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1.
We had prepared Mn-doped ZnO and Li, Mn codoped-ZnO films with different concentrations using spin coating method. Crystal structure and magnetic measurements demonstrate that the impurity phases (ZnMnO3) are not contributed to room temperature ferromagnetism and the ferromagnetism in Mn-doped ZnO film is intrinsic. Interesting, saturated magnetization decreases with Mn or Li concentration increase, showing that some antiferromagnetism exists in the samples with high Mn or Li concentration. In addition, Mn0.05Zn0.95O film annealed in vaccum shows larger ferromagnetism than the as-prepared sample and more oxygen vacancies induced by annealing in reducing atmosphere enhance ferromagnetism, which supports the bound magnetic polaron model on the origin of room temperature ferromagnetism. 相似文献
2.
采用共沉淀方法制备了名义组分为Zn1-xMnxO(x=0.001,0.005,0.007,0.01)的Mn掺杂的ZnO基稀磁半导体材料,并研究了在大气气氛下经过不同温度退火后样品的结构和磁性的变化.结果表明:样品在600℃的大气条件下退火后, 仍为单一的六方纤锌矿结构的ZnO颗粒材料;当样品经过800℃退火后,Mn掺杂量为0.007,0.01的样品中除了ZnO纤锌矿结构外还观察到ZnMnO3第二相的存在.磁性测量表明,大气条件下600℃退火后的样品,呈现出室温铁磁性;而800℃退火后的样品,其室温铁磁性显著减弱,并表现为明显的顺磁性.结合对样品的光致发光谱的分析,认为合成样品的室温铁磁性是由于Mn离子对ZnO中的Zn离子的替代形成的.
关键词:
ZnO
掺杂
稀磁半导体
铁磁性 相似文献
3.
Cubic ZnMnO3 powder in the form of well-crystalline nanoflakes have been synthesized at low temperatures from a nitrate precursor. The electrical properties of cubic ZnMnO3 samples have been established by DC resistivity (ρ) and thermo-electric power (Seebeck coefficient) measurements on a pressed pellet. The material exhibits insulator behavior with 0.7 eV acceptor ionization energy in the measured temperature range of 170-300 K. The thermo-electric power indicates a positive sign of the charge carriers. The obtained material exhibits a superparamagnetic signature with a blocking temperature of 9 K and the ZFC-FC splitting temperature of 15 K. 相似文献
4.
Yanyan Wei Denglu Hou Shuang Qiao Congmian Zhen Guide Tang 《Physica B: Condensed Matter》2009,404(16):2486-2488
Zn0.95−xCo0.05CuxO powders have been synthesized by the sol-gel method and the structural, magnetic and electrical properties of the powders have been investigated. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) indicate that the Co ions do not change the ZnO wurtzite structure. Magnetic measurements indicate that Co doping can induce room temperature (RT) ferromagnetism and the addition of Cu to the powders further increases the magnetic moment per Co ion. The effects of the introduction of Cu as an acceptor dopant in the host matrix are further studied using resistance measurements. It is demonstrated experimentally that acceptor doping plays an important role in realizing dominant ferromagnetic ordering in Co doped ZnO powders. 相似文献
5.
A. I. Smirnov V. N. Glazkov A. N. Vasil’ev L. I. Leonyuk S. M. Coad D. McK. Paul G. Dhalenne A. Revcolevschi 《JETP Letters》1996,64(4):305-311
Magnetic resonance at frequencies 22–75 GHz is investigated in pure single-crystalline CuGeO3 in the temperature range 1.2–25 K. At temperatures below 4 K the magnetic resonance line splits into four spectral components.
The line close to the ESR of the paramagnetic phase is associated with impurities or defects. The other three lines have the
same intensity in different samples and are apparently characteristic for pure single crystals at low temperature. An antiferromagnetic
resonance with two resonance absorption branches and a spectrum characteristic for an antiferromagnet with easy, average,
and hard anisotropy axes was observed and investigated in the Néel compound Cu0.98Zn0.02GeO3 with diamagnetic dilution of the spin subsystem.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 4, 277–282 (25 August 1996) 相似文献
6.
Amorphous copper-doped ZnO thin films (ZnO:Cu) prepared on glass substrates by the radio-frequency magnetron co-sputtering have been investigated. Magnetic measurements indicated that the amorphous ZnO:Cu thin films were ferromagnetic at room temperature and the saturation magnetization was much higher than that of the polycrystalline films. X-ray diffraction results showed there was no Cu2O phase in amorphous ZnO:Cu films, which might be the reason for the high magnetic moment of the films. On the other hand, the high saturation magnetization of the amorphous ZnO:Cu films could also attribute to that there was no limit of solid solubility of Cu in amorphous ZnO solvent. The X-ray photoelectron spectroscopy study of the amorphous ZnO:Cu thin films reveal that copper was in Cu2+ chemical state. 相似文献
7.
