Mn掺杂ZnO稀磁半导体的化学合成及磁性研究

采用化学方法制备了名义组分为Zn0.993Mn0.007O的Mn掺杂ZnO稀磁半导体材料,并研究了退火温度(Ts＝400,600,800℃)对其结构和磁性的影响.结果表明:在退火温度低于600℃条件下,合成的样品为单一纤锌矿结构的ZnO颗粒材料;当退火温度为800℃时,合成的样品中除了纤锌矿结构ZnO外还观察到ZnMnO3第二相的存在.磁性研究表明:经过600℃退火后的样品,其室温铁磁性最强,而经过800℃退火后的样品,其铁磁性几乎消失,并表现为增强的顺磁性.结合对样品的Raman光谱和紫外-可见吸收光谱的分析,表明Mn元素进入了ZnO晶格中并替代了ZnO中的Zn离子. 样品的室温铁磁性是源于(Zn,Mn)O的本征特性,并排除了样品中第二相导致其具有室温铁磁性的可能性.     

Synthesis and Physical Properties of Mn Doped ZnO Dilute Magnetic Semiconductor Nanostructures

Mn doped ZnO nanostructures have been prepared using low temperature simple, quick, and versatile synthesis approach. The structural, microstructural, and vibrational investigations reveal that as prepared nanostructures with low Mn doping concentration have single hexagonal phase and are grown along the preferred c-axis. The X-rays photoelectron spectroscopy demonstrates that the Mn ions are in mixed oxidation states for high doping concentration of Mn, while are in 2+ oxidation state for low concentration into ZnO lattice. The photoluminescence spectrum (PL) exhibits a significant red-shift of 22 nm in the optical band gap of doped ZnO and shows the improved luminescence properties, which makes it potential for its use in the photocatalyst, optoelectronics and solar cell nanodevices. Furthermore, the magnetic measurement of Mn doped ZnO nanostructures exhibits the ferromagnetism at room temperature.     

Structural and Magnetic Properties of (Al/Mg) Co-doped Nano ZnO

The doped ZnO systems Zn_1?x?y Mg _x Al _y O (ZMAO) (x=0, 0.05, 0.1 and y=0, 0.05 and 0.1) were prepared as polycrystalline nanoparticle by a simple sol–gel process. Structural and microstructural analyses were carried out applying X-ray diffraction (XRD) and Rietveld method. Analysis showed that Mg²⁺ and Al³⁺ replace Zn²⁺ substitutionally yielding ZMAO single phase. Replacing Zn⁺² affects the lattice parameters in opposite ways, the parameter c decreases while a increases with an overall decrease in the ratio c/a, which deviates the ZMAO lattice gradually from the wurtzite hexagonal structure. The magnetization versus temperature was measured with zero-field cooled (ZFC) and field cooled (FC) at different applied fields. Also, measurement of magnetization versus applied field was carried out at different temperatures. The system exhibits ferromagnetic properties at room temperature. The saturation magnetization increases as Al doped amount increases.     

The Effects of Mn Substitution on Magnetization Reversal Properties in Gd0.7Ca0.3MnO3

Low temperature magnetization in polycrystalline Gd_0.7Ca_0.3Mn_1?x M _x O₃ (M=Cr, Ga, Ru; x=0, 0.2) has been investigated. The samples were prepared via the conventional solid state reaction method. For all the samples, the paramagnetic to ferrimagnetic (PM-FiM) transition temperature (say T _max) can be well defined from the temperature dependent ac susceptibility data. The negative magnetization suppresses due to 20 % Cr or Ga doping at the Mn site. On the other hand, below the compensation temperature (T _comp), the nature of the Ru doping sample is almost similar to that of undoped Gd_0.7Ca_0.3MnO₃. The nonmagnetic Ga doping drastically reduces magnetization and T _max shifts to a lower temperature. However, Ru and Cr doping increase the value of T _max. The network of canted Mn³⁺/Mn⁴⁺ moments changes with the substitution of Cr, Ga, and Ru at the Mn site giving rise to the variation of the internal magnetic moment. Thus, the antiparallel coupling of the Gd moments with Mn/M changes and affects the low temperature magnetization reversal properties.     

