The magnetic and electronic properties of both linear and zigzag atomic chains of all 3d transition metals have been calculated within density functional theory with the generalized gradient approximation. The underlying atomic structures were determined theoretically. It is found that all the zigzag chains except the nonmagnetic Ni and antiferromagnetic ͑AF͒ Fe chains, which form a twisted two-legger ladder, look like a corner-sharing triangle ribbon and have a lower total energy than the corresponding linear chains. All the 3d transition metals in both linear and zigzag structures have a stable or metastable ferromagnetic ͑FM͒ state. Furthermore, in the V, Cr, Mn, Fe, and Co linear chains and Cr, Mn, Fe, Co, and Ni zigzag chains, a stable or metastable AF state also exists. In the Sc, Ti, Fe, Co, and Ni linear structures, the FM state is the ground state, while in the V, Cr, and Mn linear chains, the AF state is the ground state. The electronic spin polarization at the Fermi level in the FM Sc, V, Mn, Fe, Co, and Ni linear chains is close to 90% or above, suggesting that these nanostructures may have applications in spin-transport devices. Interestingly, the V, Cr, Mn, and Fe linear chains show a giant magnetolattice expansion of up to 54%. In the zigzag structure, the AF state is more stable than the FM state only in the Cr chain. Both the electronic magnetocrystalline anisotropy and magnetic dipolar ͑shape͒ anisotropy energies are calculated. It is found that the shape anisotropy energy may be comparable to the electronic one and always prefers the axial magnetization in both the linear and zigzag structures. In the zigzag chains, there is also a pronounced shape anisotropy in the plane perpendicular to the chain axis. Nonetheless, in the FM Ti, Mn, and Co linear chains and AF Cr, Mn, and Fe linear chains, the electronic anisotropy is perpendicular, and it is so large in the FM Ti and Co linear chains as well as in AF Cr, Mn, and Fe linear chains that the easy magnetization axis is perpendicular. In the AF Cr and FM Ni zigzag structures, the easy magnetization direction is also perpendicular to the chain axis, but in the ribbon plane. Remarkably, the axial magnetic anisotropy in the FM Ni linear chain is gigantic, being ϳ12 meV/atom, suggesting that Ni nanowires may have applications in ultrahigh density magnetic memories and hard disks. Interestingly, there is a spin-reorientation transition in the FM Fe and Co linear chains when the chains are compressed or elongated. Large orbital magnetic moment is found in the FM Fe, Co, and Ni linear chains. Finally, the band structure and density of states of the nanowires have also been calculated to identify the electronic origin of the magnetocrystalline anisotropy and orbital magnetic moment.

Based on first principles density functional calculations of the intrinsic anomalous and spin Hall conductivities, we predict that the charge Hall current in Co-based full Heusler compounds Co 2 XZ (X = Cr and Mn; Z = Al, Si, Ga, Ge, In and Sn), except Co 2 CrGa, would be almost fully spin polarized, even though Co 2 MnAl, Co 2 MnGa, Co 2 MnIn and Co 2 MnSn do not have a halfmetallic band structure. Furthermore, the ratio of the associated spin current to the charge Hall current is slightly larger than 1.0. This suggests that these Co-based Heusler compounds, especially Co 2 MnAl, Co 2 MnGa and Co 2 MnIn which are found to have large anomalous and spin Hall conductivities, might be called anomalous Hall half-metals and could have valuable applications in spintronics such as spin valves as well as magnetoresistive and spin-torquedriven nanodevices. These interesting findings are discussed in terms of the calculated electronic band structures, magnetic moments and also anomalous and spin Hall conductivities as a function of the Fermi level.

