Electronic and Magnetic Properties of MnAu Superlattices

Self-consistent ab initio calculations, based on the Density Functional Theory (DFT) approach and using full potential linear augmented plane wave (FLAPW) method, are performed to investigate both electronic and magnetic properties of the MnAu superlattices. Polarized spin and spin-orbit coupling are included in calculations within the framework of the antiferromagnetic state between two adjacent MnAu superlattices. Obtained data from ab initio calculations are used as input for the Monte Carlo simulations to compute other magnetic parameters. On the other hand, and within the framework of Monte Carlo simulations, we examine the magnetic properties in the binary MnAu superlattices modelized by the Mn ion with spin moment, S=5/2. The considered Hamiltonian takes into account the nearest neighbor and second nearest interactions, and an external magnetic field h. The magnetization of the MnAu superlattice is calculated versus temperature for a fixed size. The magnetic hysteresis cycle is established for T=120 K. The effect of magnetization versus the second exchange interaction (J _c ) are established with absence and presence of magnetic field (h).     

Magnetic Properties of Diluted Magnetic Nanowire

A magnetic diluted nanowire with cylindrical structure described by the Ising model is investigated. Using the effective field theory with a probability distribution technique, the influence of the dilution on the phase diagrams, susceptibility and the hysteresis loops are discussed in detail. Novel features are obtained for the thermal variations of longitudinal susceptibility and longitudinal magnetization. We have investigated the magnetic reversal of the system and have found the existence of triple hysteresis loops patterns, affected by the concentration of magnetic atoms, the temperature, and the exchange interaction between the core and the surface shell.     

Fe纳米有序阵列的制备与磁学特性

采用电化学沉积法，在氧化铝模板中成功制备了直径50nm的Fe纳米线的高度有序阵列。纳米线的结构和磁学特性分别用透射电子显微镜（TEM），扫描电子显微镜（SEM），X射线衍射仪（XRD）和振动样品磁力计（VSM）测试。结果表明，Fe纳米线是以fcc结构存在。当外加磁场与纳米线的线轴平行时，测得的矫顽力为21000e，剩磁比为0．89，而当外加磁场与纳米线线轴垂直时，所测得的矫顽力仅为1600e，剩磁比为0．2。这表明纳米线阵列具有明显的各向异性，纳柴癌的易妯方向为纳粜姥姥妯方向．     

合金纳米线电子输运性质的理论计算研究

采用分子动力学模拟纳米管中合金纳米线的结构演化以及纳米线电学特性的变化规律。量子效应导致纳米线的电流电压曲线呈现出非线性特点,且在低电压区会出现电导隙,其宽度是由最高分子占据轨道和最低分子未被占据轨道的差值决定。锡原子的掺杂削弱了原本硅锗合金材料内的电子穿透能力,当锡原子数目占整条纳米线原子数的百分之十甚至更多时,由于库仑阻塞效应,在电流电压曲线图的低电压区,电流随电压的变化甚微;当硅锗锡三者原子比例相同时,纳米线的库仑阻塞效应尤为明显。由于隧穿共振效应,电导随电压的增大出现许多共振峰,并且共振峰的数量也随锡原子比例的增加而增加。     

复合锌镍纳米线结构和磁性研究

采用直流电化学沉积方法,在多孔阳极氧化铝模板纳米孔洞中制备出直径约90nm,长度超过10μm的金属Ni/Zn纳米线有序阵列.通过扫描电子显微镜(SEM),透射电子显微镜(TEM),原子力显微镜(AFM),X射线衍射仪(XRD),振动样品磁强计(VSM)对模板及所制备的样品进行形貌、结构及相关性能的表征和测试.结果表明所制备的Ni/Zn纳米线具有沿[111]方向择优生长特性,易磁化方向沿纳米线长轴方向.     

