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1 Apr 2009

Volume 105, Issue 7, Articles (07xxxx)

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back to top Spin Dependent Properties and Spin Manipulation for Spintronics

Ab initio calculation of intrinsic spin Hall conductivity of Pd and Au

G. Y. Guo

J. Appl. Phys. 105, 07C701 (2009); http://dx.doi.org/10.1063/1.3054362 (3 pages) | Cited 2 times

Online Publication Date: 30 January 2009

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An ab initio relativistic band structure calculation of spin Hall conductivity (SHC) (σxyz) in Pd and Au metals has been performed. It is found that at low temperatures, intrinsic SHCs for Pd and Au are, respectively, ∼ 1400 and ∼ 400 (ℏ/e)(Ω cm)−1. The large SHC in Pd comes from the resonant contribution from the spin-orbit splitting of the doubly degenerated 4d bands near the Fermi level at symmetry Γ and X points, and the smaller SHC in Au is due to the broad free-electron-like 6s6p bands. However, as the temperature increases, the SHC in Pd decreases monotonically and reduces to ∼ 330 (ℏ/e)(Ω cm)−1 at 300 K, while the SHC in Au increases steadily and reaches ∼ 750 (ℏ/e)(Ω cm)−1 at room temperature. This indicates that the gigantic spin Hall effect [σxyz ≈ 105 (ℏ/e)(Ω cm)−1] observed recently in the Au/FePt system [ T. Seki et al., Nature Mater. 7, 125 (2008) ] is due to the extrinsic mechanisms such as the skew scattering by the impurities in Au.
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71.15.Rf Relativistic effects
72.15.Gd Galvanomagnetic and other magnetotransport effects
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
71.20.Be Transition metals and alloys
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)

Effect of polymer processing on spin magnetoresistance in organic structures

D. Dhandapani, A. Rao, N. A. Morley, A. Das, M. Grell, and M. R. J. Gibbs

J. Appl. Phys. 105, 07C702 (2009); http://dx.doi.org/10.1063/1.3056409 (3 pages) | Cited 6 times

Online Publication Date: 2 February 2009

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Results from studies of spin dependent transport in the hole transporting organic semiconductor regioregular poly 3-hexylthiophene (RR-P3HT) are reported. The organic spin valves were grown on glass, with the structure Fe50Co50/RR‐P3HT/Ni81Fe19. RR-P3HT was cast from five different solvents with different boiling points; 1,2,4 trichlorobenzene, toluene, xylene, chloroform, and chlorobenzene. Magnetoresistance measurements were carried out at room temperature. Spin dependent transport was only observed when toluene, xylene, and annealed 1,2,4 trichlorobenzene were used as solvents. Results are interpreted on the basis of differences in the RR-P3HT morphology induced by different solvents under fixed processing conditions.
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72.20.My Galvanomagnetic and other magnetotransport effects
72.25.Dc Spin polarized transport in semiconductors
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
72.80.Le Polymers; organic compounds (including organic semiconductors)

The spin polarization of Mn atoms in paramagnetic CuMn alloys induced by a Co layer

M. Abes, D. Atkinson, B. K. Tanner, T. Charlton, S. Langridge, T. P. A. Hase, M. Ali, C. H. Marrows, A. Neudert, R. J. Hicken, A. Mirone, and D. Arena

J. Appl. Phys. 105, 07C703 (2009); http://dx.doi.org/10.1063/1.3063065 (3 pages) | Cited 1 time

Online Publication Date: 6 February 2009

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Using the surface, interface, and element specificity of x-ray resonant magnetic scattering in combination with x-ray magnetic circular dichroism, we have spatially resolved the polarization, and hence the spin accumulation in Mn high susceptibility material in close proximity to a ferromagnetic layer. The magnetic polarization of Mn and Cu 3d electrons in paramagnetic CuMn layers is detected in a Co/Cu(x)/CuMn structure for varying copper layer thicknesses (x). The size of the Mn and Cu L2–3-edge dichroism shows a decrease in the polarization for increasing copper thickness indicating the dominant interfacial nature of the Cu and Mn spin polarization. The Mn polarization appears to be much higher than that of Cu.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.20.En Metals and alloys
75.50.Cc Other ferromagnetic metals and alloys
78.20.Ls Magneto-optical effects

Tunneling time of spin particle determined by the spin precession method in the Dresselhaus spin orbit semiconductor system

