a superfluid for opposite currents in the
two layers. At B=0 the system is gapless but superfluidity is not destroyed by
weak disorder. In the quantum Hall case, weak disorder generates a random gauge
field which probably does not destroy superfluidity. Experimental signatures
include Coulomb drag and collective mode measurements.Comment: 4 pages, no figures, submitted to Phys. Rev. Let
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