Exhibit Room Temperature Ferromagnetism Research Articles

Synthesis and characterization of niobium doped titanium oxide for spintronics applications

Spintronics is a promising field that involves vast applications exploiting both the intrinsic spin of the electron and its charge. Transition metal doped oxide based dilute magnetic semiconductors (DMS) are suitable for these purposes. This work reports undoped and niobium-doped titanium oxide (XNb=0.00, 0.5% and 1 wt%) nanoparticles, synthesized by a modified hydrothermal method. The structural properties were studied using X-ray diffraction, (XRD), which has depicted that the dopant niobium is well incorporated in the anatase titanium oxide lattices. The surface morphology of the freshly synthesized nanoparticles indicates the formation of spherical nanoparticles without any irregular structures, with good agreement of the particle sizes to the XRD results. Fourier-transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV) studies confirm the purity and the expected phases of the Nb doped TiO2. Vibrating sample magnetometer (VSM) studies show evidence of enhanced room temperature ferromagnetism in Nb doped TiO2. The optical properties of freshly synthesized Nb doped TiO2 reveal a band gap energy of around 3.12 eV. These results authenticate a good reason for considering a dilute magnetic semiconductor exhibiting room temperature ferromagnetism for spintronics applications.

Impact of Cr doping on the structure, optical and magnetic properties of nanocrystalline ZnO particles

The doping of Cr ions on the structure, optical and magnetic properties of ZnO have been investigated. Zn1−xCrxO (0 ≤ x ≤ 0.05) samples were prepared by the solution combustion method. Rietveld refined x-ray diffraction results reveal that all the samples are in a hexagonal structure. Transmission electron microscopy (TEM) revealed that the particle size was 48.2 ±2.1 nm, 29.4 ± 2.2 nm and 25.3 ± 2.1 nm for the Zn1−xCrxO with x = 0, 0.03 and 0.05, respectively. The band-gap decreases slightly from 3.308 ± 0.003 eV to 3.291 ± 0.003 eV with increase of Cr content from x = 0 to 0.05, respectively. The field-dependent magnetization M(μοH) measurements of ZnO and Cr-doped ZnO exhibit room temperature ferromagnetism (RTFM). Photoluminescence and electron paramagnetic resonance exhibits negatively charged zinc vacancies (VZn−) and singly ionized oxygen vacancies (Vo+) in ZnO and these defects are responsible for RTFM. And the VZn− accountable for RTFM in Cr-doped ZnO. EPR results confirmed that Cr3+ ions replaces the Zn2+ sites in the hexagonal ZnO. The observed long-range ferromagnetism ordering is explained based on the bound magnetic polaron (BMP) mechanism. This work elucidates the origin of RTFM in synthesized ZnO and Cr-doped ZnO.

Magnetic supercapacitors: Charge storage mechanisms, magnetocapacitance, and magnetoelectric phenomena

Pseudocapacitive (PC) materials are under investigation for energy storage in supercapacitors, which exhibit exceptionally high capacitance, good cyclic stability, and high power density. The ability to combine high electrical capacitance with advanced ferrimagnetic or ferromagnetic properties in a single material at room temperature opens an avenue for the development of advanced magnetically ordered pseudocapacitive (MOPC) materials. This review covers materials science aspects, charge storage mechanisms, magnetocapacitance, and magnetoelectric (ME) phenomena in MOPC materials. Recent studies demonstrate high PC properties of advanced ferrimagnetic materials, such as spinel ferrites and hexagonal ferrites. Of particular importance is the discovery of PC properties of perovskite-type manganites, which exhibit room temperature ferromagnetism and giant negative magnetoresistance. The coupling of high capacitance and magnetization in MOPC provides a platform for strong ME interactions. Various strategies are used for manipulation of electrical capacitance/magnetization of MOPC by a magnetic field/electrode potential. Magnetocapacitance studies show significant increase in capacitance of MOPC under the influence of a magnetic field. Moreover, the application of a magnetic field results in enhanced energy density and power density, reduction of resistance, and improvement of cyclic stability. Such findings offer a potential of a breakthrough in the development of advanced supercapacitors. High magnetocapacitance and ME phenomena are linked to the influence of magnetic fields on electrolyte diffusion, structure of electrical double layer, charge transfer resistance, and variation of conductivity and magnetization of MOPC materials, which facilitate charge/discharge behavior. Various applications of ME effect in MOPC are discussed. Moreover, advantages of magnetocapacitive MOPC are described for applications in electronic and spintronic devices, supercapacitors, and devices for magnetically enhanced capacitive deionization of water.

