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First-principles calculations have been performed on the structural, electronic, and magnetic properties of seven 3d transition-metal (TM) impurities (V, Cr, Mn, Fe, Co, Ni, and Cu) doped armchair (5,5) and zigzag (8,0) beryllium oxide nanotubes (BeONTs). The results show that there exists a structural distortion around the 3d TM impurities with respect to the pristine BeONTs. The magnetic moment increases for V- and Cr-doped BeONTs and reaches a maximum for Mn-doped BeONT, and then decreases for Fe-, Co-, Ni-, and Cu-doped BeONTs successively, consistent with the predicted trend of Hund's rule to maximize the magnetic moments of the doped TM ions. However, the values of the magnetic moments are smaller than the predicted values of Hund's rule due to the strong hybridization between the 2p orbitals of the near O and Be ions of BeONTs and the 3d orbitals of the TM ions. Furthermore, the V-, Co-, and Ni-doped (5,5) and (8,0) BeONTs with half-metal ferromagnetism and thus 100% spin polarization character are good candidates for spintronic applications. [ABSTRACT FROM AUTHOR]

Here, we use half-metallic Co2MnSi (CMS) ferromagnets to prepare CMS/Ag non-local lateral spin valve devices. By optimizing the structural property of CMS wires and the interface quality, device structure of CMS/Ag spin valves, large spin resistance about 4.2mγ can be observed clearly at room temperature when the gap length of two CMS wires is 200 nm. By fitting the spin accumulation signals, we obtained that the spin diffusion length for Ag wire is 290 nm and the spin polarization for CMS wires is 74%. These results indicate that half-metallic ferromagnetic materials can be used in semiconductor-based spin devices. [ABSTRACT FROM AUTHOR]

We investigate theoretically transport characteristics in a graphene-based pseudospinmagnet/superconductor junction, including the s-wave and the d-wave pairing symmetry potential in the superconducting region. It is found that the pseudospin polarization, in sharp contrast to spin polarization in the graphene-based ferromagnet/superconductor junction, holds no influence on the specular Andreev reflection for a negligible Fermi energy. Furthermore, the Fano factor is crucially affected by the zero bias state. Therefore, we suggest here that the findings could shed light on the realization of graphene-based pseudospintronics devices and provide a new way to detect the specular Andreev reflection and the zero bias state in the actual experiments. [ABSTRACT FROM AUTHOR]

We investigated the effects of Mn ions on the spin dynamics of electrons confined in a semiconductor quantum well nearby a Mn-based ferromagnetic layer. Circularly polarized Hanle and time-resolved photoluminescence (PL) measurements were carried out on a set of samples with different Mn delta-doping concentrations. We observe a strong influence of the Mn layer for both the electron lifetime and its spin-relaxation time for high-Mn concentrations, when the electrons significantly overlap with Mn ions. Our results also show that the circular-polarization degree obtained by simple continuous-wave PL measurements is not sufficient to determine the relaxation dynamics due to a compensation effect of the lifetime and the spin-relaxation time. (Some figures may appear in colour only in the online journal) [ABSTRACT FROM AUTHOR]

Electric field control of magnetization allows further miniaturization of integrated circuits for binary bit processing and data storage as it eliminates the need for bulky sophisticated systems to induce magnetic fields. Magnetoelectric coupling inherent to the bulk of multiferroic films or control of spin orientation in magnetic layers via piezoelectric strain in dual component composites have been two approaches standing out. Another magnetoelectric effect is spin-dependent screening that occurs at dielectric/ferromagnet interfaces which is of great importance for spin selective tunnel junctions. Here, we analyze the spin-dependent screening of ferroelectric polarization in a film interfacing ferromagnetic electrodes using the continuity equations in continuum media. The competition between the electrostatic and the magnetochemical potential in the FM electrodes gives rise to a reduction in the net magnetic moment near the interface due to spin mixing, extending to a distance comparable to the Thomas–Fermi screening length. Our continuum media treatment shows that the local spin population in spin subbands near the interfaces can dramatically deviate from bulk, which is in qualitative agreement with recent first principles results. We compute the tunneling currents for the majority and minority spins using the Wentzel–Kramers–Brillouin approximation as a function of ferroelectric polarization. We find that the spin polarization tends to disappear for increasing values of ferroelectric polarization in direct connection with the increase in subband spin population for minority spins at the interface. [ABSTRACT FROM AUTHOR]

