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1.
用紧束缚近似线性Muffin-tin轨道的方法计算了稀磁半导体(In1-xMnx)As(x=1/2,1/4和1/8)的晶格常数,磁性和电子结构.给出了Mn掺杂浓度的变化对(In1-xMnx)As的晶格常数,磁性和电子结构的影响.  相似文献   

2.
采用基于密度泛函理论的平面波赝势方法,研究了双钙钛矿氧化物Ba2-xSrxFeMoO6(x=0,1,2)的电子结构和磁性。为分析该系列氧化物电子结构和磁性随掺杂浓度的变化规律,在广义梯度近似下计算了其能带结构、态密度和磁矩。其计算结果表明,Ba2-xSrxFeMoO6体系的晶格常数和总磁矩由于Sr掺杂有所降低,与实验结果符合较好。  相似文献   

3.
采用基于密度泛函理论的第一性原理平面波超软赝势法计算了不同浓度Mn掺杂GaN(Ga1-xMnxN,x=0.0625和0.1250)的晶格常数、能带结构和态密度,分析比较了掺杂前后GaN的电子结构和磁性.结果表明:Mn掺入后体系仍为直接带隙半导体,带隙宽度随Mn含量的增加逐步增大.Mn掺杂GaN均使得N2p与Mn3d轨道杂化,产生自旋极化杂质带,自旋向上的能带占据费米面,掺杂后的Ga1-xMnxN表现为半金属铁磁性,适合自旋注入;随着Mn掺杂浓度的增加,体系的半金属性有所增强.  相似文献   

4.
采用基于密度泛函理论的第一性原理平面波超软赝势法计算了不同浓度Mn掺杂GaN(Ga1-xMnxN, x=0.0625和0.1250)的晶格常数、能带结构和态密度,分析比较了掺杂前后GaN的电子结构和磁性。结果表明:Mn掺入后体系仍为直接带隙半导体,带隙宽度随Mn含量的增加逐步增大。Mn掺杂GaN均使得N 2p与Mn 3d轨道杂化,产生自旋极化杂质带,自旋向上的能带占据费米面,掺杂后的Ga1-xMnxN表现为半金属铁磁性,适合自旋注入;随着Mn掺杂浓度的增加,体系的半金属性有所增强。  相似文献   

5.
基于密度泛函理论(DFT),使用局域密度近似(LDA)研究了Heusler合金Cu1-xFex MnSb的电子结构和反铁磁-铁磁相变.研究发现,两种磁状态下的合金晶格常数随掺杂浓度x变化很好地满足Vegard定理.当x0.5时,铁磁态合金的总磁矩很好地符合SP规律,然而当x0.5时,却发生了明显的偏离.由于整个体系存在RKKY和超交换磁耦合的竞争,因而在x=0.25时,我们观察到了独特的反铁磁—铁磁相变.进一步的态密度分析发现,Cu的掺杂浓度可以有效调整铁磁态合金的费米面位置,并且反铁磁态合金由于不同自旋方向的Mn原子的分波态密度相互补偿,总态密度形成了几乎完全对称的自旋向上带和自旋向下带.  相似文献   

6.
通过固相反应法制备了尖晶石氧化物Mn1-xZnxCr2O4(0.0≤x≤1.0)多晶系列样品,并对其晶体结构和磁性进行了系统研究.研究结果表明,系列样品具有立方尖晶石结构,随Zn掺杂浓度x增大,晶格常数单调减小,体系的阻挫因子逐渐增大.低温下MnCr2O4表现为共线亚铁磁和螺旋亚铁磁的共存.当x≤0.4时,随着x增大,4.5T磁场下所测量的磁化强度逐渐减小,矫顽力逐渐增大,表明体系中的螺旋亚铁磁成分逐渐增多.随着x进一步增加,样品x=0.6和0.8表现为自旋玻璃态特征,最终在x=1.0时转变为强阻挫的反铁磁态.  相似文献   

7.
利用第一性原理计算了Inverse-Heusler合金Ti_2Co_(1-x)Ni_xGa的半金属性、磁性和电子性质.计算结果表明Ti_2Co_(1-x)Ni_xGa的原胞总磁矩和晶格常数随着x的增加而增加.由于过渡金属原子之间的直接杂化和sp电子的调节,原胞总磁矩和晶格常数随掺杂浓度x的改变而改变,并与Slater Pauling规则形成一定的差异.当Ni的掺杂浓度x=0.5时,Ti_2Co_(1-x)Ni_xGa合金的费米面在自旋向下带隙的中间位置,因而可以判定Ti2Co0.5Ni0.5Ga将具有最佳的半金属稳定性.  相似文献   