Rare Earth Doped ZnO Nanoparticles as Spintronics and Photo Catalyst for Degradation of Pollutants.

Antibiotic water contamination is a growing environmental problem in the present day. As a result, water treatment is required for its reduction and elimination. Due to their important role in resolving this issue, photocatalysts have drawn a great deal of interest over the past few decades. When non-biodegradable organic matter is present in polluted water, the photo catalytic process, which is both environmentally friendly and an improved oxidation method, can be an effective means of remediation. In this regard, we report the successful synthesis of pure phased rare earth doped ZnO nanoparticles for tetracycline degradation. The prepared catalysts were systematically characterized for structural, optical, and magnetic properties. The optical band gap was tailored by rare earth doping, with redshift for Sm and Dy doped nanoparticles and blueshift for Nd doped ZnO nanoparticles. The analysis of photoluminescence spectra revealed information about the defect chemistry of all synthesised nanoparticles. Magnetic studies revealed that all synthesized diluted magnetic semiconductors exhibit room temperature ferromagnetism and can be employed for spintronic applications. Moreover, Dy doped ZnO nanoparticles were found to exhibit a maximum degradation efficiency of 74.19% for tetracycline (TCN) removal. The synthesized catalysts were also employed for the degradation of Malachite green (MG), and Crystal violet (CV) dyes. The maximum degradation efficiency achieved was 97.18% for MG and 98% for CV for Dy doped ZnO nanoparticles. The degradation mechanism involved has been discussed in view of the reactive species determined from scavenging experiments.

Structural, optical, and magnetic properties of Co‐doped CeO2 thin films prepared by radio‐frequency magnetron sputtering

Co‐doped CeO2 (Ce1‐xCoxO2, x = 0, 0.03, and 0.06) thin films were prepared by radio‐frequency magnetron sputtering. The structural, optical, and magnetic properties of these films were characterized by X‐ray diffraction (XRD), Raman spectroscopy (Raman), atomic force microscopy (AFM), Fourier transform‐infrared spectroscopy (FT‐IR), spectroscopic ellipsometry (SE), and superconducting quantum interference magnetometer (SQUID). XRD and Raman studies revealed that all the films exhibited single phase of cubic fluorite structure, with highly (111) preferred orientation. No Co and Co‐related oxide was detected. Compared with undoped CeO2 films, the defect concentration of Co‐doped films increases. AFM images displayed that the film surface morphology is dependent on the Co‐doped content. The vibrational band assignment of undoped and Co‐doped CeO2 films was analyzed by FT‐IR. The energy dispersion optical constants (the refractive index n and the extinction coefficient k) of Ce1‐xCoxO2 thin films were obtained by analyzing the SE spectra in the ultraviolet and visible‐near infrared (UV–NIR) region (0.5–5.9 eV). The optical band gap energies Eg for these films were determined. The Eg values of the Ce1‐xCoxO2 thin films are 3.35, 3.27, and 3.25 eV, and the n values at wavelength of 632 nm are about 2.35, 2.38, and 2.42 for Co‐doped content x = 0, 0.03, and 0.06, respectively. SQUID measurements show that Co‐doped CeO2 films exhibit room temperature ferromagnetism, and the saturation magnetization (Ms) is 0.0051 and 0.0098 emμ/cm3 with the Co doping content x = 0.03 and 0.06, respectively. The ferromagnetism of Co‐doped CeO2 films belong to the intrinsic magnetism of the films.

