arXiv subjects

Tomasz Dietl

Publications and source records attributed to Tomasz Dietl.

58 records · Page 4Linked to original sources

arXiv2003

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.

cond-mat.mtrl-sci↗

arXiv2002

Why ferromagnetic semiconductors?

Rapid development of information technologies originates from the exponential increase in the density of information that can be processed, stored, and transfer by the unit area of relevant devices. There is, however, a growing amount of evidences that the progress achieved in this way approaches its limits. Various novel ideas put forward to circumvent barriers ahead are described. Particular attention is paid to those concepts which propose to exploit electron or nuclear spins as the information carriers. Here, ferromagnetic semiconductors of III-V or II-VI compounds containing a sizable concentration of transition metals appear as outstanding spintronic materials.

cond-mat.mtrl-sci↗

arXiv2002

Ferromagnetic semiconductors

The current status and prospects of research on ferromagnetism in semiconductors are reviewed. The question of the origin of ferromagnetism in europium chalcogenides, chromium spinels and, particularly, in diluted magnetic semiconductors is addressed. The nature of electronic states derived from 3d of magnetic impurities is discussed in some details. Results of a quantitative comparison between experimental and theoretical results, notably for Mn-based III-V and II-VI compounds, are presented. This comparison demonstrates that the current theory of the exchange interactions mediated by holes in the valence band describes correctly the values of Curie temperatures T_C magnetic anisotropy, domain structure, and magnetic circular dichroism. On this basis, chemical trends are examined and show to lead to the prediction of semiconductor systems with T_C that may exceed room temperature, an expectation that are being confirmed by recent findings. Results for materials containing magnetic ions other than Mn are also presented emphasizing that the double exchange involving hoping through d states may operate in those systems.

cond-mat.mtrl-sci↗

arXiv2000

Ferromagnetism in III-V and II-VI semiconductor structures

The current status of research on the carrier-mediated ferromagnetism in tetrahedrally coordinated semiconductors is briefly reviewed. The experimental results for III-V semiconductors, where Mn atoms introduce both spins and holes, are compared to the case of II-VI compounds, in which the ferromagnetism has been observed for the modulation-doped p-type Cd1-xMnxTe/Cd1-y-zMgyZnzTe:N heterostructures, and more recently, in Zn1-xMnxTe:N epilayers. On the theoretical side, a model is presented, which takes into account: (i) strong spin-orbit and kp couplings in the valence band; (ii) the effect of confinement and strain upon the hole density-of-states and response function, and (iii) the influence of disorder and carrier-carrier interactions, particularly near the metal-to-insulator transition. A comparison between experimental and theoretical results demonstrates that the model can describe the magnetic circular dichroism, the values of TC observed in the studied systems as well as explain the directions of the easy axis and the magnitudes of the corresponding anisotropy fields as a function of confinement and biaxial strain. Various suggestions concerning design of novel ferromagnetic semiconductor systems are described.

cond-mat.mtrl-sci↗