Transition metal-doped TiO₂and ZnO—present status of the field

Abstract

There has been considerable recent interest in the design of diluted magnetic semiconductors, with a particular focus on the exploration of different semiconductor hosts. Among these, the oxide-based diluted magnetic semiconductors are attracting increasing attention, following reports of room temperature ferromagnetism in anatase TiO 2 and wurtzite ZnO doped with a range of transition metal ions. In this review we summarize the current status of oxide-based diluted magnetic semiconductors, and discuss the influence of growth method, substrate choice, and temperature on the microstructure and subsequent magnetic properties of thin films. We outline the experimental conditions that promote large magnetization and high ferromagnetic Curie temperature. Finally, we review the proposed mechanisms for the experimentally observed ferromagnetism and compare the predictions to the range of available data.

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

“…These exhibit large MCD without an appearance of ferromagnetism, although several studies reported high-T C ferromagnetism in the same compound. 5,6 X-ray diffraction experiments were performed using four-circle diffractometers installed at beamlines 1A, 4C, and 16A2 of the Photon Factory in KEK, Japan. The incident beam was monochromatized by a Si-111 double crystals and focused by a bent cylindrical mirror.…”

“…1,2 Since the discovery of room temperature ferromagnetism in Codoped anatase and rutile TiO 2 thin film, 3,4 there have been a number of reports on high-T C ferromagnetism observed in various kinds of DMS, particularly in oxides. 5,6 Co-doped TiO 2 is the material that has been studied most intensively. However, the origin of the ferromagnetism has not yet been elucidated.…”

“…16,17,18,19 In these spectroscopic measurements, the spectral line shapes differ from that of Co metal. They state that the local structure of the Co site is close to those of Co oxides such as CoTiO 3 , in which the Co ion is surrounded by six oxygen atoms, forming a CoO 6 cluster, and that the valence state of Co is divalent. Cui et al performed electron beam diffraction and composition analysis for anatase TiO 2 in a selected area without Co segregation and confirmed both the diffraction peaks of TiO 2 and the existence of Co. 20 These results seem to support that the Co ions randomly substitute on the Ti sites.…”

Large-Scale Synthesis of Transition-Metal-Doped TiO2 Nanowires with Controllable Overpotential

“…Historically, a variety of these transition-metals have been explored as dopants in modifying the electronic structure of TiO 2 to improve its visiblelight photocatalytic activity. [25][26][27][28] Because of the interaction between t 2g state of TM-dopants and Ti atoms, transitionmetal doping could considerably create an additionally oc- Figure S5) exhibit a variety of colors, departing from the white color of the undoped product. For instance, Rh-doped samples show a deep brown color resulted from the strong absorption in visible region (Figure 2).…”

Optical properties of oxide magnetic ZnO, Zn0.95Mn0.05O and Cu2O nanopowders

“…

Recently, it was found that the ZnO, TiO 2 , Cu 2 O and SnO 2 oxide semiconductors, doped by 3Delements can be ferromagnetic with the Curie temperature significantly above room temperature when the magnetic ions concentration is significantly lower than the percollation threshold [1][2][3]. As a rule these compounds are prepared in the form of nanocrystals by means of substantially nonequilibrium technique with large number of defects (for example, the vacancies in anion (oxygen) or cation sublattice as well as surface defects).

…”