The effect of Tb doping on the structural and magnetic properties of ZnO nanoparticles

Rare earth ions when incorporated in a semiconductor oxide lattice at nanoscale regime can affect the structural, optical as well as the magnetic properties of semiconductor host lattice. The change observed in the properties of the host lattice is due to the interaction between the dopant ions and host crystal. The structural and the morphological properties of Tb3+doped ZnO nanoparticles were studied using XRD, X-ray photoelectron spectroscopy and AFM studies. These experiments were performed on the doped nanoparticles to analyze the defects generated in the ZnO host lattice when a rare earth ion having ionic radii greater than that of Zn ion is doped in the ZnO nanoparticles. EDX measurement was used to estimate the elemental composition. An analysis of the XRD peak profile of the undoped and doped ZnO nanoparticle samples were done to evaluate the dislocation densities and the surface area. Both the parameters show an increase up to a certain concentration of Tb, which reveals the increase in the surface defects when Tb is introduced in ZnO host lattice. The strain calculated using Uniform deformation model from the XRD data also show an increase in the stress with the increase in Tb concentration which confirms the deformation of the host lattice. The magnetic study performed on the Pure ZnO nanoparticles shows a diamagnetic behaviour, while, Tb-doped ZnO nanoparticles exhibits room temperature ferromagnetism. The correlation between defects generated upon Tb-doping to the observed ferromagnetism, in the synthesized nanoparticles, has been reported.

Transition metal-doped chalcogenide perovskite magnetic semiconductor [formula omitted

Diluted magnetic semiconductors (DMSs) are an important type of materials for spintronic applications. Conventional DMSs are typically based on transition metal doped III-V and II-VI materials such as GaAs and CdSe. In this work, we show that a new DMS material can be realized by transition metal doping in BaZrS3, a prototypical chalcogenide perovskite semiconductor. Mn and Fe elements are doped into the BaZrS3 lattice with a concentration of up to 5%. In particular, Fe-doped BaZrS3 exhibits room temperature ferromagnetism.

Singular magnetic properties of porous anodized tin oxide ceramics

Porous SnO2 films were successfully prepared using pure tin foils by a convenient electrochemical anodization method in 0.5 M NaOH solutions. Interestingly, the same sample can simultaneously exhibit room temperature ferromagnetism, paramagnetism and diamagnetism. Moreover, the magnetic behavior is related to the direction of the applying magnetic field, showing obvious magnetic anisotropy. A reasonable explanation for this phenomenon was given by analyzing the morphology, magnetic characterization, and spectral analysis of the films, combined with the knowledge of solid physics. This research will be helpful in expanding the application of porous SnO2 films.

Morphology controlled synthesis of Fe and Mn co-doped In2O3 nanocubes and their Dopant-Atom effects on electronic structure and magnetic properties

Fe and Mn co-doped In2O3 single-phase cubic crystal structure nanocubes of uniform size and control over dopant concentration (In1.96Fe0.02Mn0.02O3, In1.94Fe0.02Mn0.04O3, In1.92Fe0.02Mn0.06O3 and In1.90Fe0.02Mn0.08O3) and microstructure were prepared using the hydrothermal-annealing technique. On a wider vision, we systematically investigated the influence of Fe and Mn co-doping in In2O3 through complementary experimental techniques and density functional theoretical (DFT) calculations to reveal the physical mechanisms involved in the origin of observed ferromagnetism. DFT calculations demonstrated that the substitution of surface indium atom by iron (FeIn) leads to impurity states on the top of In2O3 valence band maximum (VBM). Conversely, incorporation of interstitial (Mni) impurities in the host matrix without oxygen vacancies (VO) slightly shifts the top of the valence band and incorporation of interstitial Mn-impurity in the In2O3 (111) surface with oxygen vacancy does not provide noticeable changes in the electronic structure of the defective surface. High-resolution transmission electron microscopy measurements showed the formation of regular nanocubes in shape with 36.9–37.6 nm in average edge length. X-ray photoelectron spectroscopy investigations revealed that valence state of Fe mostly as Fe2+ and Fe3+ and Mn2+ for Mn atom in the In1.96Fe0.02Mn0.02O3, In1.94Fe0.02Mn0.04O3, In1.92Fe0.02Mn0.06O3 and In1.90Fe0.02Mn0.08O3. Magnetic studies exhibited room temperature ferromagnetism (RTFM) in the investigated samples with the high coercivity and saturation magnetization of 145.48 Oe and 0.023 emu/g, respectively for the In1.94Fe0.02Mn0.04O3. The origin of observed RTFM was described based on the bound magnetic polaron (BMP) model mechanism. DFT investigations demonstrated the clusters of impurities (FeIn-nMni) robust magnetic interactions within the cluster and between the clusters. Interestingly, only FeIn-nMni clusters contribute ferromagnetism observed in the investigated co-doped systems. Therefore, increasing the concentration of defects leads to the improvement of ferromagnetism. The comprehensive experimental and DFT investigations present new evidence to the observed ferromagnetism and electronic structure of Fe,Mn co-doped In2O3 nanocubes.

