Co-occurrence of Superparamagnetism and Anomalous Hall Effect in Highly Reduced Cobalt-Doped Rutile<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow><mml:mi>TiO</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn><mml:mo>−</mml:mo><mml:mi>δ</mml:mi></mml:mrow></mml:msub></mml:math>Films

Shinde, S. R.; Ogale, Satishchandra; Higgins, J. S.; Zheng, Haimei; Millis, Andrew J.; Kulkarni, V. N.; Ramesh, R.; Greene, R. L.; Venkatesan, T.

doi:10.1103/physrevlett.92.166601

Cited by 365 publications

(213 citation statements)

References 22 publications

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“…43 for Co-doped ZnO nanoparticles and from those in Ref. 53 for highly reduced Co-doped TiO 2−␦ thin films, where the FC and ZFC curves diverge substantially at low temperatures. From the first three graphs, Figs.…”

Section: Magnetic Measurementsmentioning

confidence: 99%

Ferromagnetism in Fe-doped ZnO nanocrystals: Experiment and theory

et al. 2007

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Fe-doped ZnO nanocrystals are successfully synthesized and structurally characterized by using x-ray diffraction and transmission electron microscopy. Magnetization measurements on the same system reveal a ferromagnetic to paramagnetic transition temperature above 450 K with a low-temperature transition from the ferromagnetic to the spin-glass state due to canting of the disordered surface spins in the nanoparticle system. Local magnetic probes like electron paramagnetic resonance and Mössbauer spectroscopy indicate the presence of Fe in both valence states Fe 2+ and Fe 3+ . We argue that the presence of Fe 3+ is due to possible hole doping in the system by cation ͑Zn͒ vacancies. In a subsequent ab initio electronic structure calculation, the effects of defects ͑e.g., O and Zn vacancies͒ on the nature and origin of ferromagnetism are investigated for the Fe-doped ZnO system. Electronic structure calculations suggest hole doping ͑Zn vacancy͒ to be more effective to stabilize ferromagnetism in Fe-doped ZnO and our results are consistent with the experimental signature of hole doping in ferromagnetic Fe-doped ZnO samples.

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Section: Magnetic Measurementsmentioning

confidence: 99%

Ferromagnetism in Fe-doped ZnO nanocrystals: Experiment and theory

et al. 2007

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“…There have also been a number of reports that ascribe the ferromagnetism to the Co segregation. 7,8,9 Strong evidence in support of intrinsic ferromagnetism has been given by the observations of anomalous Hall effect (AHE) and magnetic circular dichroism (MCD). 10,11,12,13,14 If the ferromagnetism were intrinsic, the charge carriers should be spin polarized due to the exchange interaction with the Co spins.…”

Section: Introductionmentioning

confidence: 99%

X-ray anomalous scattering of diluted magnetic oxide semiconductors: Possible evidence of lattice deformation for high temperature ferromagnetism

et al. 2007

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We have examined whether the Co ions crystallographically substitute on the Ti sites in rutile and anatase Ti1−xCoxO 2−δ thin films that exhibit room-temperature ferromagnetism. Intensities of the x-ray Bragg reflection from the films were measured around the K-absorption-edge of Co. If the Co ions randomly substitute on the Ti sites, the intensity should exhibit an anomaly due to the anomalous dispersion of the atomic scattering factor of Co. However, none of the anatase and rutile samples did exhibit an anomaly, unambiguously showing that the Co ions in Ti1−xCoxO 2−δ are not exactly located at the Ti sites of TiO2. The absence of the anomaly is probably caused by a significant deformation of the local structure around Co due to the oxygen vacancy. We have applied the same method to paramagnetic Zn1−xCoxO thin films and obtained direct evidence that the Co ions are indeed substituted on the Zn sites.

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“…It was reported that a secondary phase exists in the interface of TiO and its substrate for Co-doped TiO [13]. A crosssectional TEM sample was prepared for the x = 0.03 sample for such an investigation.…”

Section: Hrem Resultsmentioning

confidence: 99%