Ferromagnetism in chromium-doped reduced-rutile titanium dioxide thin films
25 May 2004-Journal of Applied Physics (American Institute of Physics)-Vol. 95, Iss: 11, pp 7381-7383
TL;DR: In this paper, a single phase and reduced-rutile TiO2 thin film was grown on R-plane sapphire substrates by pulsed-laser deposition.
Abstract: Cr-doped reduced-rutile TiO2 thin films were grown on R-plane sapphire substrates by pulsed-laser deposition. X-ray diffraction and transmission electron microscopy results indicate that the films are single phase and reduced-rutile type. Superconducting quantum interference device magnetometer measurements show the films are ferromagnetic up to 400 K. A large magnetic moment of 2.9 μB per Cr atom is found for 6% Cr-doped reduced films at room temperature, and the saturation magnetization of the films decreases with increasing Cr doping. The temperature dependence of the resistivity shows semiconducting behavior.
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TL;DR: In this paper, the authors 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.
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 TiO2 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.
489 citations
TL;DR: In this article, a review of the field of magnetically doped oxides and nitrides is presented from a materials science perspective, focusing on films prepared not only by conventional vacuum deposition methods, but also by spin coating colloidal nanoparticles in air.
228 citations
TL;DR: In this article, the feasibility of magnetic oxide semiconductors was examined from the viewpoint of feasibility to evaluate the ferromagnetism of Co-doped TiO2 and transition metal-dope ZnO.
Abstract: Magnetic oxide semiconductors, oxide semiconductors doped with transition metal elements, are one of the candidates for a high Curie temperature ferromagnetic semiconductor that is important to realize semiconductor spintronics at room temperature. We review in this paper recent progress of research on various magnetic oxide semiconductors. The magnetization, magneto-optical effect and magneto-transport such as the anomalous Hall effect are examined from the viewpoint of feasibility to evaluate the ferromagnetism. The ferromagnetism of Co-doped TiO2 and transition metal-doped ZnO is discussed.
190 citations
TL;DR: In this article, first-principles calculations for a number of C-doped structures in which C atoms substitute O atoms were performed and it was shown that each C has spin-polarized 2p states in the band gap generating a magnetic moment of 2.0μB.
Abstract: To see if ferromagnetism can occur in C-doped anatase TiO2, we performed first-principles calculations for a number of C-doped structures in which C atoms substitute O atoms. Our study shows that each C has spin-polarized 2p states in the band gap generating a magnetic moment of 2.0μB. The magnetic coupling between doped C atoms is substantial leading to either antiferromagnetism or ferromagnetism when the C⋯C distance lies between 3–4A. A strong ferromagnetic coupling occurs when the two C atoms form a slightly bent C–Ti–C unit by replacing two oxygen atoms at the opposite vertices of a TiO6 octahedron.
133 citations
TL;DR: In this article, dc-magnetization, electronic structural, and Raman investigations of Ti1−xMnxO2 (x = 0.00, 0.10, and 0.15) thin films deposited on fused-quartz substrate by a simple and cost effective spray pyrolysis technique have been reported.
Abstract: In this work dc-magnetization, electronic structural, and Raman investigations of Ti1−xMnxO2 (x = 0.00, 0.05, 0.10, and 0.15) thin films deposited on fused-quartz substrate by a simple and cost effective spray pyrolysis technique have been reported. X-ray diffraction revealed the formation of pure anatase TiO2 phase devoid of elemental Mn clusters in all the Mn incorporated TiO2 films. It is established by x-ray photoelectron spectroscopic (XPS) measurements that Ti ions substituted by Mn ions in both divalent and trivalent states in the TiO2 matrix. No peak corresponding to Mn+4 could be evidenced by XPS. The Raman study has further established the formation of TiO2 in anatase structure in both pure TiO2 and Mn-doped TiO2 films. The Ti1−xMnxO2 films with x ≥ 0.05 exhibit ferromagnetic ordering at room temperature which arises most likely due to formation of bound magnetic polarons.
98 citations
References
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TL;DR: Zener's model of ferromagnetism, originally proposed for transition metals in 1950, can explain T(C) of Ga(1-)(x)Mn(x)As and that of its II-VI counterpart Zn(1)-Mn (x)Te and is used to predict materials with T (C) exceeding room temperature, an important step toward semiconductor electronics that use both charge and spin.
