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101.
采用固相反应法制备Sm_(1-x)Ca_xFeO_3(x=0,0.1,0.2,0.3)样品,研究Ca~(2+)掺杂对SmFeO_3介电性能、铁磁性及磁相变温度的影响.X射线衍射图谱分析表明:所有样品的主衍射峰与SmFe03相符合且具有良好的晶体结构.随着x的增加,SmFeO_3样品的晶粒尺寸由原来的0.5μm逐渐增大到2μm.当f=1 kHz时,Sm_(1-x)Ca_xFeO_3(x=0.1,0.2,0.3)样品的ε_r分别是SmFe03的5倍、3倍和2.6倍,而tgσ增大一个数量级.在3T磁场作用下,SmFe03样品的M-H呈线性,随着x的增加,M-H逐渐趋向饱和,Sm_(1-x)Ca_xFeO_3(x=0.1,0.2,0.3)样品的M_r分别是SmFeO_3的20倍、31倍和68倍.X射线光电子能谱分析表明:Fe~(2+)和Fe3+共存于Sm_(1-x)Ca_xFeO_3样品中,Fe~(2+)/Fe~(3+)比例随着x的增加而增大,证明Ca~(2+)掺杂增加了Fe~(2+)的含量,形成Fe~(2+)—O~(2-)—Fe~(3+)超交换作用,增强SmFe03的铁磁特性.测量了Sm_(1-x)Ca_xFeO_3样品在外加磁场为1000 Oe(1 Oe=79.5775 A/m)的M-T变化关系,观测到其自旋重组温度(T_(SR))和尼尔温度(T_N)分别为438 K和687 K,发现SmFe03样品的T_(SR)和T_N均随着x的增加向低温方向移动,当x=0.3时,自旋重组现象消失.这主要是SmFeO_3样品磁结构的稳定性和Fe~(3+)—O~(2-)—Fe~(3+)及Sm~(3+)—O~(2-)—Fe~(3+)超交换三者共同作用的结果. 相似文献
102.
Instanton configurations of (1+1)-dimensions in an antiferromagnetic biaxial-anisotropy-spin-chain are obtained explicitly in the strong anisotropy limit, which interpolate between degenerate equilibrium orientations of the Néel vector along easy axis and are seen to be responsible for quantum tunneling. Macroscopic quantum coherence of the domain walls is demonstrated in terms of the instantons. 相似文献
103.
Feng-jie MA 《Frontiers of Physics》2010,5(2):150
We have studied the electronic and magnetic structures of the ternary iron arsenides AFe2As2 (A = Ba, Ca, or Sr) using the first-principles density functional theory. The ground states of these compounds are in a collinear antiferromagnetic order, resulting from the interplay between the nearest and the next-nearest neighbor superexchange antiferromagnetic interactions bridged by As 4p orbitals. The correction from the spin–orbit interaction to the electronic band structure is given. The pressure can reduce dramatically the magnetic moment and diminish the collinear antiferromagnetic order. Based on the calculations, we propose that the low energy dynamics of these materials can be described effectively by a t−JH−J1−J2-type model [arXiv: 0806.3526v2, 2008]. 相似文献
104.
一维受限反铁磁光子晶体的性质 总被引:4,自引:0,他引:4
采用传输矩阵法计算了一维受限反铁磁光子晶体的带结构和透射比.研究结果表明:除来源于结构周期性的光子带隙外,体系还存在一种频率带隙,与反铁磁材料的共振性质以及受限尺寸有关.适当调节反铁磁各向异性轴的方向和受限尺寸,在反铁磁共振频率处可以出现比大块反铁磁材料的带隙宽约15倍的频率带隙.一定条件下,在大块反铁磁材料带隙的频率区间上,一些电磁波模式是可以在受限光子晶体中传播的.最后分析了几种典型的透射谱,与带结构吻合. 相似文献
105.
A.-L. Barra G. Chouteau A. Stepanov A. Rougier C. Delmas 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(4):551-562
compounds have a layered structure made of alternating Ni-O and Li-O slabs. An amount z of extra divalent Ni ions is always present in the Li-O layers. We show, using high field magnetisation, static and dynamic
susceptibility and high frequency ESR, that the magnetic properties are driven by the z parameter. The compounds can be described as ferromagnetic Ni-O layers, bridged by clusters possessing a net ferromagnetic
moment.
Received: 24 July 1998 / Revised and Accepted: 23 September 1998 相似文献
106.
M. Hagiwara K. Katsumata H. Yamaguchi M. Tokunaga I. Yamada M. Gross P. Goy 《International Journal of Infrared and Millimeter Waves》1999,20(4):617-622
Antiferromagnetic resonance (AFMR) measurements on a well characterized single crystal sample of MnF2 have been performed using various kinds of millimeter and submillimeter sources up to 570 GHz and a superconducting magnet up to 20 T. All the AFMR modes predicted from the theory have been observed. We report a complete frequency-field chart for these AFMR modes. 相似文献
107.
The results of our NMR, EPR and magnetic susceptibility measurements in the paramagnetic state of TlMnCl3 are reported here. The NMR paramagnetic shift of thallium is found to be small but positive. Mn2+ EPR line is exchange narrowed. The susceptibility measurements indicate an antiferromagnetic transition. The heat of crystallographic
phase transition ΔH, in TlMnCl3 has been measured using differential scanning calorimetry. The crystallographic phase transition appears to be first order
and ΔH is unusually low viz. 10 cal mole−1. In the case of KMnF3 ΔH, which is reported here for the first time, is determined to be 2 cal mole−1. 相似文献
108.
A. A. Shteinman 《Russian Chemical Bulletin》1993,42(3):421-423
ESR spectra of 13 bi-, tri- and tetranuclear -oxo complexes of Fe(III) were studied in the solid state and in solution. On the basis of the data obtained, the broad signal observed nearg=2 for all the complexes was interpreted as resulting from thermal populating of paramagnetic excited states.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 470–472, March, 1993. 相似文献
109.
110.
Intramolecular Antiferromagnetism in [Cr2(μ-NH2)3(NH3)6]I3 The magnetism of [Cr2(μ-NH2)3(NH3)6]I3 which consists of binuclear cations with NH2?-bridged face-sharing octahedral coordination polyhedra and a metal-metal separation of 264.9 pm can be explained by antiferromagnetically exchange-coupled CrIII-3d3 pairs. The magnetochemical analysis in the temperature range 5 K – 295 K on the basis of the isotropic Heisenberg model (spin Hamiltonian ? = ?2 J?1 · ?2) leads to the parameter value J = ?98(3) cm?1. Compared to the exchange coupling in corresponding binuclear chromium compounds with OH? bridges and identical metal-metal separation the strength of the coupling is significantly enhanced (JNH2/JOH ≈? 1.6). 相似文献