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The effect of Al doping on the magnetic properties of Zn(Cu)O based diluted magnetic semiconducting thin films is examined. The results have shown that carrier induced exchange is not directly responsible for the magnetic properties of these materials.

The implantation of ZnO with dilute, radioactive [super 57][Mn.sup.+] ions has shown that Fe atoms are in a magnetically ordered atomic surrounding with ordering temperatures >>600 K. The results have challenged the concepts regarding the modeling of magnetic ordering in 3d-metal doped oxides and have shown this role of vacancies in the magnetism to be a general

The study result from comparable magnetotransport measurement on Co-doped ZnO and Mn-doped ZnO films is reported. The saturated anomalous Hall resistivity observed for Co-doped ZnO was found to increase with decreasing electron concentration while Mn-doped ZnO showed no anomalous Hall effect.

The epitaxial growth and properties of Co and Cu codoped ZnO thin films deposited onto sapphire c-plane single crystals by using pulsed-laser deposition are studied. The presence of high oxygen vacancies in the films have allowed possible defect mediated mechanisms for mediating exchange coupling of the dopant ions resulting in room temperature ferromagnetism.

A study is conducted of the room temperature effective permeability tensor components of fine-grained composites composed of polycrystalline magnetic ZnO, Co, gamma- [Fe.sub.2][O.sub.3] and Ni particles and the observations on the frequency and composition dependences at various magnetic fields are reported. It is found that magnetically structured granular systems comprised of magnetic grains embedded in a nonmagnetic matrix is likely to have quite different behaviors depending on their constituents.

Study is presented to show that there is a mechanism promoting room temperature ferromagnetism (RT FM) in [Co.sub.3][O.sub.4]-ZnO bulk samples different than carrier mediation or segregated cobalt metallic clusters. This mechanism is associated with a partial reaction of ZnO and [Co.sub.3][O.sub.4] grains and appears when the starting phases ZnO and [Co.sub.3][O.sub.4] are present in the sample.

(Mn, Co)-codoped ZnO films are synthesized on c-sapphire (001) by a radio-frequency magnetron sputtering system in which two targets are sputtered together. X-ray diffraction measurements indicate that the films are highly c-axis oriented.

The full potential linearized augmented plane wave method is used to explore the magnetization and magnetic ordering of Co doped ZnO. Nonuniform distribution and antiferromagnetic ordering is preferred by energetically Co and both Zn and O display measurable x-ray magnetic circular dichroism spectra.

The magnetic and transport properties of Mn-doped ZnO thin films codoped with Sn are examined. Superconducting quantum interface device magnetometry measurements indicate that the films are ferromagnetic with an inverse correlation between magnetization and electron density as controlled by Sn doping.

In this article, by studying structural and magnetic properties of transition metal substituted polycrystalline ZnO samples, it is found that no bulk ferromagnetism exists for single-phase materials, contrary to the existing theories.

A promising epitaxial growth technique, namely helicon-wave-excited plasma sputtering epitaxy (HWPSE), is proposed for the growth of ZnO epilayers. The ZnO epilayer exhibited a dominant near-band-edge photoluminescence (PL) peak at 300 K.

Copper-doped ZnO (ZnO:Cu) films are prepared on silicon substrates by filtered cathodic vacuum arc technique at room temperature using a Zn target containing 5 at. % of Cu. X-ray diffraction, x-ray photoelectron spectroscopy, and transmission electron microscopy reveals that no ferromagnetic-related secondary could be detected in ZnO:Cu.

Four kinds of Li and Co codoped ZnO (LCZO) thin films are prepared by a sol-gel process technique. X-ray diffraction results reveal that the LCZO thin films possess single ZnO wurtzite structure and c-axis preferred orientation, and Li and Co ions substitute for the Zn sites without changing the wurtzite structure.

Structural and magnetic properties are studied for polyscrystalline Zn(sub 1-x)Mn(sub x)O (x=0.02,0.03,0.05). The results state that single phase samples show paramagnetic Curie-Weiss behavior.

The comparative analysis of magnetization, resistivity and magnetoresistance measurements of ZnO:Co structures is done. The structures are diluted magnetic semiconductor (DMS) superlattices at small thickness of Co layers in the multilayer samples.

The Perdew-Burke-Ernzerhof form of generalized gradient approximation is used for analyzing the electronic and magnetic properties of (Mn,N)-codoped ZnO within the framework of the density functional theory. The analysis of geometrical configurations for (Mn,N)-codoped ZnO has shown that the ground state is changed from no-metallic AFM to half-metallic ferromagnetic, which is because of the strong hybridization between N sp and Mn 3d states.

The growth, as well as the structural and magnetic properties exhibited by the epitaxial [Fe.sub.3][O.sub.4/ZnO and ZnO/[Fe.sub.3][O.sub.4] bilayers grown on c-[Al.sub.2][O.sub.3] substrate are discussed. The [Fe.sub.3][O.sub.4/ZnO bilayer is shown to be much more stable, as compared to the other bilayers.