Abstract: Ferromagnetism in manganese compound semiconductors not only opens prospects for tailoring magnetic and spin-related phenomena in semiconductors with a precision specific to III-V compounds but also addresses a question about the origin of the magnetic interactions that lead to a Curie temperature (T(C)) as high as 110 K for a manganese concentration of just 5%. Zener's model of ferromagnetism, originally proposed for transition metals in 1950, can explain T(C) of Ga(1-)(x)Mn(x)As and that of its II-VI counterpart Zn(1-)(x)Mn(x)Te and is used to predict materials with T(C) exceeding room temperature, an important step toward semiconductor electronics that use both charge and spin.
7,062 citations
TL;DR: The magnetic coupling in all semiconductor ferromagnetic/nonmagnetic layered structures, together with the possibility of spin filtering in RTDs, shows the potential of the present material system for exploring new physics and for developing new functionality toward future electronics.
Abstract: REVIEW Semiconductor devices generally take advantage of the charge of electrons, whereas magnetic materials are used for recording information involving electron spin. To make use of both charge and spin of electrons in semiconductors, a high concentration of magnetic elements can be introduced in nonmagnetic III-V semiconductors currently in use for devices. Low solubility of magnetic elements was overcome by low-temperature nonequilibrium molecular beam epitaxial growth, and ferromagnetic (Ga,Mn)As was realized. Magnetotransport measurements revealed that the magnetic transition temperature can be as high as 110 kelvin. The origin of the ferromagnetic interaction is discussed. Multilayer heterostructures including resonant tunneling diodes (RTDs) have also successfully been fabricated. The magnetic coupling between two ferromagnetic (Ga,Mn)As films separated by a nonmagnetic layer indicated the critical role of the holes in the magnetic coupling. The magnetic coupling in all semiconductor ferromagnetic/nonmagnetic layered structures, together with the possibility of spin filtering in RTDs, shows the potential of the present material system for exploring new physics and for developing new functionality toward future electronics.
4,339 citations
TL;DR: The occurrence of room temperature ferromagnetism is demonstrated in pulsed laser deposited thin films of Sn(1-x)Co(x)O(2-delta) (x<0.3) and a giant magnetic moment of 7.5+/-0.5 micro(B)/Co, not yet reported in any diluted magnetic semiconductor system.
Abstract: The occurrence of room temperature ferromagnetism is demonstrated in pulsed laser deposited thin films of Sn(1-x)Co(x)O(2-delta) (x<0.3). Interestingly, films of Sn(0.95)Co(0.05)O(2-delta) grown on R-plane sapphire not only exhibit ferromagnetism with a Curie temperature close to 650 K, but also a giant magnetic moment of 7.5+/-0.5 micro(B)/Co, not yet reported in any diluted magnetic semiconductor system. The films are semiconducting and optically highly transparent.
803 citations
TL;DR: In this paper, the spin-orbit interaction of a room-temperature-diluted magnetic semiconductor was investigated, and the half-metallic ground state in the local-spin-density approximation (LSDA) was obtained for Co-doped anatase.
Abstract: We have investigated electronic structures of a room-temperature-diluted magnetic semiconductor: Co-doped anatase ${\mathrm{TiO}}_{2}.$ We have obtained the half-metallic ground state in the local-spin-density approximation (LSDA) and the insulating ground state in the $\mathrm{LSDA}+U+\mathrm{SO}$ incorporating the spin-orbit interaction. In the stoichiometric case, the low spin state of Co is realized with the substantially large orbital moment. However, in the presence of oxygen vacancies near Co, the spin state of Co becomes intermediate. The ferromagnetisms in the metallic and insulating phases are accounted for by the double-exchange-like and the superexchange mechanisms, respectively. Further, the magnetic ground states are obtained for Mn- and Fe-doped ${\mathrm{TiO}}_{2},$ while the paramagnetic ground state is obtained for Ni-doped ${\mathrm{TiO}}_{2}.$
165 citations
TL;DR: In this paper, room-temperature ferromagnetism was observed in reduced rutile TiO2−δ by Fe doping, and the epitaxial films were carefully examined by x-ray diffraction, transmission electron microscopy, and magnetic and transport measurements.
Abstract: Room-temperature ferromagnetism is observed in reduced rutile TiO2−δ by Fe doping. The epitaxial films grown by pulsed-laser deposition are carefully examined by x-ray diffraction, transmission electron microscopy, and magnetic and transport measurements. The films exhibit the extraordinary Hall-effect and thin-film magnetic shape anisotropy. The magnetic moments and anticipated Curie temperatures of the films rule out Fe particles, iron oxides, and Ti–Fe oxides as possible sources for the observed magnetic signals. The carriers of the Fe-doped reduced rutile are p-type, with a carrier density of 1×1022/cm3. This room-temperature dilute magnetic semiconductor should find potential applications in spintronics.
139 citations