Preparation and Magnetic Properties of Ni/Pd Multilayer Nanowire Arrays

Ni/Pd multilayer nanowire arrays have been electrodeposited into the nanochannels of porous polycarbonate (PC) template. Current–time profiles obtained during the deposition process were analyzed to understand the mechanism of growth. Synthesized nanowires were fully characterized by X-ray diffraction (XRD), energy dispersive X-ray (EDX), and scanning electron microscopy (SEM). The X-ray diffraction pattern showed that Pd and Ni grow in their face-centered-cubic (FCC) structures. Each nanowire had the same length of ≈4 μm and a diameter of 90 nm. The magnetic properties of the prepared nanowires are different under different electrodepositing conditions. A vibration sample magnetometer (VSM) was used to determine the effect of the Pd content on magnetic properties of final products.     

Electronic and Magnetic Properties of MnSb Compounds

The self-consistent ab initio calculations, based on density functional theory (DFT) approach and using full-potential linear augmented plane wave (FLAPW) method, are performed to investigate both electronic and magnetic properties of the MnSb compounds. Polarized spin and spin-orbit coupling are included in calculations within the framework of the ferromagnetic state between two adjacent Mn atoms. The ferromagnetic energy of MnSb systems is obtained. Magnetic moment considered to lie along the (001) axes are computed. The exchange interactions between the magnetic atoms Mn–Mn in MnSb are given using the mean field theory. Obtained data from ab initio calculations are used as input for the high-temperature series expansions (HTSEs) calculations to compute other magnetic parameters. The HTSEs of the magnetic susceptibility of the magnetic moments in MnSb (m _Mn) is given up to the tenth order series in (x = J ₁(Mn–Mn)/ k _B T). The critical temperature T _C is deduced by HTSEs of the magnetic susceptibility series combined with the Padé approximation method. The critical exponent γ associated with the magnetic susceptibility is deduced as well.     

锰掺杂锯齿型石墨烯纳米带电磁学特性研究

基于密度泛函理论的第一性原理,计算了锰原子单空位掺杂锯齿型石墨烯纳米带6种不同位置时的电磁学特性。结果表明:锰原子掺杂石墨烯纳米带的能带结构对掺杂位置十分敏感。随着锰掺杂位置的变化,掺杂石墨烯纳米带分别表现出半导体性和金属性特征。锰原子掺杂石墨烯纳米带改变了原本的磁性特征,掺杂位置不同,结构磁性特点也不相同,掺杂位置在4号位置时,纳米带实现了由反铁磁态的锯齿型石墨烯纳米带向铁磁性的转化。锰原子掺杂锯齿型石墨烯纳米带可以调制其磁性和能带特性,为石墨烯纳米带在电磁学领域应用提供一定的理论依据。     

Electronic and Magnetic Properties of Os-Doped Rhodium Clusters: a Theoretical Study

The stability and electronic and magnetic properties of Rh_nOs (n=?2–12) clusters in their most stable configurations were systematically studied by using density functional theory (DFT) at M06L/aug-cc-pVDZ level. Calculation of the second-order difference of energies and fragmentation energies exhibited that Rh₃Os, Rh₅Os, Rh₇Os, and Rh₉Os clusters are more stable than any other clusters. The calculated HOMO-LUMO energy gaps of the Rh_nOs clusters are found to be in the range of 0.018 to 0.299 eV, implying that the metallic behavior can appear in these clusters. Accordingly, the Rh_nOs clusters can be employed as heterogeneous nanocatalysts in many chemical reactions. The local Fukui function (\(f_{k}^{-} )\) has also been calculated, and the obtained results reveal that the highest \(f_{k}^{-} \) values are predicted for the Rh atoms. Therefore, the Rh atoms in the clusters are considered the most reactive sites that undergo reactions with electrophilic reagents. The analysis of the magnetic properties of the Rh_nOs clusters shows that the total magnetic moment per atom of these clusters varies from 0.67 to 1.75 µ_B/atom. And, the PDOS analysis reveals that the d orbitals play a crucial role for the magnetism of the Rh_nOs clusters, and the contribution of the s and p orbitals is small.     