Microstructure, optical and magnetic properties of Zr-doped SnO synthesized by the hydrothermal method

Sn1−xZrxO was successfully synthesized by the one-step hydrothermal method. X-ray diffraction and Raman patterns reveal that the lattice distortion of SnO occurs with an increase in Zr concentration, and Zr ions are located at the substituted (ZrSn) and interstitial (Zri) sites successively. Scanning electron microscope and transmission electron microscope images showed that Zr concentration does not affect the well-crystalline nature of Sn1−xZrxO. However, the system's morphology changes from three-dimensional flowerlike to two-dimensional sheetlike. Furthermore, X-ray photoelectron spectroscopy and Raman spectra indicate that there are inherent oxygen vacancies (VO) in pure SnO lattice. UV–Visible absorption spectra show that the optical bandgap first decreases and then increases with Zr doping, which is explained by the sp–d exchange interactions in the case of ZrSn and the Burstein–Moss effect in the case of Zri. Additionally, Sn1−xZrxO samples exhibit room temperature ferromagnetism (RTFM), and the magnetic variation couples with the variation of the relative intensity of the Raman vibration modes. From the experimental results and the first-principles calculations, it can be seen that VO and the exchange interaction between Zr 4d and O 2p states are accountable for the RTFM of Sn1−xZrxO. Meanwhile, the lattice distortion and the Zr–O–Zr super-exchange interaction caused by excessive doping could decrease FM.

Growth of Co-doped ZnO thin films exhibiting room temperature ferromagnetism using a low-cost spray pyrolysis technique

Growth of Co-doped ZnO thin films exhibiting room temperature ferromagnetism using a low-cost spray pyrolysis technique

Role of tannic acid in desiging of electrically active and magnetic gold nanoparticles and enhanced photovoltaic performance of gold@titania photoanode in DSSC

We describe here in significance of tannic acid in obtaining size dependent electrochemically active and magnetic gold nanoparticles (GNPs). In this account, two types of GNPs (SCGNPs and SC-TAGNPs) were synthesized by using sodium citrate and sodium citrate-tannic acid as reducing agents, respectively. Highly monodispersed, uniformly distributed and small size GNPs were produced when tannic acid was used together with sodium citrate. SC-TAGNPs exhibited room temperature ferromagnetism while SCGNPs revealed diamagnetism. With higher anodic peak current and lower charge transfer resistance, the SC-TAGNPs exhibited better conductivity and electron transfer ability than SCGNPs. Mott-Schottky analysis revealed n-type semiconducting behavior of GC/SCGNPs & GC/SC-TAGNPs and showed positive shift in flat-band potential of GC/SC-TAGNPs compared to GC/SCGNPs suggesting better conductivity of SC-TAGNPs. Subsequently, SCGNPs and SC-TAGNPs were added to TiO2 nanoparticles to fabricate modified titania photoanodes (SCGNPs@TiO2 and SC-TAGNPs@TiO2) for dye-sensitized solar cells (DSSCs) application. With the use of TiO2, SCGNPs@TiO2 and SC-TAGNPs@TiO2 photoanodes, the short-circuit current density (JSC) was observed to be 2.18, 4.50 and 6.68 mA/cm2, while energy conversion efficiency (η) was found to be 0.75, 1.74 and 2.50%, respectively. The TiO2 photoanode employing SC-TAGNPs exhibited remarkably increased JSC and η by ∼48 and ∼44%, respectively, then SCGNPs modified photoanode.

Origin of magnetism in low energy Ni ion implanted ZnO thin films

ZnO films grown on Si(100) substrate through radio frequency (RF) sputtering are subjected to 100 keV Ni ion beam at different fluence (1×1016, 2.5×1016 and 5×1016 ions/cm2). High resolution X-ray diffraction revealed the increase in crystallite size and development of stress gradient in the ZnO thin films with the increasing Ni ion fluence. Ni implanted ZnO/Si(100) films exhibits room temperature ferromagnetism (RTFM) which is discussed via defect induced bound magnetic polaron model. Near-edge X-ray absorption fine-structure (NEXAFS) measurements at Ni L3,2-edge confirm the nature of implanted Ni ion inside the ZnO matrix. Further, NEXAFS at O K-edge revealed the onset of O(2p) with Ni(3d) orbital states, which is correlated with the observed RTFM.

