共查询到19条相似文献,搜索用时 203 毫秒
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通过求解磁性d波超导中的能隙与磁交换能的自恰方程,利用推广的Blonder-Tinkham-Klapwijk 理论研究磁性半导体/磁性d波超导结中自旋极化准粒子输运系数与微分电导. 计算表明: 1) 磁性d波超导结中的磁交换能h0可导致零偏压电导峰与能隙电导峰劈裂,劈裂的宽度为2h0;2) 磁性半导体中的磁交换能hFS可使零偏压电导峰劈裂的峰值变低. 而由能隙电导峰劈裂的两个子峰,当两种磁性材料的磁
关键词:
磁性半导体
磁性d波超导体
自旋极化输运 相似文献
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用全势线性缀加平面波方法,考虑局域自旋密度近似研究虚晶掺杂MgCNi3的超导电性和磁性.计算了自旋极化能带结构、体弹性模量和它对压力的导数、原子磁矩m及其变化率.计算结果表明,对于电子掺杂的Mg1-xAlxCNi3(0≤x≤0.5),超导电性和磁涨落随掺杂量的增加逐渐减小.空穴掺杂的Mg1-xNaxCNi3,在x=0.12处出现铁磁相变,超导电性消失.在MgCNi3少量空穴掺杂区域(0≤x<0.12),表现为超导与磁涨落共存的不稳定状态.
关键词:
超导电性
能带结构
态密度
磁性 相似文献
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本文考虑自旋轨道耦合作用的情况下,采用紧束缚近似螺旋对称模型计算了单壁碳纳米管的电子能带结构.研究发现:对于Armchair型单壁碳纳米管,自旋轨道耦合作用和弯曲效应共同导致了费米面Dirac点附近电子能带结构的能隙;对于Zigzag型和手性单壁碳纳米管,自旋轨道耦合作用使得电子最高占据态和最低未占据态产生能级劈裂,能级劈裂的大小不但与碳纳米管的直径和手性角密切相关,而且相对于费米面是不对称的;根据指数(n,m)可以将Zigzag型和手性单壁碳纳米管分为金属性碳纳米管(ν=0)
关键词:
单壁碳纳米管
自旋轨道耦合
紧束缚近似螺旋对称模型 相似文献
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采用基于密度泛函理论的第一性原理方法,计算了Sb系half-Heusler合金XYSb(X=Ni,Pd,Pt;Y=Mn,Cr)的晶体结构、磁性及电子结构.计算结果表明,在平衡晶格常数下,合金NiMnSb为半金属,其他为金属.合金的总磁矩主要由Y元素自旋磁距贡献,随着元素X原子序数减小,费米能级移向自旋向下能带导带底;压缩使费米能级上移,远离Sb原子p能带,PtMnSb,PdMnSb与NiCrSb在压应力下可实现金属—磁性半金属转变.
关键词:
第一性原理
磁性
电子结构
金属—磁性半金属转变 相似文献
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《Physics letters. A》1997,224(3):203-208
A quasi-one-dimensional alternating-spin Heisenberg model is used to describe the charge-transfer organic ferromagnet, which is studied by the Green's function method. The magnetic properties of the charge-transfer organic ferromagnet in different temperature regions are obtained. A formula for the critical temperature Tc is obtained and is found to be related to the spin of donors, to the intrachain exchange interaction, and to the spatial anisotropy parameter. This conclusion can explain Tc of the organic ferromagnet. The spatial anisotropy parameter of the organic ferromagnet [FeCp21][TCNE] we obtained is consistent with the estimated value of Narayan et al. The Curie-Weiss temperature Θ for the organic ferromagnet [CrCp21][TCNE] we obtained is Θ = 15.6 K which is near the experimental result of θ = 22±1 K. 相似文献
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S. R. Boidedaev 《Technical Physics》2010,55(10):1543-1546
The field and orientational dependences of magnetic linear birefringence in α-Fe2O3: Ga single crystals are investigated. The experimental results make it possible to refine and specify the structure and reveal
the features of technical magnetization of the modulated magnetic phase of this weak ferromagnet. It is shown that the model
of the modulated magnetic structure used in this study adequately describes the experimental situation. 相似文献
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Takeshi Murata Tomoyuki TeraiTakashi Fukuda Tomoyuki Kakeshita 《Journal of magnetism and magnetic materials》2006
We have examined magnetizations as a function of temperature and magnetic field in layered perovskite manganites La2−2xSr1+2xMn2O7 single crystals (x=0.313, 0.315, 0.318, 0.320 and 0.350) in order to determine the phase boundary between two ferromagnets (one is an uniaxial ferromagnet whose easy axis is parallel to the c-axis and the other is a planar ferromagnet whose easy axis is within the ab-plane) and following results are obtained: (i) all the present manganites exhibit magnetic transitions from a ferromagnet to a paramagnet at 76, 107, 116, 120 and 125 K for x=0.313, 0.315, 0.318, 0.320 and 0.350, respectively; (ii) for x=0.318, 0.320 and 0.350, the magnetic structure is a planar ferromagnet below Curie temperature; (iii) for x=0.313 and 0.315, the magnetic structure changes from an uniaxial to a planar ferromagnet at 66 and 85 K, respectively. From the results described above we have constructed the magnetic phase diagram of layered perovskite manganite La2−2xSr1+2xMn2O7 (0.313?x?0.350). 相似文献
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V. V. Novikov 《Physics of the Solid State》2009,51(10):2101-2104
