Hydrothermal preparation and characterization of Cd0.9Mn0.1S nanorods

Cd_0.9Mn_0.1S semiconductor nanorods were successfully prepared by the hydrothermal reaction of CdCl₂·2.5H₂O and MnCl₂·5H₂O with (NH₄)₂S in aqueous solution. Atomic absorption spectrometry (AAS) and energy dispersive spectroscopy (EDS) were used to determine the Mn contents of these complex nanorods. The samples were characterized by scanning electron microscopy (SEM-EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis absorption spectra, photoluminescence (PL) and compared with the undoped CdS nanorods. The results showed that nanostructured multiplex compounds with high aspect ratio were obtained via hydrothermal method. The products showed almost totally rod-like morphology with approximately identical diameter about 20 nm and the maximal length up to 200 nm.     

Effect of indium doping on photoelectrochemical properties of Cd0.9Zn0.1Se photosensitive films

Indium doped Cd_0.9Zn_0.1Se films have been synthesized by chemical bath deposition method. The deposited films act as photoanode in photoelectrochemical (PEC) cells. The varying concentration of indium from 0.01 to 1.0 mol% was used. The film thickness increases from 0.72 to 0.80 μm as doping concentration increases up to 0.1 mol%, thereafter it decreases. The cell configuration is n-Cd_0.9Zn_0.1Se:In|NaOH (1 M)+S (1 M)+Na₂S (1 M)|C_(graphite). The various performance parameters were examined with respect to doping concentration of indium. It is found that fill factor and efficiency is maximum for 0.1 mol% indium photosensitive films. This is due to low resistance, high flat band potential, maximum open circuit voltage as well as maximum short-circuit current. The barrier height was examined from the temperature dependence of the reverse saturation current. The lighted ideality factor was found to be minimum for 0.1 mol% indium photosensitive films. A cell utilizing doping photosensitive films showed a wider spectral response. The utility of this work is in improving efficiency of the PEC cell.     

Magnetoresistance near the metal-insulator transition of Cd0.99Mn0.01Se

At 0.5 ≤ T ≤ 4.2 K samples of Cd_0.99Mn_0.01Se which are near the metal-insulator transition exhibit a large positive magnetoresistance (MR) in fields H ∽ 10 k0e. The effect is accompanied by an increase in the Hall coefficient and a decrease in the Hall mobility. At the lowest temperatures and for fields well above 10 k0e a small negative MR is observed. The positive MR is tentatively attributed to an increase in the screening radius r_s, which leads to enhanced Coulomb-potential fluctuations.     

Cd0.9Zn0.1Te晶体的Cd气氛扩散热处理研究

将生长得到的Cd_0.9Zn_0.1Te晶体在Cd气氛下及不同的温度条件下进行了退火处理. 借助已建立的退火处理过程中Cd_1-xZn_xTe晶体材料电阻率及导电类型变化和扩散杂质的扩散系数之间关系的模型，结合实验数据，获得了1073K，973K和873K下Cd在Cd_0.9Zn_0.1Te晶体中的扩散系数，并估算了其激活能. 通过使用获得的扩散系数，研究了在不同温度及饱和Cd气氛下，退火时间对Cd_0.9Zn_0.1Te晶体电阻率分布及导电类型等的变化的影响.     

Giant magnetoresistance in Y0.9La0.1Mn6Sn6 compound

Magnetic transitions and magnetoresistance effect of the HfFe_6Ge_6-type Y_{0.9}La_{0.1}Mn_6Sn_6 compound have been investigated in the temperature range of 5－380K. The sample displays antiferromagnetic behaviour in the whole temperature range below Néel temperature T_N=309K. The metamagnetic transition from antiferromagnetism to ferromagnetism can be induced by an applied field. The metamagnetic transition field decreases monotonically from 2T at 5K to 0.4T at 300K. The giant magnetoresistance effect is observed with the metamagnetic behaviour, such as -10.4% at 245K under a field of 5T.     

Fe NMR, magnetization and X-ray study of Cd0.1Cu0.9Fe2O4 ferrite

⁵⁷Fe NMR spin-echo spectra, static magnetization and X-ray diffraction measurements for Cd_0.1Cu_0.9Fe₂O₄ ferrite taken in a wide range of temperatures are presented. The X-ray studies show that above 100 K the structure is cubic. The temperature dependence of the effective magnetic field acting on ⁵⁷Fe nuclei at non-equivalent tetrahedral and octahedral sites has been determined. Different thermal behaviour of the magnetic field at both sublattices and of the specific macroscopic magnetization have been found. Magnetization measurements imply that cadmium substitution does not affect the ferric ion distribution between the sublattices of the ferrite.     

