Loading...
Please wait, while we are loading the content...
VIBRATION DOS OF Fe DOPED INTO RUTILE Sn (Sb) OXIDE
| Content Provider | Semantic Scholar |
|---|---|
| Author | Nomura, Kiyoshi Rykov, Alexandre I. Németh, Zoltán Yoda, Yoshitaka |
| Copyright Year | 2011 |
| Abstract | [Introduction] Transparent diluted magnetic oxide seiconductors (DMS), which show ferromagnetism at room temperature, are expected to be one of the most intriguing spintronics materials. Ferromagnetic behavior can occur as an impact of low concentration of doped magnetic atoms on wide gap semiconductors. The ferromagnetism is presumed to be induced either due to the spin arrangement of magnetic atoms through localized spins trapped in oxygen vacancies or due to formation of precipitated magnetic clusters. It is necessary to reveal how the dilute or clustered ferromagnetic atoms are involved into metal oxide semiconductor. We have measured nuclear resonant inelastic scattering (NIS) of metal oxides using synchrotron radiation, and revealed that NIS is useful for determination of dilution or cluster formation of doped ions [1]. The co-doping of SnO2 with Sb and Fe improves electrical conductivity and magnetism. Sb ions enhance the solubility of Fe ions in SnO2, widening the possibilities of enhancing the physical properties of cassiterite based materials [2]. Zn doping effect are studied [3]. In this study, we determine local vibration density of state (VDOS) distribution of Fe doped in various Fe and Sb doped Sn oxides. [Experimental] Samples of Fe and Sb doped SnO2-δ with Zn (less than 30 %) were obtained by a sol-gel method. SnCl2·2H2O, SbCl3, ZnO, and metallic Fe with abundant Fe were dissolved by using HCl or HNO3 and citric acid. Each solution was mixed according to the nominal amounts of compounds, and completed with ethylene glycol. The proper amount of enriched Fe was mixed into natural abundant Fe solution to adjust into about 2% Fe content. These solutions were condensed at 80-90 oC and decomposed at 250 oC during 2 hours. The xerogel was oxidized in air at 550 oC for 1 hour, and, after milling, the powders were finally annealed at 550 oC for 1 hour. Mössbauer spectra were measured by using Co(Cr) and calibrated using α-Fe foil. NIS spectra were measured in SPring8, using BL09, of which the energy resolution was 2.5 meV. Phonon DOS were calculated from NIS spectra. [Results and discussion] It is confirmed from XRD patterns that the main rutile structure of 10% Sb and 20% Fe-doped tin oxide has been kept up to additionally 10% doping of non-magnetic Zn ions. Sb plays a role of stabilization of rutile structure of SnO2 and induction of carrier density. Zn oxide seems to be dissolved in SnO2, and not well crystallized at Zn concentrations less than 10%. At more than 10% Zn concentration, the impurity of Zn compounds such as ZnFe2O4 was clearly detected by XRD. The magnetization increased with doping Zn from 1% to 7%. The magnetic splitting components in Mossbauer spectra are related with the intensity of magnetization in the range of less than 10% Zn doping rates. It is an interesting phenomenon that magnetic exchange of Fe ions increases with dilution by nonmagnetic Zn ions. The results suggest that there are many defects produced between tin oxides and zinc oxides. From the analysis of NIS spectra it is found that even VDOS of 20% Fe doped in SnO2 (10% Sb) resembles Sn VDOS of tin oxide itself although the distribution was a little expanded as shown in figure 1. When doping Zn into the tin oxides, the VDOS distributions around 1520 meV were a little increased, which suggested small contents of non magnetic nano particles such as ZnFe2O4. The large saturation magnetization observed was estimated due to dilution of Fe into rutile structure rather than formation of precipitated magnetic iron oxides. Therefore, magnetic components in Mössbauer spectra are not due to high-purity maghemite but to spin arrangement of dispersed iron ions. We concluded the followings; high doping of 20% Fe in 10% Sb doped SnO2 is possible. Zn doping may make many defects at the interface between SnO2 and Zn compounds. VDOS can suggest that the magnetism observed at the range of less than 10% Zn doping is due to dilution, not to precipitation of magnetic oxides. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://anzen.t.u-tokyo.ac.jp/~nomura/nomura/icame2011SnO2NISnomura1.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