First-Principles Study on the Electronic and Magnetic Properties of Zigzag AlN-SiC Nanoribbons

The electronic and magnetic properties of zigzag AlN-SiC nanoribbons are investigated by using the first-principles calculations. The band structures reveal that all the investigated AlN-SiC systems are the magnetic semiconductors, the band gaps of which decrease with the increasing width of the ribbon. The majority spin density is mostly contributed by the edge C atoms with dangling bonds. The total magnetic moments increase with the increasing width of the ribbon and decrease with the increase of the strain. These studies are helpful to the potential applications of the AlN-SiC ribbon in spintronics.     

Magnetic Properties and Reversal Modes of Electrodeposited CoCr Nanowire Arrays with Different Diameters

Journal of Superconductivity and Novel Magnetism - The better understanding of magnetization reversal in impurity added magnetic nanowires (NWs) would allow for their efficient use in future...     

Ab Initio Study of Electronic and Magnetic Properties of Germanene with Different Nonmagnetic Metal Adatoms

Electronic and magnetic properties of two-dimensional (2D) germanene (Ge) with five different adatoms have been analyzed and discussed by the DFT method. Different nonmagnetic metals adsorbed at different sites, on one hand, a magnetic moment is induced by Mg adatom in the germanene. On the other hand, the adsorptions of Al, Ga, Li, and Na show no magnetism. We further study the effect of strain on the magnetism in Mg-adsorbed germanene; we apply an isotropic tensile and compressive strain on the system. On the basis of our calculations, a tunable magnetism shows as the strain increases. The analysis of the PDOS shows that the s–p hybridization between Mg and Ge atoms results in such magnetic behavior. These magneticadsorbed germanene materials might show potential applications in the nanoscale devices.     

Magnetic and Electronic Properties of Point Defects in ZrO2

Using the Korringa–Kohn–Rostoker Coherent Potential Approximation (KKR-CPA) method in connection with the Generalized Gradient Approximation (GGA), we study the magnetic and electronic properties of different point defects in cubic ZrO₂. In particular, we discuss the zirconium interstitial (Zr_i), zirconium antisite (Zr_O), zirconium vacancy (V_Zr), oxygen interstitial (O_i), oxygen antisite (O_Zr), and oxygen vacancy (V_O) defects. It has been shown that oxygen vacancy and zirconium interstitial (V_O, Zr_i) are n-type, while the other point defects are p-type. The magnetic moments are observed only in the oxygen interstitial and antisite (O_i, O_Zr) cases. The corresponding ferromagnetic states are more stable than the spin–glass states. It has been found that the mechanism responsible of such stabilities is the double exchange. Based on Mean Field Approximation (MFA), the Curie temperature (T _C ) is estimated. Moreover, it has been found that the O_i and O_Zr defects provide half-metallic properties being the responsible for ferromagnetism.     

Mn掺杂锶铁氧体SrFe12O19电子结构及磁性的第一性原理研究

为了揭示掺杂离子对具有磁铅石构型的锶铁氧体材料磁性能的影响, 本研究探讨了锶铁氧体及其锰掺杂体系的稳定构型及其磁结构。研究结果表明, 锶铁氧体为亚铁磁性, 与前期的研究结果相吻合。通过比较GGA和GGA+U计算方法, 发现U值的选取对体系的电子结构和原子磁矩有显著影响。当U值为3.7 eV时, 体系由金属性转变为自旋向上带隙为1.71 eV的半导体。原胞总磁矩为40 μ_B。对于Mn替换掺杂的SrFe_12-xMn_xO₁₉体系, 通过不同占据位能量比较, 当单个Mn原子替换(x=0.5)时, Mn离子优先占据Fe (12k)位置; 而当两个Mn原子替换Fe原子(x=1.0)时, 两个Mn分别占据Fe (12k)和Fe (2a)位置。Mn掺杂对锶铁氧体的结构影响较小, 但对于体系的总磁矩和电子结构有较明显的影响。在Mn含量x=0.5和x=1.0时, 自旋向上带隙值分别降低到0.85和0.59 eV, 原胞的总磁矩为39和38 μ_B。本研究可为实验研究提供理论指导。     