BiTeI exhibits large Rashba spin splitting due to its noncentrosymmetric crystal structure. The study of chemical doping effect is important in order to either tune the Fermi level or refine the crystal quality. Here, we report the magneto-transport measurement in high quality BiTeI single crystals with different copper dopings. We found that a small amount of copper doping improves the crystal quality significantly, which is supported by the transport data showing higher Hall mobility and larger amplitude in Shubnikov-de Haas oscillation at low temperature. Two distinct frequencies in Shubnikov-de Haas oscillation were observed giving extremal Fermi surface areas of AS = 9.1×10 12 cm −2 and AL = 3.47×10 14 cm −2 with corresponding cyclotron masses m * S = 0.0353 me and m * L = 0.178 me, respectively. Those results are further compared with relativistic band structure calculations using three reported Te and I refined or calculated positions. Our analysis infers the crucial role of Bi-Te bond length in the observed large bulk Rashba-type spin splitting effect in BiTeI. PACS numbers:BiTeI emerges as an intriguing material that shows a large Rashba effect [1-3] and a possible topological phase transition under pressure [4]. Its crystal structure comprises alternating layers of bismuth (Bi), tellurium (Te) and iodine (I) each with trigonal planar lattice as illustrated in Fig. 1(a). It was proposed [5] to constitute a semi-ionic structure along the stacking direction, where (BiTe) + layer is positively charged and (Bi-I) layer is ionic. Angle-resolved photo-emission spectroscopy experiments (ARPES) [1,6] have revealed evidence for the giant Rashba spin splitting, and its bulk nature was further confirmed by bulk-sensitive optical spectroscopy [7] and soft x-ray ARPES [8]. When comparing to band structure calculation, the Te and I coordinations turn out to be crucial parameters that can result in dramatic difference in the calculated band property. There are three different Te and I coordinations reported in the literature: coordination A with Te(2/3,1/3,0.6928) and I(1/3,2/3,0.2510) from the refinement analysis of X-ray experiment [5], as well as coordination B with Te(2/3,1/3,0.7111) and I(1/3,2/3,0.2609) [9], and coordination C with Te(2/3,1/3,0.7482) and I(1/3,2/3,0.3076) [10], from two different theoretical structural determinations using the same band structure method. Regardless of the small variation, only coordination C with a shortest Bi-Te bond length (d Bi−Te = 3.05Å) gives rise to a giant Rashba spin-splitting in the bulk band with a Rashba parameter α R ∼ = 5.4 eVÅ according to our calculations, which may infer a close connection between d Bi−Te and its Rashba effect.In this paper, we show magneto-transport measurement results on high quality Cu x BiTeI single crystals with copper (Cu) doping x up to 0.2. Comparing to earlier works on Shubnikov-de Haas (SdH) oscillations [11,12], the SdH oscillation in our crystals exhibits two distinct frequencies derived from a large Fermi surface (LFS) and a small F...

An extensive ab initio study of the physical properties of both linear and zigzag atomic chains of all 4d and 5d transition metals (TM) within the generalized gradient approximation by using the accurate projector-augmented wave method, has been carried out. The atomic structures of equilibrium and metastable states were theoretically determined. All the TM linear chains are found to be unstable against the corresponding zigzag structures. All the TM chains, except Nb, Ag and La, have a stable (or metastable) magnetic state in either the linear or zigzag or both structures. Magnetic states appear also in the sufficiently stretched Nb and La linear chains and in the largely compressed Y and La chains. The spin magnetic moments in the Mo, Tc, Ru, Rh, W, Re chains could be large (≥1.0 µB/atom). Structural transformation from the linear to zigzag chains could suppress the magnetism already in the linear chain, induce the magnetism in the zigzag structure, and also cause a change of the magnetic state (ferromagnetic to antiferroamgetic or vice verse). The calculations including the spin-orbit coupling reveal that the orbital moments in the Zr, Tc, Ru, Rh, Pd, Hf, Ta, W, Re, Os, Ir and Pt chains could be rather large (≥0.1 µB/atom). Importantly, large magnetic anisotropy energy (≥1.0 meV/atom) is found in most of the magnetic TM chains, suggesting that these nanowires could have fascinating applications in ultrahigh density magnetic memories and hard disks. In particular, giant magnetic anisotropy energy (≥10.0 meV/atom) could appear in the Ru, Re, Rh, and Ir chains. Furthermore, the magnetic anisotropy energy in several elongated linear chains could be as large as 40.0 meV/atom. A spin-reorientation transition occurs in the Ru, Ir, Ta, Zr, La and Zr, Ru, La, Ta and Ir linear chains when they are elongated. Remarkably, all the 5d as well as Tc and Pd chains show the colossal magnetic anisotropy (i.e., it is impossible to rotate magnetization into certain directions). Finally, the electronic band structure and density of states of the nanowires have also been calculated in order to understand the electronic origin of the large magnetic anisotropy and orbital magnetic moment as well as to estimate the conduction electron spin polarization.