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Room temperature ferromagnetism in Ti Dioxide DMS
Smekhova, A.; Orlov, A. F.; Balagurov, L. A.; Perov, N. S.; Ganshina, E. A.; Semisalova, A. S.; Novikov, A.; Potzger, K.; Butterling, M.; Cornelius, S.; Yildirim, O.;
Abstract: A detailed study of a room-temperature ferromagnetism in diluted magnetic semiconductors on the basis of Titanium dioxide thin films with incorporated Co and V atoms has been performed. The relations between the structure, magnetization, transport and magneto-optical properties as well as evolution of defects and some peculiarities of preliminary element-specific XANES spectra are presented.
A continues interest to diluted magnetic semiconductors (DMS) during the last decade caused by an ambitious idea to get spin-polarized carriers in transparent semiconductor materials.1 A new physics exhibited by such materials could be exploited in fast developed information processing, storage and other diverse spintronic technologies. Up to now lot of systems have been already studied 2,3,4,5,6; and among them a particular interest to the DMS on the basis of Titanium Dioxide with incorporated 3d impurities (Co, V and Mn) have been ascertained.
The main goal of our present research is the study of the influence of structural properties such as point defects or defect complexes linked to oxygen deficiency on the magnetic, magneto-optical and magneto-transport properties of V (Mn) doped TiO2 anatase thin films. According to preliminary basic researches, magnetism in doped oxides is strongly influenced by defects and represents so far not-understood kind of magnetic phenomenon.
The TiO2 anatase thin films (200÷500 nm) with several percents (3 and 8%) of 3d transition metals with unpaired electrons (Co and V) have been prepared by rf magnetron deposition technique as well as ion-beam implantation (for samples with Vanadium). The presence of room temperature ferromagnetism in the samples has been initially checked by VSM and SQUID magnetometry measurements. The further magneto-optical (Transversal Kerr Effect) and transport (Hall Effect) measurements have been performed to obtain a more detailed picture of magnetism and concentration of carries. The special attention has been applied to verify an absence of any additional phases and magnetic impurities as metallic clusters insight the samples: in addition to a standard XRD analysis the element-specific XANES measurements at the Ti and 3d transition metal K- absorption edges have been done. The positron annihilation spectroscopy (PAS) has been used in order to investigate open volume defects on a very local scale and the first preliminary results will be presented.
The relationship of observed hysteresis loop in the sample magnetization, carrier concentration and characteristic features of magneto-optical spectra depending on film thicknesses, preparation route and structural defects is discussed. The difference in magnetic behaviour of TiO2:V and previously studied TiO2:Co is established.
This work is supported by the Initiative and Networking Fund of the German Helmholtz Association, Helmholtz-Russia Joint Research Group HRJRG-314 and RFBR #12-02-91321-SIG_а
References
1. Y. Matsumoto et al., Science 291, pp. 854 - 856 (2001).
2. H. Ohno et al., Appl. Phys. Lett. 69, 363 - 365 (1996).
3. H. Akai, Phys. Rev. Lett. 81, pp. 3002 - 3005 (1998).
4. S. Sonada et al., J. Cryst. Growth 237–239, 1358 (2002).
5. S.Q. Zhou et al., Appl. Phys. Lett. 93, pp. 232507 (2008).
6. A. F. Orlov et al., Phys. Solid State 53, pp. 482 - 484 (2011).
Keywords: diluted magnetic semiconductors
  • Lecture (Conference)
    ETOPIM (Electrical, Transport and Optical Properties of Inhomogeneous Media), 02.-07.09.2012, Marseille, Frankreich

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