Influence of defects on the structural, optical, photoluminescence and magnetic properties of Cr/Mn dual doped ZnO nanostructures

Cr (2%) doped ZnO and Cr, Mn (Cr = 2% and Mn = 2–4%) dual doped ZnO nanostructures were synthesized by chemical co-precipitation route. The hexagonal structure of Cr/Mn doped ZnO was not distorted by Mn doping and no secondary/impurity phases of Cr/Mn were detected in the XRD pattern. The reduced crystallite size at Mn = 2% is due to depression of growth rate and the dissimilarities between dopant and host ions and elevated crystallite size at 4% is accountable for the more defect sites in Zn-Cr-O lattice. The stable c/a ratio (~ 1.603) indicates that the hexagonal ZnO wurtzite structure of the synthesized composite is not affected by Mn substitution. The reduced crystallite size and the elevated UV–visible absorption at the higher wavelength side i.e., visible range at Mn = 2% recommended it for improved photocatalytic and efficient for solar cell applications. The broadening of energy gap at Mn = 2% is explained by Burstein-Moss (BM) band filling effect through energy level diagram. The presence of Zn-O-Cr/Mn bonding is confirmed by Fourier transform infra-red (FTIR) studies. The elevated PL emission and the intensity ratio between the green and blue emissions revealed the existence of more oxygen vacancies and oxygen related defect sites in Zn-Mn-Cr-O lattice. The exhibited room temperature ferromagnetism (RTFM) with strong magnetization in Cr, Mn doped ZnO is induced by both the oxygen vacancy mediated bound magnetic polarons (BMP) and the enhanced exchange coupling among the free electrons and local spin polarized electrons.

Room temperature d0 ferromagnetism in nitrogen doped WO3 for spintronic applications: A first-principles study

Using Density Functional Theory we predict that substitutional N doping in nonmagnetic WO3 exhibits room temperature ferromagnetism with 1.0 µB magnetic moment per defect. Induced moment is mostly contributed by 2p orbitals of N and O atoms. The Curie temperature from mean-field approximations and room temperature molecular dynamics simulations entrench that ferromagnetism persists at room temperature. The GGA results have been confirmed with more accurate hybrid functional (HSE06) calculations. As the facts that ferromagnetism persists at room temperature, structure remains stable at high temperature and have favourable formation energy signify that N doped WO3 can be used as spintronic devices.

Photoluminescence and intrinsic ferromagnetism of Fe doped zinc oxide

Zn1−xFexO nanoparticles with different doping concentration i.e. (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) were successfully synthesized via hydrothermal method. The crystal structure, morphology, optical and magnetic properties were studied by X-ray diffraction, field emission scanning electron microscope, UV–visible, photoluminescence spectra (PL) and vibrating sample magnetometer. The experimental results show that all the samples possess a single phase hexagonal wurtzite structure, no impurity phase was observed. The crystallite size decreases with the increase in Fe concentration. Optical absorption analysis by UV–visible exhibits a slight blueshift in the bandgap with increasing doping concentration. PL spectra shows that the emission peak in the UV region is absent for all the samples. All the emission peaks are in the visible region. Shifting of PL emission peaks is not observed indicating that the intrinsic defects are consistent. The magnetic observation indicated that all the samples including pure zinc oxide exhibit room temperature ferromagnetism (RTFM). The observed RTFM is attributed to the bound magnetic polaron that arises due to the presence of singly ionized oxygen vacancy (Vo) as indicated by PL spectra.

