2D Spin-Dependent Electron Scattering by Nanomagnets (original) (raw)
Spin Dependent 2d Electron Scattering on Nanomagnets
2011
Spin injection across an interface. (A) Spin injection from a ferromagnetic material (FM) to a non-magnetic material (NM). Application of an electric charge current through the interface results in injection of a spin-polarized current into NM. (B) Spin injection from a ferromagnetic material (F M 1) to another ferromagnetic material with different magnetization direction
Spin dependent 2D electron scattering by nanomagnets
2011
The 2D scattering problem of an electron by a magnetized nanoparticle is solved in the Born approximation with account of the dipole-dipole interaction of the magnetic moments of electron and nanomagnet. The scattering amplitudes in this problem are the two-component spinors. They are obtained as functions of the electron spin orientation, the electron energy and show anisotropy in scattering angle. The initially polarized beam of electrons scattered by the nanomagnet consists of electrons with no spin flipped and spin flipped. The majority of electrons with no spin flipped are scattered by small angles. The majority electrons with spin flipped are scattered in the vicinity of the scattering angles p=2 and 3p=2. This can be used as one more method of controlling the spin currents.
2D Spin-Dependent Diffraction of Electrons From Periodical Chains of Nanomagnets
Applied Sciences, 2012
The scattering of the unpolarized beams of electrons by nanomagnets in the vicinity of some scattering angles leads to complete spin polarized electrons. This result is obtained with the help of the perturbation theory. The dipole-dipole interaction between the magnetic moment of the nanomagnet and the magnetic moment of electron is treated as perturbation. This interaction is not spherically symmetric. Rather it depends on the electron spin variables. It in turn results in spinor character of the scattering amplitudes. Due to the smallness of the magnetic interactions, the scattering length of this process is very small to be proved experimentally. To enhance the relevant scattering lengths, we considered the diffraction of unpolarized beams of electrons by linear chains of nanomagnets. By tuning the distance between the scatterers it is possible to obtain the diffraction maximum of the scattered electrons at scattering angles which corresponds to complete spin polarization of electrons. It is shown that the total differential scattering length is proportional to N 2 (N is a number of scatterers). Even small number of nanomagnets in the chain helps to obtain experimentally visible enhancement of spin polarization of the scattered electrons.
Half-metallic ferromagnets: From band structure to many-body effects
Reviews of Modern Physics, 2008
A review of new developments in theoretical and experimental electronic structure investigations of half-metallic ferromagnets (HMF) is presented. Being semiconductors for one spin projection and metals for another ones, these substances are promising magnetic materials for applications in spintronics (i.e., spin-dependent electronics). Classification of HMF by the peculiarities of their electronic structure and chemical bonding is discussed. Effects of electron-magnon interaction in HMF and their manifestations in magnetic, spectral, thermodynamic, and transport properties are considered. Especial attention is paid to appearance of non-quasiparticle states in the energy gap, which provide an instructive example of essentially manybody features in the electronic structure. State-of-art electronic calculations for correlated d-systems is discussed, and results for specific HMF (Heusler alloys, zinc-blende structure compounds, CrO 2 , Fe 3 O 4 ) are reviewed. * Electronic address: katsnel@science.ru.nl in comparison with the oxides. Nevertheless, the work on half-metallic sulphides deserves strong support.
On the mechanism of spin-dependent (e,2e) scattering from a ferromagnetic surface
Journal of Physics: Conference Series, 2009
A simple model is suggested for a qualitative analysis of spin-dependent (e,2e) reaction on a ferromagnetic surface. The model is based on the scattering of the primary electron with the average spin projection by the valence electron with the average spin projection < s2>. To test the model the energy distributions of correlated electron pairs are measured for parallel and anti-parallel orientations of the magnetic moment of the cobalt film and polarization vector of the incident beam. The proposed model explains qualitatively the spin-asymmetry of the measured binding energy spectrum.
