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1.
采用固相反应法制备了不同烧结温度(950~1 180 ℃)、烧结时间、烧结次数共7种工艺的Sr3YCo4O10.5+δ多晶块材,通过热分析、XRD、SEM确定了有序化相变和最佳烧结工艺(1 180 ℃/24 h+1 180 ℃/24 h),并研究了多晶的电磁性能。结果表明,964 ℃完全晶化的四方相Sr3YCo4O10.5在1 042 ℃吸氧(δ)完成有序化,生成Sr3YCo4O10.5+δ,而1 100 ℃和1 180 ℃烧结的样品均出现(103)、(215)超结构峰,验证了其结构的有序性。块材均呈半导体电输运行为,二次烧结晶格完整性提高,晶粒长大,300 K时电阻率仅为0.06 Ω·cm,居里温度(Tc)~335 K,零场冷曲线(ZFC)上的Hopkinson峰源于低温时被冻结的磁矩随温度升高转向磁场方向,磁化强度在298 K达到最大,随后受热扰动的影响减小。室温铁磁性源于有序结构导致的中自旋或高自旋态Co3+的eg轨道有序。 相似文献
2.
The realization of ferromagnetic ordering of two-dimensional (2D) carbon material graphdiyne (GDY) has attracted great attention due to its promising application in spin semiconductor devices. However, the absence of localized spins makes the pristine GDY intrinsically nonferromagnetic. Herein, we report the realization of robust room-temperature (RT) ferromagnetism (FM) with Curie temperature (TC) up to 325 K for GDY Nanosheets (GDYNs) by supercritical CO2 (SC CO2). Experimental and theoretical calculations reveal that the new chemical bond of C−O−Si can be formed because of the unique effect of SC CO2, which help to enhance the charge transfer and generates long-range ferromagnetic order. The RT saturation magnetization (MS) reaches 1.125 emu/g, which is much higher than that of carbon-based materials reported up to now. Meanwhile, by changing the conditions of SC CO2 such as pressure, ferromagnetic responses can be manipulated, which is great for potential spintronics applications of GDY. 相似文献
3.
The rutile phase Sn0.99-xMnxCr0.01O2 (x = 0.00, 0.01, 0.03, 0.05 and 0.07) nanoparticles were synthesized by facile chemical co-precipitation method using poly ethylene glycol (PEG) as a capping agent. The samples were characterized by EDAX to confirm the expected stoichiometry. The X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy analyses of these samples showed the formation of impurity free crystals with a single phase rutile type tetragonal crystal structure as that of (P42/mnm) of SnO2. Optical absorption spectra and corresponding Tauc's plots showed a redshift of the absorption edge in SnO2 after being co-doped with Cr and Mn. The samples were examined for its magnetic property using vibrating sample magnetometer which indicated that transition of magnetic signals from ferromagnetic to the paramagnetic nature with inclusion of Mn content in SnO2: Cr host matrix. The observed magnetic behavior is well supported with the bound magnetic polarons (BMPs) model. 相似文献
4.
Specimens of iron-doped indium oxide (In1-xFex)2O3 with x?=?0.015, 0.03, 0.045 and 0.06, amalgamated through a traditional solid-state reaction method followed by H2/air sintering, were characterised using an X-ray diffractometer (XRD), a vibrating sample magnetometer (VSM), and a scanning electron microscope (SEM) to investigate their structural, magnetic and morphological properties respectively. According to XRD plots, all the specimens exhibit cubic bixbyite structures along with ancillary phases. Magnetic assessment showed that In2O3 has a negative susceptibility, exhibiting diamagnetic behaviour at room temperature. The doping of Fe ions induces ferromagnetic (FM) ordering, which is enhanced with increasing doping content. The strength of the magnetisation increases when the specimens are exposed to H2 but is reduced on further air sintering. A bound magnetic polaron (BMP) model is successfully fitted to the observed FM data involving localised carriers and magnetic cations. A multivariate assessment viz. a hierarchical cluster analysis (HCA) was used to corroborate and strengthen the experimental determined magnetic properties. A homogeneous particle distribution was observed in all SEM micrographs and is validated through MATLAB-based simulation by applying a watershed segmentation algorithm. Surface plots also confirm the change in magnetic properties with increase in doping concentration. 相似文献
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6.