Magnetic and optical properties of Mn doped ZnO nanocrystalline films

We have investigated the properties of Mn-doped ZnO nanocrystalline film growing on zinc foil by the hydrothermal method. X-ray photoelectron spectroscopy shows that the manganese ions exist as Mn2+ in the film. From UV-vis spectra, we observe a red shift in wavelength of absorption and greater reflectivity due to the Mn ion incorporation in ZnO lattices. The photoluminescence spectrum of the Mn-doped ZnO film shows two strong new blue peaks centered at 424 nm and 443 nm, besides the UV emission peak owing to the band gap of ZnO semiconductor. The magnetic property of the Mn-doped ZnO exhibits a room temperature ferromagnetic characteristic with a saturation magnetization (Ms) of 0.3902 x 10(-3) emu/cm3 and a coercive field of 47 Oe. We suggest that the blue emission of the Mn-doped ZnO film corresponds to the electron transition from the level of interstitial Zn and Mn to the valence band. The defects brought about by Mn ion incorporation are the main cause of the room temperature ferromagnetic property.     

Low-Temperature Magnetic Properties of Vanadium-Doped ZnO Nanoparticles

Low-temperature magnetic study of transition metal-doped ZnO nanoparticles tends to spring ambiguities of magnetic phases due to defect states, environment of doped ions, and anisotropy. Interestingly, vanadium doping in ZnO brings out versatile magnetic ordering which offers more room for basic understanding of the underlying mechanism. Vanadium-doped ZnO nanoparticles are prepared using a simple cost-effective approach of solution combustion method. Macroscopic and microscopic aspects of the samples have been unraveled using structural and morphological studies with the implications on the exhibited magnetic behavior. Development of antiferromagnetic, ferromagnetic, and ferrimagnetic interactions in the material illustrated by low-temperature magnetic measurements preludes the possible interplay of dopant-initiated defect correlation and morphological and interfacial secondary phases. The grain boundary reformation due to vanadium in the ZnO nanograins is exploited through a systematic correlation of structural and morphological studies in order to gain more insight into the portrayed magnetic signatures.     

射频溅射氧化锌薄膜晶体结构和电学性质

利用射频磁控溅射ZnO:Al(3wt%)陶瓷靶材制备ZAO薄膜,利用X射线衍射仪和霍尔测试仪分析了不同衬底温度和工作压强对薄膜结构和电学性能的影响.结果表明,随工作压强的降低,薄膜(002)优先取向增强,迁移率逐渐增大,当工作压强为0.2 Pa、衬底温度为200℃时,薄膜的电阻率为1.4×10-3Ω·cm.     

Mn、Li共掺ZnO稀磁半导体的制备与铁磁性研究

采用固相陶瓷烧结法制备了Mn、Li共掺的ZnO稀磁半导体材料,实现了室温铁磁性。分别用XRD、XPS和VSM对各样品进行了结构测量和磁性能测量,分析了Mn、Li掺杂浓度对ZnO基稀磁半导体的影响。结果表明,在相同的外磁场下,随着Mn掺杂浓度的增加,陶瓷的磁化强度增大。但较高的Li掺杂浓度可能会形成更多填隙离子,减少空穴浓度,最终使材料的室温铁磁性变差。     

Tuning the Microstructural and Magnetic Properties of ZnO Nanopowders through the Simultaneous Doping of Mn and Ni for Biomedical Applications

Undoped and Mn+Ni doped Zn O nanopowders were synthesized using a simple soft chemical route by varying the Ni doping level(1, 3, 5 and 7 at.%) and keeping the Mn doping level(10 at.%) constant. X-ray diffraction studies reveal that the incorporated Ni2+ions form a secondary phase of cubic Ni O beyond the Ni doping level of 3 at.%, which is also confirmed by Fourier transform infrared spectroscopy. The band gap of the nanopowders increases(from 3.32 to 3.44 e V) up to 3 at.% of Ni doping and decreases with further doping. Zn O:Mn:Ni nanopowders with 3 at.% of Ni concentration exhibit good antibacterial efficiency. The variation in the size of the nanoparticles, as observed from the TEM images and hydroxyl radicals as evidenced from the photoluminescence results, clearly substantiate the discussion on the antibacterial efficiency of the synthesized nanopowders. Magnetic properties of the synthesized nanopowders were studied using a vibrating sample magnetometer, and the results showed that the doping of Mn and Ni largely influences the magnetic properties of Zn O nanopowders.     

Magnetic Properties and Magnetocaloric (MC) Effects in the Antiferromagnetic Gd2NiGa3 Compound

Journal of Superconductivity and Novel Magnetism - The magnetocaloric (MC) properties in various magnetic materials were well determined within last three decades due to its own potential...     

