| Grant number: | 99/10359-7 |
| Support Opportunities: | Research Projects - Thematic Grants |
| Start date: | June 01, 2000 |
| End date: | May 31, 2008 |
| Field of knowledge: | Physical Sciences and Mathematics - Physics - Condensed Matter Physics |
| Principal Investigator: | Nei Fernandes de Oliveira Junior |
| Grantee: | Nei Fernandes de Oliveira Junior |
| Host Institution: | Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil |
| Pesquisadores principais: | Andre Bohomoletz Henriques |
| Associated scholarship(s): | 98/11522-6 - New investigations using magnetization-step method., BP.PD |
Abstract
It is proposed a research program on semiconductors involving mostly low-temperatures and high magnetic fields, the main resources of the LESBT. This program provides continuation for already existent projects on magnetic interactions in bulk samples of Diluted Magnetic Semiconductors (DMS) and electric and optical properties in III-V bidimensional structures, and starts a new project in MBE-produced IV-VI materials. In DMS it is proposed the continuation of the investigation on the distant neighbors exchange interactions following our pioneer work on the ZnMnX (X=S, Se and Te) series. In this work it was measured for the first time a sequence of exchange constants up to 5th neighbors and the results are in strong disagreement with the existent theoretical predictions. We propose to investigate the series CdMnX, and also materials containing Co. The objective is to establish, for the first time, series of exchange constants between distant neighbors to stimulate new theoretical work and consequently a better understanding to the mechanisms of the interaction. We propose also to investigate (via magnetization steps) the-anisotropy of the exchange interaction in DMS such as PbCeS and PbCeSe. Another program is the investigation of magnetization steps in IV-VI bulk compounds, continuing the investigations started with PbEuX. We intend to substitute Eu by Mn and Gd in PbX, and to study also SnTe with Eu and Gd. The samples for the above research will come from our partner Z. Galacki, from Poland. The present studies in III-V structures are concentrated in doped super-lattices aiming at high mobility systems. We intend to optimize the results already obtained, and in a next step, to develop and investigate super-lattices of remote doping, which present some peculiar properties. We propose to design, fabricate (by MOCVD at CETUC-PUCARJ, also at CPQD-LNLS, and by NLBE at IFUSP) and characterize several types of these super-lattices varying the structure parameters. We intend, in parallel, to develop theoretical studies using various types of approximations to interpret the results. The objective of the program is to develop super-lattices of high mobility, develop theoretical methods to describe the interactions, and study many-body effects in a system of degenerated electrons with dimnesionality between 2 and 3. For the research in the IV-VI materials we are associating with a group of the Laboratório de Materiais e Sensores of INPE which operates an NIBE growing PbTe and SnTe with Eu and eventually Mn. This group bas strong support from Prof G. Bauer (and his group) from the University of Linz in Austria... (AU)
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