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131.
Electronic and magnetic properties of BiFeO_3 with intrinsic defects:First-principles prediction 下载免费PDF全文
The electronic structure, magnetism, and dielectric functions of BiFeO3 with intrinsic vacancies, including Bi-, Fe-, and O-vacancies (denoted as VFe, VBi, and Vo, respectively) are investigated using the first-principles density functional theory plus U calculations. It is revealed that the structural distortions associated with those vacancies impose significant influences on the total density of state and magnetic behaviors. The existence of VBi favors the excitation of the O2p state into the band gap at 0.4 eV, while the O2p and Fe3d orbitals are co-excited into the band gap around 0.45 eV in VFe- Consequently, a giant net magnetic moment of 1.96 P-B is generated in VFe, and a relatively small moment of 0.13 P-B is induced in VBi, whereas Vo seems magnetically inactive. The giant magnetic moment generated in VFe originates from the suppression of the spatially modulated antiferromagnetic spin structure. Furthermore, VFe and VBi have strong influences on dielectric function, and induce some strong peaks to occur in the lower energy level. In contrast, VO has a small effect. 相似文献
132.
We report two ultra-stable laser systems automatically frequency-stabilized to two high-finesse optical cavities. By employing analog-digital hybrid proportional integral derivative(PID) controllers, we keep the merits of wide servo bandwidth and servo accuracy by using analog circuits for the PID controller, and, at the same time, we realize automatic laser frequency locking by introducing digital logic into the PID controller. The lasers can be automatically frequency-stabilized to their refer... 相似文献
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134.
Monolayer MnTe2 stabilized as 1T structure has been theoretically predicted to be a two-dimensional (2D) ferromagnetic metal and can be tuned via strain engineering. There is no naturally van der Waals (vdW) layered MnTe2 bulk, leaving mechanical exfoliation impossible to prepare monolayer MnTe2. Herein, by means of molecular beam epitaxy (MBE), we successfully prepared monolayer hexagonal MnTe2 on Si(111) under Te rich condition. Sharp reflection high-energy electron diffraction (RHEED) and low-energy electron diffraction (LEED) patterns suggest the monolayer is atomically flat without surface reconstruction. The valence state of Mn4+ and the atom ratio of ([Te]:[Mn]) further confirm the MnTe2 compound. Scanning tunneling spectroscopy (STS) shows the hexagonal MnTe2 monolayer is a semiconductor with a large bandgap of ~2.78 eV. The valence-band maximum (VBM) locates at the Γ point, as illustrated by angle-resolved photoemission spectroscopy (ARPES), below which three hole-type bands with parabolic dispersion can be identified. The successful synthesis of monolayer MnTe2 film provides a new platform to investigate the 2D magnetism. 相似文献
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136.
Through a mapping relation between the triple sine-Gordon and Ф5 model, we discuss the equation in detail. A series of solitary wave solutions for the triple sine-Gordon equation is obtained by the existing ones of the Ф5 model. Some detailed solitary wave solutions are given for some special coefficients which have significance in physics. 相似文献
137.
When R satisfies (strong unit) 1-stable range and M is a R-R-bimodule, theauthors calculate that K1(R ∞ M) ≌ U(R ∞ M)/L(R ∞ M). As applications, the authors also calculate some Whitehead groups for exchange rings with artinian primitive factors.Key words Whitehead group, module extension, (strong unit) 1-stable range 相似文献
138.
建筑涂料用苯丙乳液的研制 总被引:11,自引:0,他引:11
本文采用自由基乳液聚合方法,通过苯乙烯,丙烯酸丁酯和丙烯酸三元共聚反应,合成了建筑涂料用的苯丙乳液。通过大量的实验确定了反应配方及加料方式,并详细讨论了各组分及反应条件对聚合反应和产品性能的影响。 相似文献
139.
对H2D+通过碳膜后的产物H+和D+的获取与测量,研究了H2D+的同位素效应以及离子穿过固体的尾流效应.H2D+的化学结构得到测定.H2D+的非对称结构得到确认.测量结果与通过其它方式对H2D+的研究结果相一致. 相似文献
140.
本文将介绍抛物线的一种参数方程的一些应用。为此,先说明抛物线参数方程中参数的意义。为方便起见,我们将抛物线的标准方程写成: y~2=4ax 这里a为抛物线的焦点到它的准线的距离的一半,所以a>0。设抛物线y~2=4ax的这种参数方程为: 相似文献