Mn、Co掺杂ZnO薄膜结构及发光特性研究

利用脉冲激光沉积(PLD)方法在Si(100)衬底上制备了ZnO、Zn0.8Mn0.2O、Zn0.8Co0.2O薄膜.薄膜的晶体结构和表面形貌采用X射线衍射仪和原子力显微镜测试.表明薄膜具有明显的c轴择优生长取向,薄膜表面较为平整,颗粒尺寸在纳米量级,薄膜中晶粒的生长模式为"柱状"模式.此外,Mn、Co掺入后,薄膜的X射线衍射峰有小角度偏移,这与 Mn2 、Co2 离子半径有关.PL谱显示Mn、Co掺杂ZnO薄膜的蓝、绿发光峰的位置相对纯的ZnO薄膜没有改变,还出现了紫外发光峰,其中Mn掺杂的蓝、绿光峰的强度减弱,Co掺杂的蓝光峰强度减弱,绿光峰强度增强.这是因为Mn、Co掺入改变了ZnO本征缺陷的浓度,发光峰的强度也随之而改变.     

过渡金属掺杂ZnO稀磁半导体的发光特性

ZnO是一种宽带隙Ⅱ-Ⅵ族半导体,具有良好的光电耦合特性和稳定性,在光、电、磁功能集成等新型器件方面可获得重要应用.近来的研究表明,过渡金属掺杂的ZnO基半导体有望成为实现高居里温度稀磁半导体的候选材料,是目前研究的热点.总结了近几年人们在Fe、Co、Ni、Cu、Mn等过渡金属掺杂的ZnO基稀磁半导体的发光特性研究结果,讨论了过渡金属掺杂后ZnO中观察到的可见发光机制,分析认为过渡金属掺杂ZnO的可见光发射主要与这些发光过渡金属引入后所产生的缺陷有关,而紫外发光峰的变化则与过渡金属掺入后ZnO晶体质量与禁带宽度的改变相关.     

Structural and Optical Properties of Co-Doped ZnO Thin Films

Co-doped zinc oxide thin films (Zn_1–xCo_xO) have been deposited on c-plane sapphire substrates by dual-beam pulsed laser deposition. The films have lattice parameters similar to that of ZnO, and the lattice parameters are closely distributed. The films grew along a preferred direction, following the epitaxial relationship Zn_1–xCo_xO (0001)substrate (0001). Excitonic emission was suppressed at higher Co-dopant concentration in ZnO because of increase in the distortion of host lattice and defects. When more Zn is replaced by Co, more impurity levels are developed within the bandgap, and more defect are generated. Under our experimental conditions, the bandgap of the films tends to increase with increasing dopant concentration.     

Mn Clusters in Nanoporous Carbon: Magnetic Properties

Technical Physics Letters - A method is described for introducing Mn clusters into nanoporous carbon. The resulting magnetic properties of composite samples of this kind are demonstrated in the...     

Structural and Magnetic Properties of Various Ferromagnetic Nanotubes

The structural and magnetic properties of ferromagnetic nanotubes fabricated by a low cost electrodeposition method are investigated. The fabrication of various elemental ferromagnetic materials are described, such as Fe, Co, and Ni, and ferromagnetic alloys, such as NiFe, CoPt, CoFeB, and CoCrPt nanotube arrays, in aluminum oxide templates and polycarbonate membranes with different diameters, wall thicknesses, and lengths. The structural, magnetic, and magnetization reversal properties of these nanotubes are investigated as a function of the geometrical parameters. The angular dependence of the coercivity indicates a transition from the curling to the coherent mode for the ferromagnetic nanotubes. The results show that nanotube fabrication allows the outer and inner diameter, length, and thickness of the nanotubes to be tuned systematically. The magnetization processes of ferromagnetic nanotubes are influenced by the wall thickness.     

First Principles Study on the Effects of Cu Doping on the Magnetic Moment and Electronic Properties of V-Doped ZnO

The CASTEP program was used to study the effects of Cu on the structure, magnetic moment and electronic properties of V-doped ZnO. The calculated enthalpies showed that the Cu atoms were inclined to stay near the V atoms. Cu neutralized the delocalized electrons in V-doped ZnO. Cu also suppressed the magnetic moments of Zn and O more than those of the V ions. The different amounts of suppression caused the moments to concentrate on the V atoms. The magnetic moments decreased in Cu and V co-doped ZnO. The suppressions of the magnetic moments and concentrations of the Cu atoms were verified with density of states calculations. The states showed that Cu increased the conduction in V-doped ZnO. The calculated spin isospheres showed that Cu improved the concentration of the magnetic moments on the V sites. The improved concentration enhanced the performance of diluted magnetic semiconductors based on V-doped ZnO. These results help in understanding the role of Cu in V-doped ZnO. They also provide a reference for preparing diluted magnetic semiconductors based on V-doped ZnO