The occurrence of high temperature ferromagnetism (FM) in ZnO nanoparticles (NPs) doped with Co-atoms is described. The studies have showed that high temperature FM is mediated by defects in the strained NPs and ZnO NPs of lower initial size has shown enhanced FM, which is attributed to size dependent doping effect.

The electronic and magnetic properties of pure and Mn-doped armchair and zigzag ZnO nanotubes are analyzed by using density functional theory with the generalized gradient approximation. The studies have shown that large magnetic moments have appeared in Mn-doped ZnO nanotubes, which are due to the hybridization between the O 2p and Mn 3d states.

Epitaxial films of ZnO doped with magnetic ion Fe and Al has shown room temperature ferromagnetic ordering. The magnitude of junction magnetoresistance has depended on the magnitude of the magnetic moment of the dilute magnetic semiconductor films and these properties are explained by stdandard spin injection theory.

Dense nanograined pure and Mn-doped [Zn.sub.1-x][Mn.sub.x]O polycrystals are prepared by the wet chemistry method from butanoate precursors. The shape of the dependence of saturation magnetization on Mn concentration is different for the Mn-doped nanograined ZnO prepared by different methods and it is controlled by the topology of grain boundary network in the ZnO polycrystals.

The structural, chemical, electrical, optical and magnetic properties of undoped ZnO thin films grown under different conditions as well as the films that are annealed in various environments are analyzed. The studies have shown that the ferromagnetic order in ZnO matrix is defect-mediated.

The structural and magnetic properties of pulsed laser deposited zinc oxide thin films are examined. The ferromagnetism has occurred from intrinsic defects in the ZnO that can be varied by manipulation of the lattice parameter.

Nanocrystalline Gd-doped ZnO thin films are prepared by using versatile pulsed spray pyrolysis method and have displayed room temperature ferromagnetism. Hysteresis measurements have shown that the Gd-doped ZnO films are magnetically anisotropic and have displayed intrinsic ferromagnetic behavior at room temperature.

Multiferroic BiFe[O.sub.3] thin film is grown on the ZnO-buffered Pt/Ti[O.sub.2]/Si[O.sub.2](100) substrate by off-axis radio frequency magnetron sputtering, where the ZnO buffer layer has produced a strong (110) texture for the BiFe[O.sub.3] thin film. The ZnO as a buffer layer for BiFe[O.sub.3] has changed the dielectric relaxation and conduction mechanisms.

The role of oxygen atoms in the growth of magnetron sputter-deposited ZnO films is analyzed by alternating the deposition of a several-nanometer-thick ZnO layer and the [O.sub.2]/Ar mixture plasma exposure, that is, layer-by-layer technique. The diffusion and effusion of oxygen atoms at the growing surface have played a role of thermal annealing, promoted the film crystallization as well as the creation and the annihilation of oxygen and zinc related defects.

A combination of the x-ray absorption structure and other techniques is employed to explain the structural, as well as the magnetic properties of the different Co:ZnO magnetic films. The presence of O vacancy is shown to play an extremely significant role in the ferromagnetic interactions of the films.

Several studies are conducted to explain the formation, as well as the different photoluminescence properties of the emissions taking place in the [Zn.sub.1-x][Co.sub.x]O layers. The suppression of excitonic emissions is shown to be extremely beneficial in the enhancement of the intraemissions taking place in these layers.

The anisotropic structural properties of periodically polarity-inverted (PPI) ZnO structures grown on patterned templates are studied. The structures at transition region have shown relationship with the anisotropic crystal quality.

Simultaneous room temperature ferroelectricity and magnetic properties are observed in (Co, Li) coimplanted ZnO films. The ionic radius difference between the dopants and host cations is used for interpreting the ferroelectricity and the magnetism is described by bound magnetic polarons mediated by electrons and defects.

The electronic structure of Cu-doped ZnO thin films, prepared with a nominal composition of [Zn.sub.1-x][Cu.sub.x]O by using spray pyrolysis method, is examined by using near-edge x-ray absorption fine structure (NEXAFS) experiments at the O K- and the Cu[L.sub.3.2]-edges and resonant inelastic x-ray scattering (RIXS) measurements at Cu [L.sub.3.2] edge. The results have shown that Cu is in mixed valence state of [Cu.sup.2+/3+][Cu.sup.1+], substituting at the Zn site and [Cu.sup.2+/3+] ions are magnetically polarized.

Several experimental techniques are employed to explain the angular dependence of the ferromagnetic resonance observed in the different metal nanocrystals in Fe, as well as Ni implanted ZnO. The resonance is shown to be perpendicular to the sample surface in case of the Fe nanocrystals.

Several studies are conducted to explain the synthesis and the dielectric and magnetic properties of the various different ferroelectric/ferromagnetic composites. An increase in the content of [B.sub.2][O.sub.3]-[Bi.sub.2][O.sub.3]-Si[O.sub.2]-ZnO glass in the composites is shown to lead to significant enhancement of the properties of the compounds.

The s-d model and Green's function method are used for studying the impact of transition metal doping effects on different properties such as magnetization M, Curie temperature [T.sub.c], and coercive field [H.sub.c] of ZnO nanoparticles. The studies have shown that room temperature ferromagnetism is an intrinsic property and it is due to doping effects in ZnO nanoparticles.