2D scattering of unpolarized beams of electrons by charged nanomagnets
Journal of Magnetism and Magnetic Materials, 2012
2D spin-dependent scattering of slow unpolarized beams of electrons by charged nanomagnets is analyzed in the Born approximation. The obtained scattering lengths are larger than those from the neutral nanomagnets approximately by one order. It is shown that for particular parameters of the system it is possible to polarize completely the scattered electrons in a narrow range of scattering angles. The most suitable system for realization of these effects is 2D Si electron gas with immersed nanomagnets.
Spin-dependent scattering by a potential barrier on a nanotube
Journal of Physics: Condensed Matter, 2010
The electron spin effects on the surface of a nanotube have been considered through the spin-orbit interaction (SOI), arising from the electron confinement on the surface of the nanotube. This is of the same nature as the Rashba-Bychkov SOI at a semiconductor heterojunction. We estimate the effect of disorder within a potential barrier on the transmission probability. Using a continuum model, we obtained analytic expressions for the spin-split energy bands for electrons on the surface of nanotubes in the presence of SOI. First we calculate analytically the scattering amplitudes from a potential barrier located around the axis of the nanotube into spin-dependent states. The effect of disorder on the scattering process is included phenomenologically and induces a reduction in the transition probability. We analyzed the relative role of SOI and disorder on the transmission probability which depends on the angular and linear momentum of the incoming particle, and its spin orientation. We demonstrated that in the presence of disorder perfect transmission may not be achieved for finite barrier heights.
Two-dimensional electron scattering in regions of nonuniform spin-orbit coupling
2006
We present a theoretical study of elastic spin-dependent electron scattering caused by a nonuniform Rashba spin-orbit coupling strength. Using the spin-generalized method of partial waves the scattering amplitude is exactly derived for the case of a circular shape of scattering region. We found that the polarization of the scattered waves are strongly anisotropic functions of the scattering angle. This feature can be utilized to design a good all-electric spin-polarizer. General properties of the scattering process are also investigated in the high and low energy limits.
Spin current related phenomena in metallic nano-structures
Physica E: Low-dimensional Systems and Nanostructures, 2011
The transport properties of diffusive spin currents have been investigated in lateral ferromagnetic/ nonmagnetic metal hybrid structures. The spin diffusion processes were found strongly dependent on the magnitude of the spin resistances of connected materials. The efficient spin injection and detection are accomplished by optimizing the junction structures on the basis of the spin resistance circuitry. The magnetization switching of a nano-scale ferromagnetic particle and also room temperature spin Hall effect measurements were demonstrated by using an efficient pure-spin-current injection.
Electron Spin Dynamics of Two-Dimensional Layered Materials
Advanced Functional Materials, 2016
The growing library of two-dimensional layered materials is providing researchers with a wealth of opportunity to explore and tune physical phenomena at the nanoscale. Here, we review the experimental and theoretical state-of-art concerning the electron spin dynamics in graphene, silicene, phosphorene, transition metal dichalcogenides, covalent heterostructures of organic molecules and topological materials. The spin transport, chemical and defect induced magnetic moments, and the effect of spin-orbit coupling and spin relaxation, are also discussed in relation to the field of spintronics.
