Effect of Annealing Temperature on Structural and Magnetic Properties of Zn0.94Co0.05Cu0.01O

The doped ZnO system Zn_0.94Co_0.05Cu_0.01O (ZCCO) was prepared as a nano-polycrystalline by a simple sol–gel process, then air annealed at different temperatures. Applying X-ray diffraction (XRD) and the Rietveld method, structural analysis showed that Co and Cu replace Zn substitutionally yielding ZCCO single phase. The refined u-fractional coordinate of Zn increases monotonically by an annealing temperature from 0.3546 at 500 °C reaching 0.3722 at 800 °C, very near from the ideal value 0.375. The Zn tetrahedrons become more symmetric and the distortion is gradually relieved by annealing up to 800 °C. Annealing at 900 °C introduces tetrahedron distortion in an opposite way. The zero field cooled (ZFC) and field cooled (FC) magnetization versus the temperature at different applied fields and the magnetization versus the applied field at different temperatures were carried out. The system exhibits a ferromagnetic behavior at room temperature. As the annealing temperature increases from 550 to 900 °C, the saturation magnetization at 300 K increases from 0.0507 to 0.1088 emu/g.     

Annealing Effect in GaDyN on Optical and Magnetic Properties

The annealing effect on the optical and magnetic properties of the GaDyN layers was studied. The PL intensities of yellow and green bands as well as the intra-4f orbital transition of Dy³⁺ ions were found to decrease for the samples annealed at 900 and 1000 °C. It is supposed that the intra-4f orbital transition is related to the broad peak luminescence coming from defects. Increasing the annealing temperature, the magnetization becomes smaller. It is considerable that the number of electrons coming from defects was reduced by the annealing treatments and that the ferromagnetism in GaDyN is attributed as carrier induced ferromagnetism.     

Structural and Magnetic Properties of Nanocrystalline Mg–Co Ferrites

Mg?CCo nano crystalline ferrites having the general formula Mg_1?x Co _x Fe₂O₄ (x=0, 0.05, 0.1, 0.15, 0.2, 0.25) were prepared by the sol?Cgel method. X-ray powder diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR) were carried out to investigate the structural properties of the samples. X-ray powder diffraction patterns indicated the formation of a spinel structure of the prepared compounds. Fourier Transform Infrared (FTIR) spectroscopy of the samples confirmed the XRD results. The crystallite size, lattice parameters and porosity of samples were calculated by XRD data analysis as a function of cobalt concentration. The dielectric constant (?? _r ), dielectric loss tangent (tan???) and ac electrical conductivity (?? _ac) of nanocrystalline Mg?CCo ferrites were investigated as a function of frequency and Co concentration. The frequency dependence of ?? _r , tan??? and ?? _ac is in accordance with the Maxwell?CWagner model. The effect of Co doping on dielectric and electric properties was explained on the basis of cations distribution in the crystal structure. The saturation magnetization M_S, remanent magnetization M_r and coercivity H_C of all samples were explained as a function of cobalt concentration on the basis of Néel??s two-lattice model.     

Annealing Effect on Structural and Magnetic Properties of Cu2MnAl Heusler Alloy Films

Cu₂MnAl Heusler alloy films were grown on MgO (001) substrates by using the ion beam sputtering technique. The films were post-annealed at varying temperatures in order to investigate the influence of annealing on crystal structure and magnetic properties. The structural properties of Cu₂MnAl films have been investigated by using x-ray diffraction (XRD) and magnetic properties have been investigated by both vibrating sample magnetometer (VSM) and ferromagnetic resonance (FMR) techniques. The experimental data indicates that the crystal structure of the films strongly depends on the annealing temperature. When the films were annealed at 200?°C, the saturation magnetization (M _s =250?emu/cm³) achieved its maximum and the coercive field (H _c ??7?Oe) reached its minimum with B2 ordered structure. In addition, FMR results have revealed that the Cu₂MnAl film annealed 200?°C has the highest effective magnetization. The combination of structural and magnetic characterization indicates that the optimum growth temperature is 200?°C for the Cu₂MnAl Heusler alloy films on MgO substrates.     

Effect of Non-magnetic Ions Substitution on Structural,Magnetic and Optical Properties of BiFeO3 Nanoparticles

Non-magnetic Zr⁴⁺ ions substituted BiFeO₃ nanoparticles (BiFe_1?x Zr _x O ₃, x = 0.0, 0.03 and 0.10) were synthesized by sol-gel method. X-ray diffraction and Raman studies indicate the rhombohedral phase for all the samples. The particle size decreases with increasing Zr⁴⁺ concentration and varies in the range 20–50 nm. The absorption spectra show the strong absorption of visible light with optical band gap variation 2.27–2.21 eV for pure and Zr-doped BFO nanoparticles. A large saturation magnetization value of 9.33 emu/g is observed for x = 0.03 sample. The reduction in saturation magnetization for x = 0.10 sample is attributed to the dominant role of an increasing number of non-magnetically active Zr⁴⁺ ions, and the formation of Fe–O–Zr coordination with increasing Zr⁴⁺ ions concentration becomes less magnetic sublattice.     

