Oxide-diluted Magnetic Semiconductor Research Articles

Regulated the ferromagnetism of In[formula omitted]O[formula omitted] quantum dots by non-stoichiometry compositions

Due to different versions of ferromagnetic origin, the magnetic properties of oxide diluted magnetic semiconductor (ODMS) cannot be accurately determined. We have systematically investigate the magnetic properties and electronic structure of In2O3 quantum dots (Qds) with non-stoichiometry ratio by first-principle method with band-structure calculations. For the sake of contrastive analysis, some models are proposed to passivate the surface dangling bonds by pseudo-hydrogen atoms. We find that: (i), dangling bonds of oxygen atoms on the surface of Qds can induce 6 μB magnetic moments due to imbalanced chemical proportion. Spin polarization energy of the structure is as low as −763 eV. (ii), internal cation vacancy can induce magnetic moment, while internal anionic vacancy or surface hanging bond passivated by pseudo-hydrogen atoms cannot produce magnetic moment; and (iii), it has broken the chemical balance ratio of doping cobalt atoms where the magnetic moment mainly local area in the cobalt atoms and a little are distributed on some special O atoms which binding with the Co atoms. All three kinds of above results indicate that the non-stoichiometry compositions play an special roles to effect the magnetic properties and electronic structure in In2O3 Qds.

Mesoporous Oxide-Diluted Magnetic Semiconductors Prepared by Co Implantation in Nanocast 3D-Ordered In2O3–y Materials

Mesoporous In2O3–y materials have been implanted using Co ions to induce a moderate ferromagnetic response at room temperature, forming a “mesoporous oxide-diluted magnetic semiconductor” (MODMS). X-ray photoemission spectroscopy (XPS) reveals that implantation results in up to 1 at. % Co (for 6 × 1015 ions/cm2 at 40 keV) and 15 at. % Co (for 1 × 1017 ions/cm2 at 60 keV). This is in both cases accompanied by a pronounced increase in the amount of oxygen vacancies with respect to the pristine, nonimplanted, In2O3–y. Further increase in the ion fluence (up to 2 × 1017 ions/cm2 at 60 keV) results in the collapse of the mesoporous structure, i.e., loss of the 3D-ordered porous configuration. XPS also reveals that virtually no metallic Co is formed at 40 keV, while a mixture of Co2+ and Co0 states is detected after implantation at 60 keV. Most of the Co2+ is incorporated in the bixbyite structure of the In2O3–y matrix. These results are consistent with previous models suggesting that the origin of the obtained...

Sr and Mn co-doped LaCuSO: A wide band gap oxide diluted magnetic semiconductor with TC around 200 K

Here we report the synthesis of a bulk oxide diluted magnetic semiconductor (DMS) system La1−xSrxCu0.925Mn0.075SO (x = 0, 0.025, 0.05, 0.075, and 0.1). As a wide band gap p-type oxide semiconductor, LaCuSO satisfies all the conditions forecasted theoretically to be a room temperature DMS. The Curie temperature (TC) is around 200 K as x ≥ 0.05, which is among the highest TC record of known bulk DMS materials up to now. The system provides a rare example of oxide DMS system with p-type conduction, which is important for formation of high temperature spintronic devices.

An Oxide-Diluted Magnetic Semiconductor: Co-Doped ZnO

The discovery of ferromagnetism (FM) in wide band-gap semiconductors doped with transition metals (TM), known as diluted magnetic semiconductors (DMSs), has attracted much interest. These materials are applicable to spin-based optoelectronic devices working at room temperature (RT). Among DMSs, the system of Co-doped ZnO is considered as the most promising candidate, which was expected to robust magnetism. This paper focuses primarily on the recent progress in the experimental studies of ZnO:Co DMSs. The magnetic properties and possible mechanism of ZnO:Co DMSs prepared by different methods are summarized and reviewed.

Room-temperature ferromagnetism of diamagnetically-doped ZnO aligned nanorods fabricated by vapor reaction

Large-scale monocrystalline oxide-diluted magnetic semiconductor (ODMS) Zn1−xBixO nanorods arrays (NAs) were prepared within a large doping concentration range from 5% to 20% by a simple chemical vapor deposition. X-ray diffraction and high-resolution transmission electron microscopy reveal the monotonous expansion of the lattice constants with increasing Bi content, due to the effective Bi doping. In particular, room-temperature ferromagnetic (RTFM) behavior with Curie temperature over 363.7 K has been observed based on Bi-doped ZnO nanoarrays, whereas undoped ZnO NAs disappear. The RTFM origin is suggested, in which vacancies can be controlled to tune the FM. The as-formed RTFM NAs would have potential applications in many areas of advanced nanotechnology, such as new spintronic devices and magneto-optic components.