The change in the magnetization of a ferromagnet due to disordering in the system of atomic magnetic moments with increasing
temperature is put in correspondence with the change in the entropy of the magnetic subsystem. A relationship is obtained
for calculating the magnetic component of the heat capacity of the ferromagnet, which satisfactorily describes the temperature
dependence of the heat capacity for Fe, Co, TbB2, and DyB2 at low temperatures. 相似文献
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The magneto-optical method is used to investigate magnetization and low-frequency magnetic susceptibility curves of the FeBO3 single crystal doped with diamagnetic Mg ions. It is demonstrated that substitution of a fraction of Fe ions by the Mg ions
in the structure of this easy-plane weak ferromagnet causes a significant intraplane magnetocrystalline anisotropy at low
temperatures as well as different forms of magnetic hysteresis loops and field dependences of the magnetic susceptibility
recorded for different orientations of the external magnetic field relative to the basal crystal plane. The established special
features of the FeBO3:Mg magnetic properties are explained by the transition of the magnetic crystal from the uniform to spatially modulated state
during technical magnetization. 相似文献
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N. I. Kourov A. V. Korolev Yu. V. Knyazev E. G. Gerasimov M. A. Korotin 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(8):1066-1068
Complex investigation of the properties of PdMn x Fe1? x ternary alloys with interacting magnetic and structural order parameters has been performed. It is shown that the complex structural and magnetic state near the transition from the atomically ordered PdFe ferromagnet to the intermetallic antiferromagnetic PdMn compound leads to unusual features not only in magnetic and lattice characteristics but also in electronic properties. 相似文献
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é. Z. Valiev 《Journal of Experimental and Theoretical Physics》2009,108(2):279-285
The exchange striction model is invoked to derive an expression for the entropy of ferromagnetic materials undergoing first- and second-order magnetic phase transitions. The magnetocaloric and barocaloric effects are calculated for the ferromagnet La(Fe0.88Si0.12)13 undergoing a first-order phase transition. The calculated results are in fair agreement with experimental data. The ferromagnet La(Fe0.88Si0.12)13 is used as an example to predict the changes in magnetic and magnetocaloric properties associated with gradual increase in the magnetoelastic coupling constant (i.e., with passage from first- to second-order magnetic transition region). It is shown that stronger magnetoelastic coupling leads to stronger magnetocaloric effects and changes their dependence on magnetic field and pressure. Expressions are obtained for the maximum field- and pressure-induced entropy changes. An analysis is presented of the mechanism responsible for the increase in magnetocaloric and barocaloric effects associated with change from the second- to first-order magnetic phase transition. 相似文献
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S. R. Boidedaev D. R. Dzhuraev B. Yu. Sokolov Sh. Sh. Faiziev 《Optics and Spectroscopy》2009,107(4):651-654
The field dependence of the magnetic linear birefringence (MLB) in easy-plane weak FeBO3:Mg ferromagnet has been investigated. It is found that MLB nonmonotonically (stepwise) tends to a constant value with an
increase in magnetic field at low temperatures. This feature of MLB in FeBO3:Mg is related to the transformation of the crystal magnetic structure during magnetization. 相似文献
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Magnetic contributions to specific heat and entropy have been measured of a metallic ferromagnet CoS2. The critical exponent is anomalously large. The entropy change due to a magnetic ordering is 0.4 R In 2, which suggests an itinerant character of magnetic electrons. 相似文献