单相Bi0.9Ba0.1Fe0.85Mn0.15O3陶瓷中的多铁性

溶胶-凝胶法制备了Bi_0.9Ba_0.1Fe_0.85Mn_0.15O₃陶瓷样品,XRD分析显示其为单相菱方钙钛矿结构,明显的磁滞回线和电滞回线说明其在室温具有弱铁磁性和铁电性,介电常数随外磁场的变化显示双掺样品具有更大的磁容效应. 关键词： 溶胶-凝胶法 多铁材料 磁容效应     

Magnetic pair making and breaking effect of Ru in La0.7Sr0.3Mn0.9Ru0.1O3 and La0.5Sr0.5Co0.9Ru0.1O3

The substitutional effect of Ru on the magnetic and transport properties of double exchange ferromagnets, La_0.7Sr_0.3MnO₃ and La_0.5Sr_0.5CoO₃ has been investigated. It is found that substitution of 10% Ru at the Mn site of La_0.7Sr_0.3MnO₃ decreases the Curie temperature by 20 K than that of the parent compound. However, a large decrease in the Curie temperature, ΔT_c80 K and the system undergoes a transition from metallic state to insulating state is observed when 10% Ru is doped in La_0.5Sr_0.5CoO₃. The marginal effect of Ru in the Mn–O–Mn sublattice in comparison to the Co–O–Co sublattice could be due to the magnetic exchange interaction between Mn and Ru by virtue of the fact that Ru exhibits variable valence states, Ru⁺⁴/Ru⁺⁵. The e_g and t_2g parentage of Ru⁺⁵ is similar to Mn⁺⁴ and therefore, Ru⁺⁵ ion appears to participate in the double exchange mediated ferromagnetic (FM) interaction. On the other hand, Ruthenium (IV) ion disrupts an intermediate spin state of cobalt (Co⁺³: t_2g⁵e_g¹), forcing a double exchange FM state to anti-FM state.     

Spectral photoconductivity in high manganese concentration Cd0.27Mn0.73Te

Photoconductivity results are reported for samples of Cd_0.27Mn_0.73Te. They are compared to the absorption ones, in the range 1.8–3 eV. The frequency response study allows us to present a model consistent with both phenomena: the minimum observed in the photoconductivity spectrum is attributed to a competition between the intrinsic absorption and the intra- manganese transitions. In addition the transitions between 6_A1?4_T1 and 6_A2?4_T2 could be separated; they are unresolved in the absorption spectrum giving a wide bump.     

Magnetic and electrical transport properties in the self-doped manganite La0.9Mn0.9M0.1O3 (M=Mn,Zn and Ti)

The magnetic and electrical transport properties of La_0.9Mn_0.9M_0.1O₃ (M=Mn, Zn and Ti) were investigated. The temperature and magnetic field dependence of electrical resistivity (ρ) and dc magnetization were studied. All the compounds are found in rhombohedral structure. The excess oxygen in all three compounds was detected through iodometric titration. A modification in resistivity is observed when M=Mn is replaced by M=Zn and Ti. The high temperature resistivity above T_C follow variable range hopping model for both Zn and Ti compounds. For Zn doping, the observation of large field-cool effect and decrease in resistivity at room temperature and is assumed to be due to the implant of Mn⁴⁺ in Mn³⁺ matrix, which favor Mn³⁺/Mn⁴⁺ double exchange. The ferromagnetic behavior below T_C for the compound with M=Ti is correlated to the excess oxygen in it, which implants Mn⁴⁺ and thus incorporates ferromagnetic interactions. The substitutions lead to a reduction of T_c and magnetization.     

Cd_(0.96)Zn_(0.04)S/Cd_(0.97)Mn_(0.03)S/Cd_(0.96)Zn_(0.04)S多层纳米线中s-d交换作用的研究

以氧化铝纳米孔为模板,采用直流电化学沉积的方法制备了Cd_(0.96)Zn_(0.04)S/Cd_(0.97)Mn_(0.03)S/Cd_(0.96)Zn_(0.04)S量子阱纳米线阵列,并系统研究了该纳米线阵列在不同温度和不同磁场下的电学输运特性.随着外磁场的变化,样品表现出共振传输特性.通过量子阱理论对实验现象进行了分析,直接得到了稀磁层Cd_(0.97)Mn_(0.03)S中s-d交换作用常数N_0α的定量结果.研究发现该交换作用常数随温度具有e~(-1/T)的变化趋势.     