First Principles Study of Electronic and Magnetic Properties of DyNiPb and YNiPb Compounds Under Hydrostatic Pressure

Density functional theory calculations have been performed to study the electronic and magnetic properties of DyNiPb and YNiPb compounds. The total energy calculations indicate that at zero pressure the ferromagnetic and nonmagnetic phases are the most stable phases of the DyNiPb and YNiPb compounds respectively. The Pb atom has a negligible contribution to the magnetic properties of DyNiPb compared to the Dy and Ni atoms. The effect of hydrostatic pressure on the magnetic moment of these compounds is also studied. The calculated results show that the YNiPb compound has zero magnetic moment over the whole pressure range considered (p<20 GPa), while in the DyNiPb compound the total and local magnetic moments at the Dy and Ni atomic sites increase with increasing pressure. Furthermore, I have investigated the electric field gradient (EFG) at different atomic sites of these compounds. The contribution of different orbitals to the EFG shows that the strongest anisotropy in the charge distribution is due to the electrons in the p orbitals. The variation of EFG at different atomic positions of the DyNiPb and YNiPb compounds with pressure is not linear and increases with pressure.     

交流电化学沉积FeCo合金纳米线阵列及其磁性能研究

采用二步阳极氧化法制备孔结构高度有序的多孔氧化铝(AAO)模板。在不同Fe2+/Co2+摩尔比的电解液中,利用交流电化学沉积,在模板孔内成功制备了FeCo合金纳米线阵列。分别采用透射电子显微镜(TEM),场发射扫描电子显微镜(FE-SEM),X射线衍射仪(XRD)和震动样品磁强计(VSM)对样品的形貌,结构及磁学性能进行了表征。结果表明,制备的FeCo合金纳米线排列有序,粗细均匀;其直径与模板孔径一致,填充率较高,且具有明显的[110]择优取向。VSM测试结果表明,不同溶液浓度下制备的FeCo合金纳米线阵列均具有良好的垂直磁各向异性,易磁化轴沿着纳米线轴线方向。随着电解液Fe2+/Co2+摩尔比的不同,可在一定范围内对FeCo合金纳米线阵列的磁性进行调控,并对其原因进行了讨论。     

First Principles Study of Electronic,Magnetic, and Optical Properties of TbN and ErN Nanolayers

The electronic, magnetic, and optical properties of TbN and ErN nanolayers in the presence of spin orbit coupling using density functional theory using the WIEN2k package are investigated. The stable phase of TbN and ErN bulk using generalized gradient approximation (GGA) approach is studied. The total and partial electron density of states of ErN and TbN nanolayers with two different thicknesses in ferromagnetic phase within GGA and Engel–Vosko GGA (GGA_EV) approaches is calculated. The total and local magnetic moments of these nanolayers are studied. The calculated magnetic moment at Er atomic position of ErN nanolayer is larger than the corresponding value at Tb atomic position of TbN nanolayer. Furthermore, the real and imaginary parts of the dielectric function and the reflectivity and absorption spectra of these nanolayers within GGA_EV approach are studied.     

High Pressure Effects on Electronic and Magnetic Properties of LaOFeAs Superconductor

The effect of pressure has been studied on structural and electronic properties of LaOFeAs high-T _c superconductor by ab initio density functional theory by using pseudopotential Quantum Espresso code. The lattice parameters and ionic positions in the ambient pressure and some high pressure up to 20 GPa have been calculated. The obtained data versus the simple scaling relation for the ionic positions and distances for mechanical pressures have been discussed. The results of band structure and magnetic moment calculations of this compound versus the applied pressure are presented in this paper. The results are compared with the other experimental and computational data in the literature.