Ferromagnetic Heusler compounds have vast and imminent applications for novel devices, smart materials thanks to density functional theory (DFT) based simulations, which have scored out a new approach to study these materials. We forecast the structural stability of Co2TaZ alloys on the basis of total energy calculations and mechanical stability criteria. The elastic constants, robust spin-polarized ferromagnetism and electron densities in these half-metallic alloys are also discussed. The observed structural aspects calculated to predict the stability and equilibrium lattice parameters agree well with the experimental results. The elastic parameters like elastic constants, bulk, Young’s and shear moduli, poison’s and Pugh ratios, melting temperatures, etc have been put together to establish their mechanical properties. The elaborated electronic band structures along with indirect band gaps and spin polarization favour the application of these materials in spintronics and memory device technology. [ABSTRACT FROM AUTHOR]

We theoretically demonstrate a simple way to significantly enhance the spin/valley polarizations and tunneling magnetoresistnace (TMR) in a ferromagnetic-normal-ferromagnetic (FNF) silicene junction by applying a circularly polarized light in the off-resonant regime to the second ferromagnetic (FM) region. We show that the fully spin-polarized current can be realized in certain ranges of light intensity. Increasing the incident energy in the presence of light will induce a transition of perfect spin polarization from positive to negative or vice versa depending on the magnetic configuration (parallel or anti-parallel) of FNF junction. Additionally, under a circularly polarized light, valley polarization is very sensitive to electric field and the perfect valley polarization can be achieved even when staggered electric field is much smaller than exchange field. The most important result we would like to emphasize in this paper is that the perfect spin polarization and 100% TMR induced by a circularly polarized light are completely independent of barrier height in the normal region. Furthermore, the sign reversal of TMR can be observed when the polarized direction of light is changed. A condition for observing the 100% TMR is also reported. Our results are expected to be informative for real applications of a FNF silicene junction, especially in spintronics. [ABSTRACT FROM AUTHOR]

We investigate the specular Andreev reflection and spin-valley resolved conductance of electrons in the ferromagnet-superconductor silicene junction. Our study is based on the tunnelling Hamiltonian and Blonder–Tinkham–Klapwijk theory. First, we acquire the probabilities of Andreev reflection and normal reflection as a function of incident angle and bias voltage. These results show that the Andreev reflection occurs only for the bias voltage, which is smaller than the superconducting gap, and the Andreev reflection processes can be efficiently controlled via a local electric field and ferromagnetic exchange field. Next, we demonstrate the electric field and exchange field-dependent charge conductance, we show that the charge conductance can be suppressed for electric field away from the critical value and enhanced doubly by increasing the exchange field, enabling controllable electronic switching. In particular, one full spin and valley polarized conductance can be achieved in this junction. Our findings reveal the potential of silicene for spin-valleytronic applications. [ABSTRACT FROM AUTHOR]

Co2FeSi thin films are grown on a Si (1 0 0) substrate using ultrahigh-vacuum magnetron sputtering at different substrate temperatures from 300 °C to 550 °C. The films are characterized using grazing incidence x-ray diffraction, magnetization, and ferromagnetic resonance and temperature-dependent resistivity measurements. The films deposited at 450 °C (TS450) have better magnetic as well as structural properties with the minimum disorder. The temperature dependence of line-width () suggests two-magnon scattering is responsible for the line broadening. The correlation between the disorder and extrinsic broadening of the line-width is brought out clearly for the first time in Co2FeSi thin films. TS450 film has minimum (33 Oe) and Gilbert damping parameter (α  =  0.005) at room temperature making it ideal for spintronic applications. [ABSTRACT FROM AUTHOR]

Co-based full-Heusler alloys, such as Co2MnSi and Co2MnGe, are expected to be used as half-metallic ferromagnetic material, which has complete spin polarization. They are the most promising materials for realizing half-metallicity at room temperature due to their high Curie temperature. The optimization of the magnetic damping constant of ferromagnetic materials is extremely important for achieving high-speed magnetization switching and reducing critical current density for spin torque transfer switching. We have systematically investigated the magnetic damping constant in Co-based full Heusler alloy epitaxial films. We found that the Gilbert damping constant seems to be roughly proportional to the total density of states at the Fermi level (EF) by first principle calculation. A very small magnetic damping constant of 0.003 in the Co2Fe0.4Mn0.6Si epitaxial film was demonstrated. The small magnetic damping constant in Co2FexMn1−xSi films with x < 0.6 can be attributed to the half-metallicity of Heusler alloys. Co-based full Heusler alloys with both half-metallicity and small magnetic damping will be very useful for future applications based on spintronic devices. [ABSTRACT FROM AUTHOR]