Anisotropic exchange interaction in CdTe/Cd0.75Mn0.25Te quantum wires

We observed anisotropic large peak-energy shift of photoluminescence (PL) from CdTe/Cd_0.75Mn_0.25Te quantum wires (QWRs). The large PL-peak-energy shift is caused by the exchange interaction between excitons in the non-magnetic QWR and Mn ions in the DMS barrier. The exchange interaction is enhanced when magnetic field is perpendicular to the QWR.     

Influence of Dy addition on the magnetocaloric effect of La0.67Ca0.33Mn0.9V0.1O3 ceramics

The influence of partial substitution of La by Dy on the magnetocaloric response of (La_1−xDy_x)_0.67Ca_0.33Mn_0.9V_0.1O₃, where x=0.03, 0.15 and 0.25 is studied. Rietveld refinement of X-ray diffraction pattern using GSAS method shows that the compounds adopt the orthorhombic structure with Pnma space group. The systematic change in lattice parameters and magnetic phase transition indicates the substitution effect of Dy. From the magnetization isotherms at different temperatures, magnetic entropy change close to their respective transition temperatures (T_C) has been evaluated. The maximum value of entropy change near T_C is found to be about 4.8 J/kg K at 187.5 K for LCMVDy_0.03, 2.45 J/kg K at 107.5 K for LCMVDy_0.15 and 2.15 J/kg K at 92.5 K for LCMVDy_0.25 at 4 T. Dy addition produces a reduction in T_C and in magnitude of the magnetic entropy change. Even though the entropy change decreases with increasing Dy substitution the refrigerant temperature range, ΔT, is found to be 10 K for LCMVDy_0.03, 31 K for LCMVDy_0.15 and 35 K for LCMVDy_0.25 compounds [90%] at 4 T. The field dependence of the magnetic entropy change is also analyzed showing the power law dependence, ΔS_M∞Hⁿ where n=0.75(2) for LCMVDy_0.03, n=0.80(4) for LCMVDy_0.15 and n=0.92(8) for LCMVDy_0.25 compounds at their respective transition temperatures. The relative cooling power and its field dependance are also analyzed.     

Electron IMFPs in bulk Cd0.88Mn0.12Te crystals determined by EPES

The inelastic mean free path (IMFP) of electrons is a basic parameter for surface-sensitive electron spectroscopies (AES, XPS, EELS) in quantitative analyses.Cd_1−xMn_xTe mixed crystals are currently of great interest due to their magnetic and magneto-optical properties. Since information on electron transport processes in these semimagnetic compounds is scarce, their systematic studies are highly desirable.In the present work, the IMFPs in Cd_0.88Mn_0.12Te (1 1 0) crystal samples were obtained from EPES with use of the Ni standard in the electron energy range 500-2000 eV. In addition, we also explored the effect of bulk Mn content in the determination of the IMFP. Relative EPES measurements were carried out using the MICROLAB 350 spectrometer. The sample surface was sputter cleaned and amorphized by Ar⁺ ions. Surface composition of the samples was monitored in situ by XPS and AES. The measured IMFPs were uncorrected for surface excitations and compared with those predicted from the TPP-2M and G-1 formulae. Also, the values of the IMFPs determined here were compared with those evaluated from the expression of Sekine et al. However, accuracy of this expression is rather poor except the case of pure CdTe (x = 0). In general, good agreement was found between the measured IMFPs in Cd_0.88Mn_0.12Te and the corresponding predicted IMFPs. The root-mean-square deviation from IMFP values predicted from the TPP-2M formula was 1.2 Å. The mean percentage deviation from the TPP-2M IMFPs was 9.3%.     

Spin glass like behavior in Cd0.42Mn0.58In2S4

The magnetic behavior of the diluted magnetic semiconductor Cd_0.42Mn_0.58In₂S₄ has been study by dc magnetization and ac susceptibility experiments. Zero field cooled and field cooled measurements reveal irreversibility below T_irr=2.60±0.15 K. Ac susceptibility data, performed as a function of the temperature and the frequency, confirm the spin-glass like behavior of the material with T_f=2.75±0.15 K. High temperature susceptibility data follow a typical Curie-Weiss law with θ=−74±1 K which suggests predominant antiferromagnetic interactions. The randomness of the magnetic ions, necessary to explain the magnetic behavior of the material, has been determined by X-ray powder diffraction experiments.     

Enhancement of the magnetostrictive properties of Co0.9Mn0.1Fe2O4 synthesized by using the precursor preparation technique

Co_1−xMn_xFe₂O₄ has been prepared by calcining hydrotalcite-like precursors for the first time. The crystallization behaviors and magnetoelastic properties of the samples have been investigated. The experimental results show that precursor preparation technique is superior compared to the traditional ceramic method. By adopting hydrotalcite-like precursor preparation technique, a fine and more uniform microstructure can be developed. An obvious enhancement of magnetostriction from 95 to 122 ppm and saturation magnetization from 66 to 78 emu/g has been obtained in Co_0.9Mn_0.1Fe₂O₄ composite under lower magnetic filed. This is propitious to apply to sensors and actuators.     