C.S. Xiong Y. Zeng J. Zhang L. Zhang X.W. Cheng L.J. Li 《Physica B: Condensed Matter》2008,403(18):3266-3270
Composite samples (1−x)La0.7Ca0.2Sr0.1MnO3(LCSMO)+x(ZnO) with different ZnO doping levels x have been investigated systematically. The structure and morphology of the composites have been studied by the X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The XRD and SEM results indicate that no reaction occurs between LCSMO and ZnO grains, and that ZnO segregates mostly at the grain boundaries of LCSMO. The magnetic properties reveal that the ferromagnetic order of LCSMO is weakened by addition of ZnO. The results also show that ZnO has a direct effect on the resistance of LCSMO/ZnO composites, especially on the low-temperature resistance. With increase of the ZnO doping level, TP shifts to a lower temperature and the resistance increases. It is interesting to note that an enhanced magnetoresisitance (MR) effect for the composites is found over a wide temperature range from low temperature to room temperature in an applied magnetic field of 3 kOe. The maximum MR appears at x=0.1. The low field magnetoresistance (LFMR) results from spin-polarized tunneling. However, around room temperature, the enhanced MR of the composites is caused by magnetic disorder. 相似文献
8.
K. Sharma Sher Singh C.L. Prajapat S. Bhattacharya Jagannath M.R. Singh S.M. Yusuf G.P. Kothiyal 《Journal of magnetism and magnetic materials》2009,321(22):3821-3828
The magnetic properties of 25SiO2–50CaO–15P2O5–(10−x)Fe2O3−xZnO (where x=0, 2, 5 mol%) glass and glass-ceramics have been studied. These glasses are prepared by melt quench technique and heat treated at 800 °C for 6 h. Electron Spectroscopy for Chemical Analysis (ESCA) revealed that the fraction of non-bridging oxygen decreases with the increase in zinc oxide content. Evolution of crystalline phases in glass-ceramics has been studied by X-ray diffraction (XRD). The microstructure as seen by scanning electron microscopy (SEM) exhibits formation of nanosize particles. Effect of controlled heat treatment on magnetic properties was studied by means of a Superconducting Quantum Interference Device (SQUID) magnetometer. Mössbauer spectroscopy at room temperature was also carried out to determine the state of iron ions in glasses and glass-ceramics. Isomer shift values of the glasses suggest that Fe3+ and Fe2+ are in tetrahedral coordination. The analysis of the glass without ZnO shows about 58 wt% of total iron ions is in the Fe3+ state. The samples on heat treatment show improved magnetic properties due to the formation of magnetic nanoparticles. Magnetic studies revealed the relaxation of magnetic particles and the increase in saturation magnetization with addition of 2 mol% ZnO. Increase in ZnO content results in decrease in the strength of dipolar interactions. 相似文献
9.
Magnetic resonance and microwave impedance are studied in a highly doped La0.8Sr0.2MnO3 manganite near the Curie temperature. A splitting of the resonance line is observed in the temperature region 6° below the temperature corresponding to the maximum impedance at zero magnetic field. The microwave impedance exhibits a hysteretic behavior in increasing and decreasing temperature runs with jumps at the ends of a 2°-wide temperature interval. The splitting of magnetic resonance occurs immediately above the temperature corresponding to the impedance jump in zero magnetic field. The jumps and the hysteretic behavior of the impedance are interpreted as a manifestation of the magnetic structure phase transition of the first order. 相似文献
10.
Niko Guskos Spiros Glenis Janusz Typek Grzegorz Zolnierkiewicz Pawel Berczynski Kamil Wardal Aleksander Guskos Daniel Sibera Dariusz Moszyński Witold Lojkowski Urszula Narkiewicz 《Central European Journal of Physics》2012,10(2):470-477
Fine particles of ZnFe2O4 were synthesized by a wet chemical method in the (80 wt.% Fe2O3 + 20 wt.% ZnO) system. The morphological and structural properties of the mixed system were investigated by scanning electron microscopy, X-ray diffraction, inductively coupled plasma atomic emission, and X-ray photoelectron spectroscopy. The major phase was determined to be the ZnFe2O4 spinel with particle size of 11 nm. The magnetic properties of the material were investigated by ferromagnetic resonance (FMR) in the temperature range from liquid helium to room temperature. A very intense, asymmetric FMR signal from ZnFe2O4 nanoparticles was recorded, which has been analyzed in terms of two Callen-lineshape lines. Temperature dependence of the FMR parameters was obtained from fitting the experimental lines with two component lines. Analysis of the FMR spectra in terms of two separate components indicates the presence of strongly anisotropic magnetic interactions. 相似文献
11.