On the basis of the torque correlation model for the Gilbert damping constant α, we perform the first principles calculation for α for Co-based Heusler alloys, Co2MnAl (CMA), Co2MnSi (CMS), and Co2FeSi (CFS). In the ordered (L21) and partially disordered (B2) structures, the calculated values of α reflect half-metallicity or the gap structure around the Fermi level, EF, i.e. CMS with 100% spin-polarization has the smallest value. The valence electron number dependence of α follows the experimental trend. However, the calculated values are almost a factor of ten smaller than the measured ones. Although the α values are larger in the completely disordered (A2) structure, they are not as large as the experimental results. Therefore, the decreasing degree of order or the breakdown of the half-metallicity is not responsible for the discrepancy. [ABSTRACT FROM AUTHOR]

We demonstrate opto-spintronics using Fe-doped Indium Phosphide (InP). The method is based on optical orientation of InP conduction electron spins which are electrically detected in planar InP/oxide/Ni tunnel spin filters. We separate the optical excitation from electrical detection, avoiding thus additional interactions of photons with the ferromagnet. Interface engineering provides a surface iron accumulation and semiconducting Fe:In2O3 in the oxide tunnel barrier. The spin filtering effect switches to positive or negative asymmetry, depending on the Fe concentration in Fex:InP. With respect to the Fe-like electronic structure of these oxides, we can explain the opposite spin selection mechanisms as interface effects. In the temperature region where the InP mobility peaks, we find a maximum of spin-dependent asymmetry of in semi-insulating Fe:InP (001), and show the electrical spin detection in hyperpolarized InP also at room temperature. Such robust electronic spin detection in an InP nanodevice is planned to complement dynamic nuclear polarization experiments. [ABSTRACT FROM AUTHOR]

We study the generation of spin polarization in monolayer graphene in the presence of Rashba spin–orbit interaction (SOI) and a ferromagnetic (FM) stripe. It is shown that Rashba SOI alone can generate an in-plane (x–y plane) spin polarization, but a FM stripe with magnetization parallel to the current direction cannot generate any spin polarization. A combination of the Rashba SOI and the magnetic field of a FM stripe can increase the spin polarization to a value close to 100%, and the polarization components can be found along the x, y and z directions. The attainment of highly spin polarized current using the Rashba SOI and FM effect could have useful applications in the development of graphene spintronics. [ABSTRACT FROM AUTHOR]

We report on the electronic and optical properties of two theoretically predicted stable spinel compounds of the form ZnBO, where B = Ni or Cu; neither compound has been previously synthesized, so we compare them to the previously studied p-type ZnCoO spinel. These new materials exhibit spin polarization, which is useful for spintronics applications, and broad conductivity maxima near the valence band edge that indicate good p-type dopability. We show that electrons on the octahedrally coordinated Zn atom fall deep within the valence band and do not contribute significantly to the electronic structure near the band edge of the material, while the O and tetrahedrally coordinated B electrons hybridize broadly in the shallow valence states, resulting in increasing curvature (i.e., decreased electron effective mass) of valence bands near the band edge. In particular, ZnCuO exhibits high electrical conductivities in the p-doping region near the valence band edge that, at , are twice the maximum found for ZnCoO , a previously synthesized compound in this class of materials. This material also exhibits ferromagnetism in all of its most stable structures, which makes it a good candidate for further study as a dilute magnetic semiconductor. [ABSTRACT FROM AUTHOR]

Spin injection at the interface of Fe3O4/stearic acid molecule is investigated in a comparative study of Fe3O4 nanoparticles chemically bonded with molecules (ChemNPs) and Fe3O4 nanoparticles with physically absorbed molecules (PhyNPs). The resistance of PhyNPs is two orders of magnitude larger than that of ChemNPs, indicating that the resistance of PhyNPs is dominated by the energy barrier at the Fe3O4–molecule interface. A magnetoresistance of −12% under a field of 5.8 kOe at room temperature is observed in ChemNPs, in sharp contrast to the zero magnetoresistance in PhyNPs, reflecting that the chemical bonding is crucial for spin injection. We attribute this result to the induced magnetic moment in molecules by proximity effect, which is likely the origin of the spin-dependent tunnelling through molecules. In addition, the estimated relatively large spin polarization of ChemNPs suggests electronic hybridization at the interface and improved oxygen stoichiometry of the Fe3O4 surface. [ABSTRACT FROM AUTHOR]