张力退火感生各向异性对纳米晶合金磁性能的影响

对Fe_74.1Cu₁Nb₃Si₁₅B_6.9(%,原子分数)纳米晶合金进行连续张力退火,研究了张力退火感生各向异性对纳米晶合金磁性能的影响。结果表明,张力退火产生的感生各向异性常数(K_u)与退火张力(σ)满足线性关系。随着退火张力的增大合金在f =5 kHz和H=3 A/m测试点的有效磁导率(μ_e)先增大后减小,且随着磁场和频率的提高有效磁导率(μ_e)的衰减减小。退火张力为67 MPa时有效磁导率(μ_e)在磁场强度H为0~800 A/m和频率f为1 k~3 MHz范围内保持约800,表现出恒导磁特性。同时,合金的单位质量损耗(P_m)随着退火张力的增大而减小,当退火张力为67 MPa时损耗为68 W/kg (测试条件：B_m=300 mT,f =100 kHz),与无张力退火相比下降约67%。同时,通过磁光克尔效应观察到张力退火后合金内部形成垂直于张力方向的180°片形畴,随着退火张力的增大磁畴宽度减小且趋于一致,退火张力为67 MPa时片形畴的宽度约为85 μm。     

Variations of the Effective Magnetostriction with Annealing Conditions for Nanocrystalline Magnetic Alloys

A theoretical model of effective magnetostriction for nanocrystalline magnetic alloys was proposed considering the effects of impurity phases. The dependence of effective magnetostriction on the volume fraction of different components determined by annealing conditions was analyzed. Moreover, the phenomenon that the effective magnetostriction has a valley value which can??t be explained previously was interpreted perfectly by using this model. The results of theoretical analysis are in excellent agreement with existing experimental data.     

Synthesis,Structural, and Magnetic Properties of Nanocrystalline Ti 0.95Co0.05O2-Diluted Magnetic Semiconductors

With a view to investigate the influence of nanometric size on the structural, surface, and magnetic properties of nanocrystalline Ti_0.95Co_0.05O₂-diluted magnetic semiconductors, prepared by a novel simple controllable peroxide-assisted reflux chemical route followed by annealing at different temperatures, a systematic investigation has been undertaken. Structural characterizations such as X-ray diffraction followed by Rietveld refinement, electron diffraction pattern, Fourier transform infrared, Raman scattering, and X-ray photoelectron spectroscopy (XPS) measurements have shown anatase phase formation in nanocrystalline Ti_0.95Co_0.05O₂ without any additional impurity phases. The modified reflux chemical route was effective in obtaining pure phase Ti_0.95Co_0.05O₂ nanoparticles. Surface morphological investigations by using transmission electron microscopy and atomic force microscopy measurements showed the predominant effect of random distribution of nanoparticles on the aggregation behavior and local microstructural changes. The deconvoluted XPS core level Co 2p spectral study manifested the oxidation state of Co as + 2 and is found to be stable with varying particle size and annealing temperature. The ferromagnetic behavior was investigated by vibrating sample magnetometer, magnetic force microscopy, and electron spin resonance measurements. These magnetization studies showed all the samples are ferromagnetic at room temperature without any magnetic clusters. The correlation between structure, surface condition of the nanoparticles and local electronic interactions, and magnetization of the samples was analyzed and explored the origin of ferromagnetism.     

Magnetic and Structural Properties in Co/Cu/Co Sandwiches with Ni and Cr Buffer Layers

1. IntroductionThe gial magnetoresistance (GMR) effect occursin multilayers of ferromagnet ic / nonmagnet ic met almultilayers and sandwiches[1'2]. Many material systems, such as Fe/Crl'], Co/Cut'l, have exhibited theGMR properties. The saturation field in these multilayers is usually very large due to the strong exchange coupling field between the adjacent magneticlayers. Non-coupled type multilayers consisting of twomagnetic components with different coercive forces,and relatively thick …     

Structural, Dielectric, and Magnetic Characterization of Nanocrystalline Ni–Co Ferrites

Spinel ferrites containing Nickel and Cobalt of composition with nominal formula Ni_(1?x)Co_(x)Fe₂O₄ (x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5) prepared by the coprecipitation method are reported. The single phase spinel formation of ferrites was confirmed by X-ray diffraction techniques. The lattice constants (a _th) were calculated based on the ionic radii of the constituents. The calculated lattice constants are smaller than the measured, because for calculations ideal ionic radii are used. The particle size calculated from the Scherrer formula varied within 15 to 33?nm. The dielectric constant and dielectric loss tangent measurement were carried out at room temperature as a function of frequency from 100 Hz to 3 MHz. Both the dielectric constant and dielectric loss tangent increased with increase in cobalt concentration. Ferrimagnetic transition temperature as a function of Co?concentration was measured with the low field ac susceptibility apparatus. The ferrimagnetic transition (T _c ) was observed in the temperature range 573 to 720?K. The T _c decreased with the addition of Co?concentration. The effect of Co?concentration on the magnetic properties was investigated using a vibrating sample magnetometer (VSM). It was found that both magnetic saturation (M _s ) and coercivity (H _c ) increase with Co?concentration.     