Libing Duan Xiaoru Zhao Jinming Liu Wangchang Geng Haiyan Xie Shuai Chen 《Journal of magnetism and magnetic materials》2011,323(18-19):2374-2379
We present a systemic study on the structural, thermal and magnetic properties of Zn1?xMnxO nanoparticles synthesized by a combustion method with heavily Mn doping concentrations x=0.05, 0.15 and 0.25. The structural evolutions in relation to the possible variation of the Mn oxidation state and dopant induced tiny Zn2MnO4/Mn2O3 and ZnMnO3/MnO2 impurities, which have not been detected by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM), were investigated by means of X-ray photoelectron spectroscopy (XPS), Raman scattering spectra, thermo-gravimetric analysis (TGA) and magnetic measurements. It is evidenced that the optimal Mn concentration x in ZnO to grow single phase Zn1?xMnxO should be below the cation percolation threshold xp (about 0.125), which is the basis to form real diluted magnetic semiconductors (DMSs). 相似文献
12.
Magnetic MFe2O4 (M=Co, Ni, Zn) nanocrystals with a diameter about 30 nm and a nearly spherical shape were synthesized via a simple hydrothermal approach. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy have been used to investigate the as-prepared magnetic MFe2O4 (M=Co, Ni, Zn) nanocrystals. Magnetic properties of the as-prepared samples have been detected by a vibrating sample magnetometer at room temperature and the results show that the as-prepared magnetic MFe2O4 nanocrystals are a type characteristic of superparamagnetic materials. These superparamagnetic nanocrystals are believed to be promising for wide engineering applications, such as drug delivery, bioseparation, and magnetic resonance imaging. 相似文献
13.
Magnetic properties of orthorhombic incommensurate antiferromagnet β-KMnCl3 have been studied as a function of temperature down to 0,5K and in magnetic fields up to 70 k0e. The exchange parameters were estimated with molecular-field theory. Magnetic field behaviour of β-KMnCl3 is in accordance with change of magnetic structure from helical into fan structure and then into induced ferromagnetic state. The Neel temperature decreases with increase magnetic field overage 0,05K on 1 k0e. 相似文献
14.
A. M. Balagurov I. A. Bobrikov S. V. Sumnikov V. Yu. Yushankhai N. Mironova-Ulmane 《JETP Letters》2016,104(2):88-93
Structural and magnetic phase transitions in NiO and MnO antiferromagnets have been studied by high-precision neutron diffraction. The experiments have been performed on a high-resolution Fourier diffractometer (pulsed reactor IBR-2), which has the record resolution for the interplanar distance and a high intensity in the region of large interplanar distances; as a result, the characteristics of both transitions have been determined simultaneously. It has been shown that the structural and magnetic transitions in MnO occur synchronously and their temperatures coincide within the experimental errors: Tstr ≈ Tmag ≈ (119 ± 1) K. The measurements for NiO have been performed with powders with different average sizes of crystallites (~1500 nm and ~138 nm). It has been found that the transition temperatures differ by ~50 K: Tstr = (471 ± 3) K, Tmag = (523 ± 2) K. It has been argued that a unified mechanism of the “unsplit” magnetic and structural phase transition at a temperature of Tmag is implemented in MnO and NiO. Deviation from this scenario in the behavior of NiO is explained by the quantitative difference—a weak coupling between the magnetic and secondary structural order parameters. 相似文献
15.
Diluted Magnetic Semiconductors offer potential applications for spintronics. In this respect, Co-doped ZnO films are particularly interesting due to their Curie temperature. However, the origin of ferromagnetism is controversial. High quality Co-doped ZnO thin films have thusly been grown using the pulsed laser deposition technique on (001) Al2O3 substrates. Two series were made. In the first one, the films are grown using metallic targets whereas in the second one, the films are synthesized from ceramic targets. Detailed characterizations have been performed and a comparison have been made, in light of the literature. 相似文献
16.
