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Title: Fabrication and characterization of nanostructured half- metals and diluted magnetic semiconductors
Keywords: spintronics, nanostructured, half metals, diluted magnetic semiconductors, magnetic properties, electrical transport properties,
Issue Date: 12-Jun-2007
Citation: LI HONGLIANG (2007-06-12). Fabrication and characterization of nanostructured half- metals and diluted magnetic semiconductors. ScholarBank@NUS Repository.
Abstract: The performance of existing metal-based spintronic devices is limited primarily by two factors: low spin polarization of the ferromagnetic materials used to build the devices and difficulties with the control of charge transport in metals. The main objectives of this work are to grow and characterize two types of promising materials for future spintronic devices: Fe3O4 and Ge1-xMnx. The former is a kind of half metals that offer 100% polarization and the latter a Ge-based diluted magnetic semiconductor which has the possibility to be integrated with the Si devices. Our work on Fe3O4 was focused on the effect of antiphase boundary on its electrical transport properties. Through detailed dynamic conductance measurements, we were able to reveal that the poor performance of Fe3O4-based spintronic devices obtained so far was mainly caused by the low average polarization due to the existence of randomly distributed antiphase boundaries. The work on Ge1-xMnx was focused on understanding of the origin of ferromagnetism in this material system. Amorphous Ge1-xMnx thin films with or without secondary phases, granular thin films, and I'-doped amorphous thin films have been fabricated and characterized. In spite of the large structural differences, one common result observed for these materials was that the T*C values were very close to those reported for epitaxially grown samples. This suggested that the so-called Curie temperature reported in literature was not an indicator of global ordering but rather the ordering temperature of magnetic clusters in the Ge1-xMnx system.
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