Magnetic Property of CoTbNi Ternary Alloy Thin Films

The structure and magnetic property of as prepared and post-annealed thin films of CoTbNi ternary alloy have been investigated. (Co0.85Tb0.15)1-xNix alloy thin films with x = (0.54, 0.63, 0.72, 0.81) were grown on Si-substrate by co-sputtering of Ni element and Co0.85Tb0.15 alloy using dc magnetron sputtering. These films have been crystallized in amorphous form, as confirmed by X-ray diffraction (XRD) measurement. The magnetization versus field measurements shows that these films exhibit room temperature ferromagnetism. The magnetic properties of these alloy films have a strong dependency on the Ni concentrations. It is observed that the saturation magnetization and coercivity of these alloy thin films decreases with increase of Ni content of the films. One of the striking features was the observation of perpendicular magnetic anisotropy (PMA) for x = 0.63 and 0.72 thin films. However, the observed PMA disappears upon post-annealing of the films. The M-T measurement shows that the ferromagnetic transition temperatures of these materials are much higher than the room temperature.

REFINEMENT ANALYSIS, PHOTOLUMINESCENCE AND MAGNETIC PROPERTIES OF Zn1-XMnXO (x = 0.00, 0.01, 0.02, 0.03 & 0.04) NANOPARTICLES SYNTHESIZED BY COMBUSTION TECHNIQUE

Zn1-XMnXO (x = 0.0, 0.01, 0.02, 0.03 & 0.04) nanoparticles were fabricated through a simple combustion method and their structural, morphological, chemical, optical, photoluminescence and magnetic properties were systematically analyzed. X-ray diffraction (XRD) and Rietveld refinement (RR) analysis studies divulged that, the synthesized nanoparticles exhibited the hexagonal structure without any impurity phase. Morphology studies revealed that the synthesized nanoparticles were nearly spherical in shape with uniform size distribution. A clear Blue shift was recognized in the ZnO nanoparticles when doped with Mn ions. The photoluminescence (PL) spectra of all the synthesized nanoparticles exhibited the same emissions and PL intensity diminished with increase in Mn doping concentration. All the synthesized nanoparticles exhibited room temperature ferromagnetism (RTFM) and Zn1-XMnXO(x=0.02) nanoparticles displayed better ferromagnetic property than other compositions. The captivate properties of the ZnO: Mn nanoparticles may more useful for optoelectronic and spintronic applications.

Novel Zr–Cu–Fe nanocomposite metal oxides: structural, magnetic and composition activity effects on photodegradation of phenols

Pure CuFe2O4 nanoparticles were synthesized using sol–gel method technique. Effect of Zr/Cu substitution (Cu1−xZrx, where x = 0.25, 0.50, 0.75, and 1.00) on the structural, morphological, and magnetic properties was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), infrared Fourier transform infrared (FTIR), and vibrating sample magnetometer (VSM). The photocatalytic behavior of pure CuFe2O4 as well Zr-substituted samples was investigated for degradation of phenol in aqueous solution in the presence of ultraviolet irradiation. The XRD results of pure CuFe2O4 confirmed the formation of single tetragonal structure phase, while introducing zirconium in the structural composition resulted in a decrease in the crystallinity and gradual disappearance of the cuprospinel phase accompanied with appearance of single metal oxides species (Fe2O3, ZrO2, Cu4O3). Based on the scanning (SEM–EDX), the samples consist of agglomerated particles with varying sizes and shapes related to their compositions. The magnetic hysteresis loops of all samples exhibited room temperature ferromagnetism with variable shapes, saturation magnetization, and coercivity values. All samples showed a significant photocatalytic activity when irradiated with ultraviolet light. The highest photocatalytic efficiency (92%) for phenol degradation was achieved through the 25% Zr-substituted sample under irradiation time of 150 min.

Structural, magnetic and photoluminescence behavior of Ni/Fe doped ZnO nanostructures prepared by co-precipitation method

Un-doped and Ni/Fe-doped ZnO nanostructures were synthesized by co-precipitation route. The variation in crystallite size and lattice parameters by Ni/Fe doping is discussed by the dissimilarity in their ionic radius and the generation of defect states. The higher energy gap in Fe-doped Zn0.97Ni0.03O is described by the generation of oxygen related defects. The shifting of IR frequency by Ni/Fe-doping confirmed the Ni/Fe ions are replaced at tetrahedral sites instead of octahedral co-ordination. The high intensity green emission at ∼ 524 nm from PL study confirmed the increased oxygen vacancies related defects in Ni, Fe dual doped ZnO. Though the entire samples exhibited room temperature ferromagnetism (RTFM), Ni, Fe dual doped ZnO showed the strong ferromagnetism due to the existence of the oxygen vacancy mediated bound magnetic polarons (BMP).