Ferromagnetism of Co, Eu Co-doped ZnO and 5%-Co doped TiO2 magnetic semiconductors
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Date
2014-02-04
Journal Title
Journal ISSN
Volume Title
Publisher
Australian Institute of Physics
Abstract
Diluted magnetic semiconductor has attracted wide interest due to its potential applications in spintronics devices. Oxide semiconductor based diluted magnetic semiconductors has been investigated in detail for possible ferromagnetism above room temperature. However, most of the diluted magnetic semiconductors show very weak ferromagnetism. The magnetic moment is originated from the doped magnetic element, such as Fe, Co, Ni. Rare-earth element, which shows strong spin-orbit coupling, may enhance the magnetic anisotropy of the diluted magnetic semiconductors, thus enhances the ferromagnetism. In this work, we used both Co and Eu to co-dope ZnO and deposited Co doped TiO2 thin films in order to achieve a diluted room-temperature magnetic semiconductor with strong ferromagnetism. 4%Co and 4%Eu or 6% Eu were used for the doping by implantation in ZnO and 5%Co-TiO2 film were deposited on LaAlO3 substrate under different oxygen partial pressures from 10-4 to 10-6 torr. For the ZnO-based thin films, XRD analysis indicates there is no secondary or impurity phase. Magnetic measurement by SQUID shows room temperature ferromagnetism. Polarized neutron reflectometry (PNR) analysis illustrates that ZnO film is 100 nm in thickness and the magnetic layers is around 30 nm, which is in consistent with the penetration depth of Co and Eu implantation, indicating the magnetic moment is due to the Co and Eu co doping. 4%Co, 4%Eu codoped ZnO film has a saturation magnetization of 3.57 emu/cm3, while 4%Co, 6%Eu co doped ZnO film has a saturation magnetization of 9.62 emu/cm3, indicating the significant enhancement of saturation magnetization by more rare earth element doping. For the TiO based thin films, XRD analysis show epitaxial growth and that the films have anatase phases. TEM confirms the single crystal like microstructure. EDX mapping indicates that Co is uniformly distributed in the TiO2 matrix, suggesting effective doping of Co dopant. Magnetic measurement shows that film deposited under lower oxygen partial pressure has a larger saturation magnetization. PNR shows that the magnetization is uniformly distributed along the film thickness. The magnetization for the film deposited under an oxygen partial pressure of 10-6 torr is about 4.2 emu/cm3, which is much smaller than that measured by SQUID (30 emu/cm3). This suggests a magnetic dead layer on the film surface.
Description
Keywords
Chalcogenides, Crystal growth methods, Elements, Films, Materials, Metals, Oxides, Oxygen compounds, Rare earths, Semiconductor materials, Titanium compounds, Transition elements, Transition element compounds, Zinc compounds
Citation
Lee, O. J., Luo, X., Lee, W. T., Lauter, V., Triani, G., Li, S., & & Yi, J, B. (2014). Ferromagnetism of Co, Eu Co-doped ZnO and 5%-Co doped TiO2 magnetic semiconductors. Poster presented to the 38th Annual Condensed Matter and Materials Meeting 2014, Waiheke Island Resort, Waiheke, Auckland, New Zealand 4th February - 7th February, 2014. Retrieved from: https://physics.org.au/wp-content/uploads/cmm/2014/Wagga2014proceedings.pdf