Dr. Carmen J. Calzado 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(4):1254-1261
This paper reports a theoretical analysis of the electronic structure and magnetic properties of a tetranuclear CuII complex, [Cu4(HL)4], which has a 4+2 cubane‐like structure (H3L=N,N′‐(2‐hydroxypropane‐1,3‐diyl)bis(acetylacetoneimine)). These theoretical calculations indicate a quintet (S=2) ground state; the energy‐level distribution of the magnetic states confirm Heisenberg behaviour and correspond to an S4 spin–spin interaction model. The dominant interaction is the ferromagnetic coupling between the pseudo‐dimeric units (J1=22.2 cm?1), whilst a weak and ferromagnetic interaction is found within the pseudo‐dimeric units (J2=1.4 cm?1). The amplitude and sign of these interactions are consistent with the structure and arrangement of the magnetic Cu 3d orbitals; they accurately simulate the thermal dependence of magnetic susceptibility, but do not agree with the reported J values (J1=38.4 cm?1, J2=?18.0 cm?1) that result from the experimental fitting. This result is not an isolated case; many other polynuclear systems, in particular 4+2 CuII cubanes, have been reported in which the fitted magnetic terms are not consistent with the geometrical features of the system. In this context, theoretical evaluation can be considered as a valuable tool in the interpretation of the macroscopic behaviour, thus providing clues for a rational and directed design of new materials with specific properties. 相似文献
7.
氧化锌(ZnO) 纳米材料因其在UV 激光器、发光二极管、太阳能电池、稀磁半导体、生物荧光标示、靶向药物等领域中的广泛应用而成为最热门的研究课题之一. 调节和优化ZnO 纳米结构的性质是ZnO 的实际应用迫切所需. 在此, 通过发展聚乙烯吡咯烷酮导向结晶法、微波加热强制水解法、表面活性剂后处理法, 成功地制备出了尺寸、表面电荷或成分可调的球、半球、棒、管、T 型管、三脚架、片、齿轮、两层、多层、带盖罐子、碗等一系列ZnO 纳米结构. 通过简单地改变ZnO 纳米粒子的尺寸、形貌和表面电荷或成分, 有效地调控ZnO 本身的发光强度和位置, 并近90 倍地增强了荧光素染料的荧光强度; 诱使了强度可调的室温铁磁性; 实现了对ZnO纳米颗粒的细胞毒性的系统性调控. 相似文献
8.
9.
利用直流磁控溅射技术在玻璃衬底上沉积了TiO2薄膜,并对其进行了Co离子注入,最后在真空中500 ℃退火50 min,得到系列薄膜样品. 利用剥离-分散方法制备了薄膜的透射电镜样品,并用扫描电镜(SEM)、X射线能量散射谱(EDX)和高分辨透射电镜(HRTEM)对样品做了近似原位观察,研究了薄膜样品中不同Co离子注入深度的成分分布和显微结构. 结果表明,薄膜呈锐钛矿结构,Co元素主要分布在薄膜表层,Co离子的注入使TiO2薄膜的晶粒被部分破坏,并形成CoO,而5
关键词:
2薄膜')" href="#">Co注入TiO2薄膜
电镜原位观察
室温铁磁性 相似文献
10.
L.B. Drissi A. Benyoussef E.H. Saidi M. Bousmina 《Journal of magnetism and magnetic materials》2011,323(23):3001-3006
The magnetic properties of Mn-doped ZnO semiconductor have been investigated using the Monte Carlo method within the Ising model. The temperature dependences of the spontaneous magnetization, specific heat and magnetic susceptibility have been constructed for different concentrations of magnetic dopant Mn and different carrier concentrations. The exact values of Mn concentration and carrier concentration at which high temperature transition occurs are determined. An alternative for the explanation of some controversies concerning the existence and the nature of magnetism in Mn diluted in ZnO systems is given. Other features are also studied. 相似文献