| Autor: |
Yamahara, H., Seki, M., Adachi, M., Takahashi, M., Nasu, H., Horiba, K., Kumigashira, H., Tabata, H. |
| Předmět: |
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| Zdroj: |
Journal of Applied Physics; 8/14/2015, Vol. 118 Issue 6, p063905-1-063905-7, 7p, 1 Chart, 8 Graphs |
| Abstrakt: |
Carrier-type control of spin-glass (cluster spin-glass) is studied in order to engineer basic magnetic semiconductor elements using the memory functions of spin-glass. A key of carrier-polarity control in magnetite is the valence engineering between Fe(II) and Fe(III) that is achieved by Ti(IV) substitution. Single phases of (001)-oriented Fe3-xTixO4 thin films have been obtained on spinel MgAl2O4 substrates by pulsed laser deposition. Thermoelectric power measurements reveal that Ti-rich films (x?=?0.8) show p-type conduction, while Ti-poor films (x?=?0.6-0.75) show n-type conduction. The systematic Fe(III) reduction to Fe(II) followed by Ti(IV) substitution in the octahedral sublattice is confirmed by the X-ray absorption spectra. All of the Fe3-xTixO4 films (x?=?0.6-0.8) exhibit ferrimagnetism above room temperature. Next, the spin-glass behaviors of Ti-rich Fe2.2Ti0.8O4 film are studied, since this magnetically diluted system is expected to exhibit the spin-glass behaviors. The DC magnetization and AC susceptibility measurements for the Ti-rich Fe2.2Ti0.8O4 film reveal the presence of the spin glass phase. Thermal- and magnetic-field-history memory effects are observed and are attributed to the long time-decay nature of remanent magnetization. The detailed analysis of the time-dependent thermoremanent magnetization reveals the presence of the cluster spin glass state. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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