Local structure distortion and spin Hamiltonian parameters of oxide-diluted magnetic semiconductor Mn-doped ZnO

The local structure distortion, the spin Hamiltonian (SH) parameters, and the electric fine structure of the ground state for Mn2+ (3d5) ion in ZnO crystals are systematically investigated, where spin–spin (SS), spin–other-orbit (SOO) and orbit–orbit (OO) magnetic interactions, besides the well-known spin-orbit (SO) coupling, are taken into account for the first time, by using the complete diagonalization method. The theoretical results of the second-order zero-field splitting (ZFS) parameter D, the fourth-order ZFS parameter (a-F), the Zeeman g-factors: g// and g⊥, and the energy differences of the ground state: δ1 and δ2 for Mn2+ in Mn2+: ZnO are in good agreement with experimental measurements when the three O2– ions below the Mn2+ ion rotate by 1.085° away from the [111]-axis. Hence, the local structure distortion effect plays an important role in explaining the spectroscopic properties of Mn2+ ions in Mn2+: ZnO crystals. It is found for Mn2+ ions in Mn2+: ZnO crystals that although the SO mechanism is the most important one, the contributions to the SH parameters, made by other four mechanisms, i.e. SS, SOO, OO, and SO∼SS∼SOO∼OO mechanisms, are significant and should not be omitted, especially for calculating ZFS parameter D.

Pulsed laser ablation of preferentially orientated ZnO:Co diluted magnetic semiconducting thin films on Si substrates

ZnO:Co thin films with room-temperature ferromagnetism have been synthesized on (001) Si substrates by pulsed laser deposition using a Zn0.95Co0.05O ceramic target. Single-phase wurtzite thin films with (002) preferential orientation were grown at 450°C in vacuum. There is no indication of Co nanocluster formation. However, copious edge dislocations appear to have formed during the film growth. A saturation magnetization of 1.04μB∕Co and a coercivity of 25Oe were obtained at room temperature. In addition to O vacancies, the Zn interstitial induced by edge dislocations may also contribute to the ferromagnetic properties in this oxide-diluted magnetic semiconductor.

Rutile-type oxide-diluted magnetic semiconductor: Mn-doped SnO2

Epitaxial films of an oxide-diluted magnetic semiconductor with rutile structure, Mn-doped SnO2, have been fabricated by pulsed-laser deposition. As the Mn content increases, systematic changes in lattice constants and in-gap absorption are observed. Magnetization measurements show almost paramagnetic behavior. The injection of n-type carrier over 1020 cm−3 is achieved by Sb doping. A Sn0.95Mn0.05O2:Sb film shows giant positive magnetoresistance as large as 60% at 5 K.

Magnetic properties of Mn-doped ZnO

We report on the magnetic properties of an oxide-diluted magnetic semiconductor (DMS), Zn0.64Mn0.36O. The temperature dependence of the magnetization shows a spin-glass behavior with the large magnitude of the Curie–Weiss temperature, corresponding to a stronger antiferromagnetic exchange coupling than other II–VI DMSs. The small effective Mn moment (x̄∼0.02) under high field also represents a strong antiferromagnetic exchange coupling in this compound.

An oxide-diluted magnetic semiconductor: Mn-doped ZnO

Epitaxial thin films of an oxide-diluted magnetic semiconductor, Mn-doped ZnO, were fabricated by pulsed-laser deposition technique. Solubility of Mn into ZnO exceeds thermal equilibrium limit as a result of nonequilibrium film growth process. As Mn content is increased, the lattice constants of both a and c axes of wurtzite Zn1−xMnxO films (x<0.35) increase and the band gap expands although considerable in-gap absorption develops. Itinerant electrons over 1019 cm−3 can be doped into the Zn1−xMnxO films by Al doping, in contrast to low carrier density in the other II–VI diluted magnetic semiconductors. The temperature dependence of the resistivity is almost metallic and considerable magnetoresistance is observed at low temperatures.