F. Wan, M. B. A. Jalil, and S. G. Tan

J. Appl. Phys. 105, 07C704 (2009); http://dx.doi.org/10.1063/1.3065968 (3 pages) | Cited 1 time

Online Publication Date: 9 February 2009

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We determine the traversal time τ of electrons through a semiconducting barrier by relating it to the precession of its spin due to Dresselhaus spin orbital effect. The precessional angle is obtained by performing a unitary transformation of the spin axis to the effective spin orbit coupling field and determining the change in phase of the transmitted wave function. The calculated τ exhibits counterintuitive trends with respect to barrier geometry and electron energy. The proposed clocking method based on the Dresselhaus effect might have practical advantages over the applied field and simplify experimental efforts to investigate electron tunneling in semiconductor materials.
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73.40.Gk Tunneling
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Nonlinear effective spin-mixing conductance in Pt/Ni80Fe20/Pt thin films

R. Cao, X. Fan, T. Moriyama, and John Q. Xiao

J. Appl. Phys. 105, 07C705 (2009); http://dx.doi.org/10.1063/1.3072443 (3 pages) | Cited 3 times

Online Publication Date: 19 February 2009

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In this study, the effective spin-mixing conductance in Ni80Fe20/Pt was investigated by measuring the interface-induced enhancement of the Gilbert damping constant. Ferromagnetic resonance spectra were measured in coplanar waveguide geometry with different incident microwave powers. The nonlinear behavior of normal Gilbert damping G0 and effective spin-mixing conductance g↑↓ have been observed when the incident microwave power is above a critical ac field hrf of 1.6 Oe. Both phenomena are explained by considering the coupling between spin coherent precession and spin wave modes. This work demonstrates the nonlinear behavior of the effective spin-mixing conductance g↑↓. It suggests that the nonlinear spin wave modes excited at high incident microwave power are detrimental to the spin pumping effect and should be avoided in future spin battery designs. The capability of tuning G0 and g↑↓ through the microwave power is also useful for the fundamental study on the damping mechanism.
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75.30.Ds Spin waves
73.61.At Metal and metallic alloys
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance

Spin motive force in magnetic nanostructures

Jun-ichiro Ohe and Sadamichi Maekawa

J. Appl. Phys. 105, 07C706 (2009); http://dx.doi.org/10.1063/1.3056572 (3 pages) | Cited 8 times

Online Publication Date: 23 February 2009

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In a ferromagnetic metal, a nonconservative force acting on the spin degree of freedom of electrons gives rise to the spin motive force, which is in contrast to the electromotive force acting on the charge degree of electrons. The spin motive force induced by the motion of the magnetic vortex core in a magnetic disk is examined in the numerical simulation method. By introducing the motive force in the Landau–Lifshitz equation for magnetic dynamics, the electromotive force is obtained near the vortex core. The experimental setup for observing the electric field is proposed.
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75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.40.Mg Numerical simulation studies
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Bb Fe and its alloys
75.50.Tt Fine-particle systems; nanocrystalline materials
72.25.Ba Spin polarized transport in metals

Tunneling magnetoresistance in (Ga,Mn)As/Al–O/CoFeB hybrid structures

G. X. Du, M. Ramesh Babu, X. F. Han, J. J. Deng, W. Z. Wang, J. H. Zhao, W. D. Wang, and Jinke Tang

J. Appl. Phys. 105, 07C707 (2009); http://dx.doi.org/10.1063/1.3068418 (3 pages) | Cited 1 time

Online Publication Date: 23 February 2009

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Tunneling magnetoresistance (TMR) in Ga0.92Mn0.08As/Al–O/Co40Fe40B20 trilayer hybrid structure as a function of temperature from 10 to 50 K with magnetic field |H| ≤ 2000 Oe has been studied. TMR ratio of 1.6% at low fields at 10 K was achieved with the applied current of 1 μA. The behavior of junction resistance was well explained by the tunneling resistance across the barrier. Strong bias dependences of magnetoresistance and junction resistance were presented.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.50.Pp Magnetic semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
73.61.Ey III-V semiconductors

