Magnetic uniformity of oxide based diluted magnetic semiconductors

19^th World Congress on Materials Science and Engineering

June 11-13, 2018 | Barcelona, Spain

Jiabao Yi

UNSW, Australia,

Posters & Accepted Abstracts: J Material Sci Eng

Abstract :

Diluted magnetic semiconductor is one of the materials for spintronic devices. Oxide based diluted magnetic semiconductors have attracted extensive interest due to its possible high Curie temperature. Intrinsic ferromagnetism is essential for the practical applications. However, currently, the intrinsic ferromagnetism in oxide diluted magnetic semiconductors is difficult to be determined. One of the popular ways is to use transmission electron microscopy, electron dispersive energy spectroscopy (EDS) and electron energy loss spectroscopy to identify the uniform distribution of dopants and whether there are no clusters. However, there is no direct evidence to show the magnetic uniformity in oxide based diluted magnetic semiconductors. Recently, we used low energy muon spin relaxation approach to identify the magnetic uniformity in Co doped TiO2, Fe doped In2O3 and Co doped ZnO systems. Combined with other techniques, such as TEM EDS and measurement by magnetometer, we found that Co doped TiO2 is intrinsic with magnetic uniformity when Co doped TiO2 was deposited with relative high rate under an oxygen partial pressure of 10-6 torr. The uniformity will disappear if the deposition rate is relatively low. For Co doped ZnO, the samples deposited under different oxygen partial pressures does not induce clustering or secondary phase. Dopants are uniformly distribution in the ZnO host. However, muon spin relaxation measurement indicates that the samples do not show magnetic uniformity. Bound magnetic polarons formation is the origin of ferromagnetism, supported by resistance measurement. For Fe doped In2O3, clusters are observed in the sample deposited under an oxygen partial pressure of 10-7 torr. X-ray absorption spectroscopy indicate the clusters are Fe3O4, but on metallic Fe. In addition, muon spin relaxation and polarized neutron diffraction all indicate the Fe doped In2O3 via substitution dominates the contribution of ferromagnetism and the magnetization is higher than Fe3O4 clusters, suggesting that clustering is not the major origin of ferromagnetism. The work has shown that the mechanisms of different oxide based diluted magnetic semiconductor may be varied. We have to investigate one by one. jiabao.yi@unsw.edu.au