Several studies are conducted to explain the electronic structure, as well as the surface magnetism observed in the various ZnO/[Co.sub.3][O.sub.4] mixtures. The various electrostatic interactions taking place between the oxides of the mixtures are also analyzed.

The theoretical studies of the electronic structures and magnetic properties of (Mn,C)-codoped ZnO system based on the first-principles calculations within a GGA+[U.sub.p,d] approach is presented. The spin-polarized states induced by C which could mediate long-ranged ferromagnetic exchange interactions beyond the nearest-neighboring case indicated (Mn,C)-codoped ZnO to be a ferromagnetic semiconductor with long-ranged ferromagnetism and high curie temperature.

A detailed spectroscopic and x-ray magnetic circular dichroism (XMCD) are conducted to study the electronic structure of Fe-doped ZnO nanoparticles reported to exhibit ferromagnetism at room temperature. The room temperature ferromagnetism in the Fe-doped ZnO nanoparticles primarily originated from the antiferromagnetic coupling between unequal amounts of [Fe.sup.3+] ions occupying two sets of nonequivalent positions in the region of the XMCD.

First-principles total-energy calculations are used for examining the effects of O vacancy ([V.sub.o]) on the electronic and magnetic properties of Co-doped ZnO. The effects of O vacancy at metastable sites have induced the ferromagnetic (FM) coupling between nearest-neighbor (NN) Co ions and the atoms around the FM-coupled NN Co ions are spin-polarized, which has led to the long-ranged FM coupling between Co ions.

Intrinsic ferromagnetism at room temperature is observed in ZnO/sapphire films by implantation of 200 keV [Ni.sup.2+] ions. Defectlike oxygen vacancies in the films are analyzed by x-ray photoelectron spectroscopy and ferromagnetism of the films is described based on the bound magnetic polaron model.

The article presents a new approach, which can be used for the synthesis of alkali doped ZnO nanorods, exhibiting a high temperature carrier controlled ferromagnetism. The ferromagnetic exchange interaction is shown to lead to high Curie temperature in the system.

First-principles density functional calculations are used for studying the electronic structure and magnetic properties of Mn-doped ZnO, wurtzite crystal structure, with various defects. The studies that shown that higher values of Curie temperature are obtained for high concentration of vacancy defects sites in (Zn,Mn)O and for small concentration of vacancy defects sites in (Zn,Mn)(O,N).

First-principles density functional calculations with generalized gradient approximation ZnO:Co (1010) thin films are shown not to display a ferromagnetic behavior in the absence of any additional carrier doping. The results have shown that N codoping has changed the ground state from antiferromagnetic to ferromagnetic while maximum ferromagnetic state stability has occurred for N concentration.

The radio sputtering magnetron sputtering method is used for growing As-doped ZnO films. The results of x-ray photoelectron spectroscopy, photoluminescence and positron annihilation spectroscopy have presented a comprehensive picture of the As-related shallow acceptor formation.

The defects in ZnO are discussed emphasizing on the physical properties of point defects in bulk crystals. The properties of group-I (Cu, Li and Na) and group-V (N, P, As, and Sb) acceptors and their complexes with H are discussed.

Magnetron sputtering is used for obtaining ZnO/Cu/ZnO multilayer structures with very high conductivity. Pole figure results have shown that the copper midlayer has acted as a hindrance to (002) ZnO texturing rather than as a seed layer and they have confirmed the mechanism of conduction.

The electronic structure and magnetic coupling properties of rare-earth metals (Gd, Nd) doped ZnO are examined by using first-principles methods. For ZnO:Nd system, the ferromagnetism between Nd ions is enhanced by appropriate holes doping into the sample and the room-temperature ferromagnetism is achieved in the n-conducting ZnO:Nd sample.

The vacancy defect induced magnetism in wurtize ZnO is explored and it is shown that the Zn vacancy defect has brought a spin polarized state in the nearest neighbor oxygen atoms, whereas the oxygen vacancy defect has no impact on the magnetism. The results have shown that the ferromagnetic exchange interaction among oxygen atoms is mediated by Zn 3d state.

A sputtered [Zn.sub.0.95][Co.sub.0.05]O layer is chemically studied at the atomic scale in order to give an accurate image of the distribution of Co atoms in the ZnO matrix. The magnetic properties have shown that the as-deposited [Zn.sub.0.95][Co.sub.0.05]O is ferromagnetic at room temperature and hence the ferromagnetic properties are not attributed to the secondary phase or to metallic Co precipitates within the layer.

The room temperature ferromagnetism (RTF) observed for the pure ZnO nanoparticles prepared by coprecipitation method is described. The results confirmed the significant role of the oxygen vacancies for introducing ferromagnetism for the ZnO nanoparticles.

The pulsed-laser deposition-based preparation and the determination of growth-dependent properties of [Zn.sub.0.97][Cu.sub.0.03]O films grown on c-cut sapphire substrates under various conditions is reported. The results showed that the itinerant electrons introduced by oxygen-deficient or Zn-rich atmospheres might contribute significantly to room temperature ferromagnetism observed in the ZnCuO dilute magnetic semiconductor.