Chengbin Jing Yingjing Jiang Junhao Chu 《Journal of magnetism and magnetic materials》2010,322(16):2395-1306
Mn-doped ZnO samples with 5%, 20% and 40% nominal Mn concentrations were prepared in the presence of ethyl acetoacetate under solvothermal conditions. UV absorption spectroscopic analysis discloses that chemical modification was achieved by reaction of Zn or Mn precursor with ethyl acetoacetate in ethanol medium. XRD and HRTEM characterizations indicate that ZnMnO3 impurity phase was formed in the 20% and 40% Mn-doped ZnO samples while no secondary phase was present in the 5% Mn-doped sample. The 5% Mn-doped sample consists of spheroid-like particles with size of 10-50 nm and has a real Mn concentration of 3.2%. Ferromagnetism and paramagnetism coexist in the 5% Mn-doped ZnO sample at room-temperature, which may arise from ferromagnetic exchange interaction as well as small secondary phases. The 20% and 40% Mn-doped samples show large paramagnetic effects at room temperature. Small paramagnetic secondary phases and clustering of Mn are probably responsible for this. 相似文献
17.
Guangqing Pei Changtai Xia Shixun Cao Jungang Zhang Feng Wu Jun Xu 《Journal of magnetism and magnetic materials》2006
Polycrystalline Zn1−xNixO diluted magnetic semiconductors have been successfully synthesized by an auto-combustion method. X-ray diffraction measurements indicated that the 5 at% Ni-doped ZnO had the pure wurtzite structure. Refinements of cell parameters from powder diffraction data revealed that the cell parameters of Zn0.95Ni0.05O were a little bit larger than ZnO. Transmission electron microscopy observation showed that the as-synthesized powders were of the size ∼60 nm. Magnetic investigations showed that the nanocystalline Zn0.95Ni0.05O possessed room temperature ferromagnetism with the saturation magnetic moment of 0.1 emu/g (0.29 μB/Ni2+). 相似文献
18.
The 57Fe Mössbauer technique has been used to investigate the effect of zinc oxide substitution in (25???x)MnO–xZnO–15Fe2O3–60B2O3 glass system (x?=?0, 5, 10, 15 and 20 mol% of ZnO ). Mössbauer absorption spectra for all the samples recorded at room temperature suggest the existence of the two paramagnetic quadrupole doublets. The observed variations in hyperfine parameters have been explained on the basis of cations distribution and exchange interaction at the lattice sites and it is concluded that B–B interaction increases while the metal–metal interaction decreases due to replacement of manganese oxide by zinc oxide. These results suggest that the present glass system exhibits a paramagnetic behaviour that changes towards the weak paramagnetic when manganese oxide was replaced with zinc oxide. 相似文献
19.
We report the microstructural and magnetic properties of transition (3d) and rare earth (4f) metal substituted into the Ax:Zn1?xO (A=Mn, Gd and Mn/Gd) nanocrystal samples synthesized by solgel method. The structural properties and morphology of all samples have been analysed using X-ray diffraction (XRD) method and scanning electron microscopy. The impurity phase in the XRD patterns for all samples is not seen, except (Mn/Gd):ZnO sample where a very weak secondary phase of Gd2O3 is observed. Due to the large mismatch of the ionic radii between Mn2+ and Gd3+ ions, the strain inside the matrix increases, unlike the crystallite size decreases with the substitution of Mn and Gd into ZnO system. A couple of additional vibration modes due to the dopant have been observed in Raman spectrum. The magnetic properties have been studied by vibrating sample magnetometer. The magnetic hysteresis shows that Mn:ZnO and Gd:ZnO have soft ferromagnetic (FM) behaviour, whereas (Mn/Gd):ZnO has strong FM behaviour at room temperature (RT). The enhancement of ferromagnetism (FM) in (Mn/Gd):ZnO sample might be related to short-range FM coupling between Mn2+ and Gd3+ ions via defects potential and/or strain-induced FM coupling due to the expansion lattice by doping. The experimental results indicate that RTFM can be achieved by co-substitution of 3d and 4f metals in ZnO which can be used in spintronics applications. 相似文献
20.
Lanthanum-strontium manganites doped with zinc are studied by the method of electron magnetic resonance. Nano-objects with ferromagnetically correlated spins, which behave themselves like superparamagnetic particles in the magnetic resonance spectrum, have been found in the paramagnetic phase. The temperature dependences of the resonance magnetic field and magnetic resonance linewidth for La1 ? x Sr x Mn0.925Zn0.075O3 ceramic samples at temperatures ranging from 100 to 340 K have been analyzed on the basis of the Raikher-Stepanov theory of superparamagnetic particles. The magnetic moment, anisotropy field, and characteristic size of the regions of the ferromagnetically correlated spins have been determined. 相似文献