Structural,Transport and Optical Properties of Boron-doped Zinc Oxide Nanocrystalline

The paper has reported the structural,transport and optical properties of boron doped zinc oxide(ZnO:B) thin films grown on glass substrate by sol-gel spin coating process.It is observed from the analysis of the X-ray diffraction(XRD) results that the crystalline quality of the films is improved with increasing B concentration.A crystallite size of ～17 nm is obtained for B doped films.A minimum resistivity of 7.9×10-4 Ω.cm is obtained at 0.6 at.% of B concentration in the ZnO:B films.Ionized and intragrain cluster scattering are found to dominate the scattering mechanism in ZnO:B films.Optical interference pattern in transmittance spectra shows good homogeneity with a transparency of ～88% in the visible region.The band gap of the films is increased from 3.24 to 3.35 eV with increasing B concentration.Band gap widening is analyzed in terms of Burstein-Moss shift.The origin of the broad band photoluminescence(PL) spectra is explained in terms of the intragrain cluster scattering.     

退火条件对Sn量子点生长和红外光学性质的影响

首次采用固相外延生长技术在Si(001)表面直接生长Sn量子点,并应用原子力显微镜(AFM)、X射线衍射(XRD)和同步辐射傅里叶红外光谱(FTIR)研究了退火条件对量子点样品的表面形貌、结晶性和红外光学性质的影响.AFM结果表明,随着退火温度的升高和退火时间的延长,量子点的平均尺寸变大,面密度减小.XRD结果显示,外延得到的Sn量子点为四方结构的β-Sn,与衬底的相对取向为Sn(110)//Si(001).由于β-Sn量子点的尺寸仍较大,同步辐射FTIR谱中没有观察到量子点的特征吸收峰.     

Structural and Magnetic Properties of Co diffused CdTe Nanocrystalline Thin Films Deposited by Electron Beam Evaporation

Co diffused cadmium telluride (CdTe) nanocrystalline thin films with different Co content were prepared by depositing CdTe/Co stacked layers on glass substrates at 373 K using electron beam evaporation technique. The effect of Co content on structural, morphological, chemical, Raman, and magnetic studies were carried out. X-ray diffraction (XRD) patterns confirmed that all Co diffused CdTe films are in zinc blende structure. The lattice parameter increased with increase of Co content. The high-resolution scanning electron microscopy (HRSEM) images illustrated the grain size of the films. EDAX data confirmed the presence of Co, Cd, and Te with nearly stoichiometic. Raman spectra revealed peaks corresponding to A1, TO, and LO modes of CdTe and gradual shift in peak position. The increase in intensity confirmed the incorporation of Co into CdTe host lattice. Magnetic measurements showed a clear well-defined room temperature ferromagnetic hysteresis loop.     

Ho,Co共掺杂BiFeO3的磁性及局域结构研究

利用溶胶-凝胶法成功制备Ho-Co共掺杂Bi1-xHoxFe0.95Co0.05O3(x=0.05,0.10,0.15)样品,并对样品的磁性进行了详细研究。研究发现Ho-Co共掺杂的BiFeO3材料的磁性有极大提高;并且随着Ho离子掺杂量的增加,样品的磁性也在不断增强。利用同步辐射实验技术,对样品的局域结构进行了研究,进而分析样品磁性增强的原因。     

Effect of the Electrodeposition Frequency,Wave Form,and Thermal Annealing on Magnetic Properties of [Co0.975Cr0.025]0.99Cu0.01 Nanowire Arrays

Highly ordered [Co _0.975Cr _0.025]_0.99Cu _0.01 nanowire arrays were electrodeposited by conducting alternating current (AC) conditions from sulfate-based electrolyte into nanopores of anodic aluminum oxide (AAO) template with 37 nm pore diameter and the interpore distances of almost 50 nm. Fabricated nanowire arrays were characterized using scanning electron microscopy, alternating gradient force magnetometer, and X-ray diffraction. The results illustrated that varying frequency, wave form, and annealing procedure had influence on magnetic properties of as deposited nanowires. The nanowire arrays electrodeposited at different electrodeposition frequencies show remarkably different magnetic behaviors. Due to increasing of the electrodeposition frequency, the rate of ions for reduction was decreased. The nanowires prepared at various wave form illustrated insignificant impact on magnetic properties. X-ray diffraction patterns display that both as-deposited and annealed nanowire arrays expose the same structure. The raised value of coercivity has been determined in annealed nanowire arrays. Magnetization measurements show that the maximum value of coercivity for [Co _0.975]_0.99Cu _0.01 nanowires is observed at high temperature.