Effects of spin-orbit interactions on tunneling via discrete energy levels in metal nanoparticles
Physical Review …, 1999
The presence of spin-orbit scattering within an aluminum nanoparticle affects measurements of the discrete energy levels within the particle by ͑1͒ reducing the effective g factor below the free-electron value of 2, ͑2͒ causing avoided crossings as a function of magnetic field between predominantly spin-up and predominantly spin-down levels, and ͑3͒ introducing magnetic-field-dependent changes in the amount of current transported by the tunneling resonances. All three effects can be understood in a unified fashion by considering a simple Hamiltonian. Spin-orbit scattering from 4% gold impurities in superconducting aluminum nanoparticles produces no dramatic effect on the superconducting gap at zero magnetic field, but we argue that it does modify the nature of the superconducting transition in a magnetic field. ͓S0163-1829͑99͒10731-8͔ PHYSICAL REVIEW B 15 AUGUST 1999-II VOLUME 60, NUMBER 8 PRB 60 0163-1829/99/60͑8͒/6137͑9͒/$15.00 6137
Physica E: Low-dimensional Systems and Nanostructures, 2002
We developed a crossed magnetic ÿeld technique, which allowed us to probe separately the spin and orbital properties of two-dimensional (2D) electrons. Using this technique, we measured directly the spin susceptibility, the e ective electron mass and g-factor in diluted 2D systems near the metal-insulator transition. All these quantities increase gradually with decreasing electron density: e.g., the susceptibility increases by a factor of 4 at n 1 × 10 11 cm −2. We have also studied the e ect of the in-plane magnetic ÿeld B || on dephasing. At high electron densities (n ¿ 2:5 × 10 11 cm −2), the dephasing time ' decreases with B || much stronger than the momentum relaxation time. At small n, on the contrary, the increase of the dephasing rate with B || is less than that for. In the latter case, the dependence '(B||) can be attributed to enhancement of dephasing by the B ||-induced disorder.
Spin control in heteromagnetic nanostructures
Applied Physics Letters, 2005
The rapidly expanding research in Spintronics, the electronics utilizing the electron spin instead of its charge, is driven by the very interesting potential applications. The actual task is to develop principles for the spin manipulations in spintronic devices. In this Report we suggest and verify experimentally a concept of heteromagnetic semiconductor structures. It is based on spin diffusion between layers of the nanostructure with different magnetic properties and allows controlling the spinswitching rate for magnetic ions. A ten times increase of spin-lattice relaxation rate of magnetic Mn-ions is achieved in (Zn,Mn)Se/(Be,Mn)Te heteromagnetic structures with an inhomogeneous distribution of Mn-ions.
Antiferromagnetic molecular nanomagnets with odd- numbered coupled spins
– In recent years, studies on cyclic molecular nanomagnets have captivated the attention of researchers. These magnets are finite in size and contain very large spins. They are interesting because they possess macroscopic quantum tunneling of Néel vectors. For antiferromagnetic molecular nanomagnets with finite number of even-numbered coupled spins, tunneling involves two classical localized Néel ground states separated by a magnetic energy barrier. The question is: can such phenomena be observed in nanomagnets with odd number of magnetic ions? The answer is not directly obvious because cyclic chains with odd-numbered coupled spins are frustrated as one cannot obtain a perfect Néel order. These frustrated spins can indeed be observed experimentally, so they are of interest. In this Letter, we theoretically investigate macroscopic quantum tunneling in these odd spin systems with arbitrary spins s, in the presence of a magnetic field applied along the plane of the magnet. In contrast to systems with an even-numbered coupled spins, the ground state of the cyclic odd-spin system contains a topological soliton due to spin frustration. Thus the classical ground state is 2N-fold degenerate as the soliton can be placed anywhere along the ring with total Sz = ±s. Small quantum fluctuations delocalize the soliton with a formation of an energy band. We obtain this energy band using degenerate perturbation theory at order 2s. We show that the soliton ground state is chiral for half-odd integer spins and non-chiral for integer spins. From the structure of the energy band we infer that as the value of the spin increases the inelastic polarized neutron-scattering intensity may increase or decrease depending on the strengths of the parameters of the Hamiltonian.
Spin-polarized reflection of electrons in a two-dimensional electron system
Bulletin of the American Physical Society, 2003
We present a method to create spin-polarized beams of ballistic electrons in a two-dimensional electron system in the presence of spin-orbit interaction. Scattering of a spin-unpolarized injected beam from a lithographic barrier leads to the creation of two fully spin-polarized side beams, in addition to an unpolarized specularly reflected beam. Experimental magnetotransport data on InSb/InAlSb heterostructures demonstrate the spin-polarized reflection in a mesoscopic geometry, and confirm our theoretical predictions. PACS: 72.25.Dc ; 73.23.Ad ; 73.63.Hs *Corresponding author: Department of Physics and Astronomy, Clippinger Laboratories, Ohio University, Athens OH 45701 (heremans@ohiou.edu) Hong Chen et al. Page 1 of 14 9/12/2003 The spin of electrons and holes in semiconductor heterostructures has attracted much interest, as a factor to realize new spin-based electronic device concepts [1], and for its potential in realizing quantum computational schemes [2]. In heterostructures, s...