8.
陈萝娜  刘叶烽  张继业  杨炯  邢娟娟  骆军  张文清 《物理学报》2017,66(16):167201-167201
采用熔融-淬火方法制备了Cu_(2.95)Ga_xSb_(1-x)Se_4(x=0,0.01,0.02和0.04)样品,系统地研究了Ga在Sb位掺杂对Cu_3SbSe_4热电性能的影响.研究结果表明,少量的Ga掺杂(x=0.01)可以有效提高空穴浓度,抑制本征激发,改善样品的电输运性能.掺Ga样品在625 K时功率因子达到最大值10μW/cm·K~2,比未掺Ga的Cu_(2.95)SbSe_4样品提高了约一倍.但是随着Ga掺杂浓度的进一步提高,缺陷对载流子的散射增强,同时载流子有效质量增大,导致载流子迁移率急剧下降.因此Ga含量增加反而使样品的电性能恶化.在热输运方面,Ga掺杂可以有效降低双极扩散对热导率的贡献,同时掺杂引入的点缺陷对高频声子有较强的散射作用,因此高温区的热导率明显降低.最终该体系在664 K时获得最大ZT值0.53,比未掺Ga的样品提高了近50%.  相似文献   

9.
研究了(La1-xYx)2/3Ca1/3MnO3(0.0≤x≤0.3)体系的磁特性,给出了磁转变温度Tc与La位平均离子尺寸之间的关联.结果表明,随Y掺杂浓度的增加,金属-绝缘转变(M-I)温度TMI向低温区移动,对应的峰值电阻率ρp升高,对x=0.3样品而言,较未替代样品(x=0.0)增幅达8个数量级之多,指出由于Y的掺入而致使La位平均离子半径()减少以及局域晶格结构畸变引起的.磁性测量表明了在x>0.1的高浓度区域,随着x的增加,反铁磁性相互作用逐渐增强,导致x=0.2和x=0.3的样品在35K左右出现了自旋玻璃态.  相似文献   

10.
采用Sn自熔剂法制备了具有n型传导的VIII型Ba8Ga16 xGexSn30(0 x 1.0)单晶笼合物,并对其结构和热电特性进行研究.研究结果表明:Ge在单晶中的实际含量较少,随着掺杂量的增加样品的晶格常数略有减小,Ge掺杂后样品的载流子浓度较掺杂前低,迁移率增加;所有样品的Seebeck系数均为负值,且绝对值较未掺杂样品低,但Ge掺杂后样品的电导率提高了62%;x=0.5的样品在500 K附近取得最大ZT值1.25.  相似文献   

11.
The possibility of half-metallic antiferromagnetism, a special case of ferrimagnetism with a compensated magnetization, in the diluted magnetic semiconductors is highlighted on the basis of the first-principles electronic structure calculation. As typical examples, the electrical and magnetic properties of II-VI compound semiconductors doped with 3d transition metal ion pairs--(V, Co) and (Fe, Cr)--are discussed.  相似文献   

12.
采用基于密度泛函理论的第一性原理计算法研究了新型稀磁半导体Li_(1±)_y(Zn_(1-)_xFe_x)P (x=0, 0.0625;y=0, 0.0625)的电子结构、磁性及光学性质.结果表明,Fe的掺入使体系产生自旋极化杂质带,Fe的3d态与Li2s态,Zn4s态以及P3p态的态密度峰在费米能级处出现重叠,产生sp-d轨道杂化,此时体系净磁矩最大,材料表现出金属性,导电性增强.当Li空位时,导电性减弱,但杂质带宽度最大,居里温度最高.而Li填隙时,体系形成能最低,材料变为半金属性,表现为100%自旋注入,表明掺杂体系的磁性和电性可以分别通过Fe的掺入和Li的含量进行调控.对比光学性质发现,Li空位时,在介电函数虚部和复折射率函数的低能区出现新峰,扩大了对低频电磁波的吸收范围.能量损失函数表明掺杂体系具有明显的蓝移效应,且Li填隙时有更强的等离子共振频率.  相似文献   

13.
First-principles calculations are performed to investigate the electronic structures and magnetic properties of(Fe, Co)-codoped 4H-SiC using the generalized gradient approximation plus Hubbard U method. We find that 4H-SiC doped with an isolated Fe atom and an isolated Co atom produces a total magnetic moment of 5.98 μ_B and 6.00 μ_B respectively. We estimate T_C of about 263.1 K for the(Fe, Co)-codoped 4H-SiC system. We study ferromagnetic and antiferromagnetic coupling in(Fe, Co)-codoped 4H-SiC. Ferromagnetic behavior is observed.The strong ferromagnetic couplings between local magnetic moments can be attributed to p–d hybridization between Fe, Co and neighboring C. However, the(Fe, Co, V_(Si))-codoped 4H-SiC system shows antiferromagnetic coupling when an Si vacancy is introduced in the same 4H-SiC supercell. The results may be helpful for further study on transition metal-codoped systems.  相似文献   