Effects of carrier mobility and morphology in organic semiconductor spin valves

Yaohua Liu, Taegweon Lee, Howard E. Katz, and Daniel H. Reich

J. Appl. Phys. 105, 07C708 (2009); http://dx.doi.org/10.1063/1.3068468 (3 pages) | Cited 2 times

Online Publication Date: 27 February 2009

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We studied spin transport in four organic semiconductors (OSCs) with different electronic properties. Magnetoresistance (MR) effects were observed up to room temperature in junctions based on an electron-carrying OSC, tris(8-hyroxyquinoline) aluminum (Alq3) and a hole-carrying OSC, copper phthalocyanine (CuPc). The MR shows similar temperature dependence for these two OSCs. We also investigated junctions based on two high lateral mobility electron-carrying OSCs, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and N,N′-bis(4-trifluoromethylbenzyl)-1,4,5,8-naphthalenetetracarboxylic diimide (CF3-NTCDI). However, these junctions showed much weaker spin transport effects. Morphological studies suggest that these high mobility OSC films have much rougher surfaces than either Alq3 or CuPc, therefore the degradation of spin transport may originate from enhanced scattering due to the rougher FM/OSC interfaces. Our study shows that FM/OSC interfaces play an important role for spin transport in organic devices and need further exploration.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
73.40.Ns Metal-nonmetal contacts
75.47.Pq Other materials
72.20.Ee Mobility edges; hopping transport

Conductance modulation and spin polarization in anisotropic Rashba ring interferometers

M. B. A. Jalil and S. G. Tan

J. Appl. Phys. 105, 07C709 (2009); http://dx.doi.org/10.1063/1.3075991 (3 pages)

Online Publication Date: 4 March 2009

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We investigate the ballistic spin and charge transport in an anisotropic Rashba ring interferometer with an asymmetry due to either (i) a variable azimuthal position (ϕc) of the collector electrode, or (ii) different Rashba constants (αRu and αRl) for the upper and lower halves of the ring. The transmitted conductance and spin polarization are calculated at the collector by considering the interference of the electron wave functions from the upper and lower halves. These show strong modulation with ϕc and αR, the latter of which can be varied with a gate voltage.
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07.60.Ly Interferometers
72.25.-b Spin polarized transport
73.23.Ad Ballistic transport

Interlayer thickness dependence of 90° exchange coupling in Co2MnAl/Cr/Co2MnAl epitaxial trilayer structures

S. Bosu, Y. Sakuraba, K. Saito, H. Wang, S. Mitani, K. Takanashi, C. Y. You, and K. Hono

J. Appl. Phys. 105, 07C710 (2009); http://dx.doi.org/10.1063/1.3070610 (3 pages) | Cited 4 times

Online Publication Date: 5 March 2009

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The spacer layer thickness dependence of interlayer exchange coupling has been investigated in the fully epitaxial trilayers of the Co2MnAl (CMA)/Cr/CMA structure. A series of high-quality samples of CMA (20 nm)/Cr (tCr = 0.3–8.1 nm)/CMA (10 nm) trilayers was prepared on a MgO substrate by ultrahigh vacuum compatible dc sputtering. Comparison of the results of the experiments and the simulations of magnetization curves revealed novel behavior, dominating the 90° coupling and the absence of 180° coupling. No clear oscillation, only a peak of the 90° coupling strength (J2 ∼ −0.68 erg/cm2), was observed at tCr = 1.2 nm.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.15.Cd Deposition by sputtering
75.30.Et Exchange and superexchange interactions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Current and shot noise measurements in a carbon nanotube-based spin diode (invited)

Christopher A. Merchant and Nina Marković

J. Appl. Phys. 105, 07C711 (2009); http://dx.doi.org/10.1063/1.3072020 (4 pages) | Cited 7 times

Online Publication Date: 20 March 2009

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Low-temperature measurements of asymmetric carbon nanotube (CNT) quantum dots are reported. The CNTs are end-contacted with one ferromagnetic and one normal-metal electrode. The measurements show a spin-dependent rectification of the current caused by the asymmetry of the device. This rectification occurs for gate voltages for which the normal-metal lead is resonant with a level of the quantum dot. At the gate voltages at which the current is at the maximum current, a significant decrease in the current shot noise is observed.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
73.40.Ns Metal-nonmetal contacts
73.40.Ei Rectification
85.35.Kt Nanotube devices

Spin Hall effect in Molybdenum wires

M. Morota, K. Ohnishi, T. Kimura, and Y. Otani

J. Appl. Phys. 105, 07C712 (2009); http://dx.doi.org/10.1063/1.3076145 (3 pages) | Cited 3 times

Online Publication Date: 24 March 2009

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The spin Hall effect in molybdenum wires has been experimentally investigated by means of spin absorption method using lateral spin valve structure. The spin Hall conductivity of Mo wire is negative and decreases with increasing the resistivity. These tendencies are surprisingly consistent with the recent theoretical calculation based on the intrinsic spin Hall effect.
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72.25.Ba Spin polarized transport in metals
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
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