6,163 research outputs found
Spin order manipulations in nanostructures of II-VI ferromagnetic semiconductors
An overview of recent studies on ferromagnetism in Cr- and Mn-based II-VI
diluted magnetic semiconductors is presented emphasizing differences in
underlying exchange mechanisms. Examples of manipulations with spin ordering by
carrier density, dimensionality, light, and electric field are given.Comment: 6 pages, 7 figures, Proceedings International Conference on
Magnetism, Rome 2003, J. Magn. Magn. Mater., in pres
Hans Sachs’ Tristrant : farce, tragedy or serious doctrine?
When at the end of Hans Sachs' tragedy of Tristrant, dated February 7th, 1553, the herold takes the floor, he calls to the audience to recognize that this is a tragedy, Auß der wird offentlich erkendt, Wie solche unorndliche lieb Hat so ein starck mechtigen trieb, Wo sie einnimbt ein junges hertz Mit bitter angst, senenden schmertz, Darinn sie also heftig wüt, Verkert hertz, sin, vernunft und gmüt, Wird leichtfertig, verwegen gantz, Schlecht seel, lieb, ehr, gut in die schantz, Acht fürbas weder sitten noch tugent, (184,32-185,3) (1) ...
III-V and II-VI Mn-based Ferromagnetic Semiconductors
A review is given of advances in the field of carrier-controlled
ferromagnetism in Mn-based diluted magnetic semiconductors and their
nanostructures. Experimental results for III-V materials, where the Mn atoms
introduce both spins and holes, are compared to the case of II-VI compounds, in
which the Curie temperatures T_C above 1 K have been observed for the uniformly
and modulation-doped p-type structures but not in the case of n-type films. The
experiments demonstrating the tunability of T_C by light and electric field are
presented. The tailoring of domain structures and magnetic anisotropy by strain
engineering and confinement is discussed emphasizing the role of the spin-orbit
coupling in the valence band. The question of designing modulated magnetic
structures in low dimensional semiconductor systems is addressed. Recent
progress in search for semiconductors with T_C above room temperature is
presented.Comment: 8 pages, 9 figures, Spring Meeting of the German Physical Society,
March 2003, Advances in Solid State Physic
Origin and control of ferromagnetism in dilute magnetic semiconductors and oxides
The author reviews the present understanding of the hole-mediated
ferromagnetism in magnetically doped semiconductors and oxides as well as the
origin of high temperature ferromagnetism in materials containing no valence
band holes. It is argued that in these systems spinodal decomposition into
regions with a large and a small concentration of magnetic component takes
place. This self-organized assembling of magnetic nanocrystals can be
controlled by co-doping and growth conditions. Functionalities of these
multicomponent systems are described together with prospects for their
applications in spintronics, nanoelectronics, photonics, plasmonics, and
thermoelectrics.Comment: review, 7 pages, 52nd MMM Conference, Tampa Nov. 2007, J. Appl. Phys,
in pres
Refining of metallurgical-grade silicon
A basic requirement of large scale solar cell fabrication is to provide low cost base material. Unconventional refining of metallurical grade silicon represents one of the most promising ways of silicon meltstock processing. The refining concept is based on an optimized combination of metallurgical treatments. Commercially available crude silicon, in this sequence, requires a first pyrometallurgical step by slagging, or, alternatively, solvent extraction by aluminum. After grinding and leaching, high purity qualtiy is gained as an advanced stage of refinement. To reach solar grade quality a final pyrometallurgical step is needed: liquid-gas extraction
Interlayer exchange coupling in (Ga,Mn)As based multilayers
Exhibiting antiferromagnetic interlayer coupling in dilute magnetic
semiconductor multilayers is essential for the realisation of
magnetoresistances analogous to giant magnetoresistance in metallic multilayer
structures. In this work we use a mean-field theory of carrier induced
ferromagnetism to explore possible (Ga,Mn)As based multilayer structures that
might yield antiferromagnetic coupling.Comment: 4 pages, 2 figures. To be published in physica status solidi c as the
proceedings of the PASPS IV conferenc
Magnitude and crystalline anisotropy of hole magnetization in (Ga,Mn)As
Theory of hole magnetization Mc in zinc-blende diluted ferromagnetic
semiconductors is developed relaxing the spherical approximation of earlier
approaches. The theory is employed to determine Mc for (Ga,Mn)As over a wide
range of hole concentrations and a number of crystallographic orientations of
Mn magnetization. It is found that anisotropy of Mc is practically negligible
but the obtained magnitude of Mc is significantly greater than that determined
in the spherical approximation. Its sign and value compares favorably with the
results of available magnetization measurements and ferromagnetic resonance
studies.Comment: 5 pages, 3 figure
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