Electrostatic spray deposition of Gd0.1Ce0.9O1.95 and La0.9Sr0.1Ga0.8Mg0.2O2.87 thin films

The deposition of gadolinia-doped ceria (CGO, Gd_0.1Ce_0.9O_1.95) and LaGaO₃-based perovskite oxides (LSGM, La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.87) thin films on a stainless steel substrate was studied using the electrostatic spray deposition (EDS) technique. The effect of process conditions, such as deposition temperature, deposition time and liquid flow rate, on the surface morphology and microstructure of thin films was examined with scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). The deposited CGO films with a highly porous and three-dimensional interconnected structure were obtained at a liquid flow rate of 0.5 ml/h, a deposition temperature of 503 K and a deposition time ranging from 0.5 to 1 h. On the other hand, the deposited LSGM thin films with porous microstructure were also obtained at the deposition time of 1 h, the deposition temperature of 533 K and the liquid flow rate of 0.5 ml/h. The deposited CGO and LSGM thin films were amorphous at the used deposition temperature. Subsequently, the samples were annealed at 1173 K for 2 h and the desired crystal structures were obtained. The chemical analysis of the thin films was investigated by energy dispersive X-ray (EDX) analysis. The observed chemical compositions of the samples were in a fair agreement with those of the starting solutions.     

Jahn-Teller transition and electron-phonon interaction in Cr-doped manganites Sr0.9Ce0.1Mn1−yCryO3

Cr-doped manganites Sr_0.9Ce_0.1Mn_1−yCr_yO₃ (y=0, 0.05, and 0.10) have been systematically investigated by X-ray, magnetic, transport, and elastic properties measurements. For parent compound Sr_0.9Ce_0.1MnO₃, it undergoes a metal-insulator (M-I) transition at 318 K, which is suggested to originate from a first-order structural transition accompanied by Jahn-Teller (JT) transition. With increasing Cr doping content, the JT transition temperature decreases. The Cr doping suppresses the antiferromagnetic (AFM) state and makes the system spin-glass (SG) behavior at low temperatures. In the vicinity of JT transition temperatures, the softening of Young's modulus originating from the coupling of the orbital (quadrupolar) moment of the e_g orbital of Mn³⁺ ion to the elastic strain has been observed. The anomalous Young's modulus properties imply the electron-phonon coupling due to the JT effect may play an important role in the system.     

稀磁半导体Hg0.89Mn0.11Te磁化强度及磁化率的研究

利用MPMS-7(magnetic property measurement system)型超导量子磁强计对垂直布里奇曼法生长的Hg_0.89Mn_0.11Te晶片磁化强度变化规律进行了测量.试验采用了两种不同的外场和冷却条件.首先在5 K恒温下，-5200到5200 kA/m范围内改变磁场强度进行了测定.然后维持800 kA/m恒定磁场，分别在有场冷却和无场冷却条件下，从5到300 K范围内改变温度，研究了变温条件下的磁化特性.并采用分子场近似模型，用类布里渊函数，最小二乘法对磁化强度随磁场强度变化的实验结果进行拟合和分析，结果表明，Mn²⁺离子之间存在反铁磁相互作用.磁化率和温度关系分析表明：在测试范围内Hg_0.89Mn_0.11Te是单一的顺磁相，在高温区磁化率和温度服从居里-万斯定律，呈线性关系，低于40 K时，磁化率和温度的关系偏离居里-万斯定律，表现出顺磁增强现象. 关键词： 0.89Mn_0.11Te')" href="#">Hg_0.89Mn_0.11Te 磁化强度 磁化率 类布里渊函数     

La0.9Sr0.1MnO3薄膜中电流效应研究

用直流磁控溅射法在(100)LaAlO₃衬底上制备了La_0.9Sr_0.1MnO₃薄膜.经退火处理后薄膜的原子力显微镜形貌观测和X射线衍射分析显示具有比较好的质量.电阻率-温度关系表明La_0.9Sr_0.1MnO₃薄膜在281 K处发生金属绝缘体转变.电流在0.01—4 mA范围内，薄膜的峰值电阻率随电流增大而减小，在4 mA下获得了30.5%的峰值电阻率变 关键词： 掺杂锰氧化合物 0.9Sr_0.1MnO₃薄膜')" href="#">La_0.9Sr_0.1MnO₃薄膜 电流诱导效应 相分离理论