Spin Textures in Strongly Coupled Electron Spin and Magnetic or Nuclear Spin Systems in Quantum Dots
Physical Review Letters, 2012
Controlling electron spins strongly coupled to magnetic and nuclear spins in solid state systems is an important challenege in the field of spintronics and quantum computation. We show here that electron droplets with no net spin in semiconductor quantum dots strongly coupled with magnetic ion/nuclear spin systems break down at low temperature and form a non-trivial antiferromagnetic spatially ordered spin-texture of magneto-polarons. The spatially ordered combined electron-magnetic ion spin-texture, associated with spontaneous symmetry-breaking in the parity of electronic charge density and magnetization of magnetic ions, emerge from both ab-initio density functional approach to the electronic system coupled with mean-field approximation for the magnetic/nuclear spin system and fully mircoscopic exact diagonalization of small systems. The predicted phase diagram determines the critical temperature as a function of coupling strength and identifies possible phases of the strongly coupled spin system. This prediction may arrest fluctuations in spin system and open the way to control, manipulate and prepare magnetic and nuclear spin ensembles in semiconductor nanostructures.
Spin-resolved inelastic electron scattering by spin waves in noncollinear magnets
Physical Review B
Topological noncollinear magnetic phases of matter are at the heart of many proposals for future information nanotechnology, with novel device concepts based on ultrathin films and nanowires. Their operation requires understanding and control of the underlying dynamics, including excitations such as spin waves. So far, no experimental technique has attempted to probe large wave-vector spin waves in noncollinear low-dimensional systems. In this paper, we explain how inelastic electron scattering, being suitable for investigations of surfaces and thin films, can detect the collective spin-excitation spectra of noncollinear magnets. To reveal the particularities of spin waves in such noncollinear samples, we propose the usage of spin-polarized electron-energy-loss spectroscopy augmented with a spin analyzer. With the spin analyzer detecting the polarization of the scattered electrons, four spin-dependent scattering channels are defined, which allow us to filter and select specific spin-wave modes. We take as examples a topological nontrivial skyrmion lattice, a spin-spiral phase, and the conventional ferromagnet. Then we demonstrate that, counterintuitively and in contrast to the ferromagnetic case, even non-spin-flip processes can generate spin waves in noncollinear substrates. The measured dispersion and lifetime of the excitation modes permit us to fingerprint the magnetic nature of the substrate.
Quenching of the 2D Metallic State by Aligning the Electron Spins
Australian Journal of Physics
We discuss the destabilisation of the electron 2D metallic state by an in-plane magnetic field. We demonstrate that such a field can destabilise the metallic state through spin polarisation which significantly enhances the exchange correlations between electrons. We find that the conducting phase of the fully spin polarised system is almost completely suppressed. We discuss this phenomenon within a memory function formalism which treats both disorder and exchange-correlation effects. We determine the shift in the position of the metal–insulator phase boundary as the system is polarised by an increasing parallel magnetic field.
Theory of Tunneling Spectroscopy in Ferromagnetic Nanoparticles
Physical Review Letters, 2000
We present a theory of the low-energy excitations of a ferromagnetic metal nanoparticle. In addition to the particle-hole excitations, which occur in a paramagnetic metal nanoparticle, we predict a branch of excitations involving the magnetization-orientation collective coordinate. Tunneling matrix elements are in general sizable for several different collective states associated with the same band configuration. We point out that the average change in ground state spin per added electron differs from non-interacting quasiparticle expectations, and that the change in the spin-polarization, due to Zeeman coupling, is strongly influenced by Coulomb blockade physics.