14.
We have investigated the electronic and magnetic properties of the room temperature ferromagnetic diluted magnetic semiconductor (DMS) (Zn,Cr)Te with density functional calculations. The electronic and magnetic properties of (Zn,Cr)Te are very similar with those of the typical DMS (Ga,Mn)As. The stronger ionicity of ZnTe plays a key role in the electronic and magnetic properties of (Zn,Cr)Te.  相似文献   

15.
In this work, we aim to examine the spin-polarized electronic band structures, the local densities of states as well as the magnetism of Zn1−xTMxSe (TM=Cr, Fe, Co and Ni) diluted magnetic semiconductors in the ferromagnetic (FM) and antiferromagnetic (AFM) phases, and with 25% of TM. The calculations are performed by the developed full-potential augmented plane wave plus local orbitals method within the spin density functional theory. As exchange-correlation potential we used the generalized gradient approximation (GGA) form. We treated the ferromagnetic and antiferromagnetic phases and we found that all compounds are stable in the ferromagnetic structure. Structural properties are computed after total energy minimization. Our results show that the cohesive energies of Zn0.75TM0.25Se are greater than that of zinc blende ZnSe. We discuss the electronic structures, total and partial densities of states, local moments and the p–d exchange splitting. Furthermore, we found that p–d hybridization reduces the local magnetic moment of TM and produces small local magnetic moments on the nonmagnetic Zn and Se sites. We found also that in the AFM phase the TM local magnetic moments are smaller than in the FM phase; this is due to the greater interaction of the TM d-up and d-down orbitals.  相似文献   

16.
First-principles LMTO-ASA band calculations are performed for Ga1-xFexAs (x = 1, 1/4, 1/8) by assuming supercell structures. It is found that the antiferromagnetic (AFM) state is stable for x = 1/4. For x = 1/8, ferromagnetic(FM) state is more stable than AFM state, and no stable magnetic state exists for x = 1. In both the cases the magneticmoments of As and Ga atoms are parallel to those of the nearest Fe atoms due to the p-d hybridization. Further, theband structure shows rather localized Fe 3d state in the gap, and the parallel polarization is confined rather in thevicinity of Fe site.  相似文献   

17.
Spin- and angle-resolved photoelectron spectroscopy was applied for studies of electronic and magnetic structures of Eu/Gd and Ce/Fe. Ferromagnetic coupling of 4f moments of Eu and Gd was found in the 1 ML Eu/Gd(0 0 0 1) system with high net Eu magnetization at low temperatures reflected by a spin polarization of 15% of the Eu 4f state. In case of the 1 ML Ce/Fe(1 1 0) system the antiparallel orientation of the Ce 4f spins with respect to the magnetization direction of the Fe substrate was observed. Very different shapes of the spin-up and spin-down Ce 4f spectral weights can be explained within periodic Anderson model by spin-dependent hybridization between Ce localized 4f and itinerant valence band states.  相似文献   

18.
王爱玲  毋志民  王聪  胡爱元  赵若禺 《物理学报》2013,62(13):137101-137101
采用基于密度泛函理论的第一性原理平面波超软赝势方法, 对纯LiZnAs, Mn掺杂的LiZnAs, Li过量和不足下Mn掺杂的LiZnAs体系进行几何结构优化, 计算并对比分析了体系的电子结构、半金属性、光学性质及形成能.结果表明新型稀磁半导体Li (Zn0.875Mn0.125) As, Li1.1 (Zn0.875Mn0.125) As和Li0.9 (Zn0.875Mn0.125) As均表现为100%自旋注入, 材料均具有半金属性, Li过量和不足下体系的半金属性明显增强. Li过量可以提高体系的居里温度, 改善材料的导电性, 使体系的形成能降低. 说明LiZnAs半导体可以实现自旋和电荷注入机理的分离, 磁性和电性可以分别通过Mn的掺入和Li的含量进行调控. 进一步对比分析光学性质发现, 低能区的介电函数虚部和复折射率函数明显受到Li的化学计量数的影响. 关键词: Mn掺杂LiZnAs 电子结构 光学性质 第一性原理  相似文献   

19.
The electronic and magnetic properties of wurtzite ZnS semiconductor doped with transition metal (Cr, Mn, Fe, Co, and Ni) atoms are studied by using the first-principle’s method in this paper. The ZnS bulk materials doped with Cr, Fe, and Ni are determined to be half-metallic, while those doped with Mn and Co impurities are found to be semiconducting. These doped transition metal ions have long range interactions mediated through the induced magnetic moments in anions and cations of host semiconductors. These doped ZnS-based diluted magnetic semiconductors seem to be good candidates for the future spintronic applications.  相似文献   

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