Browsing by Subject "Spintronics"

Now showing 1 - 4 of 4

Open Access
A controllable spin prism
(IOP Institute of Physics Publishing, 2009) Hakiolu, T.
Based on Khodas et al (2004 Phys. Rev. Lett. 92 086602), we propose a device acting like a controllable prism for an incident spin. The device is a large quantum well where Rashba and Dresselhaus spin-orbit interactions are present and controlled by the plunger gate potential, the electric field and the barrier height. A totally destructive interference can be manipulated externally between the Rashba and Dresselhaus couplings. The spin-dependent transmission/reflection amplitudes are calculated as the control parameters are changed. The device operates as a spin prism/converter/filter in different regimes and may stimulate research in promising directions in spintronics in analogy with linear optics. © 2009 IOP Publishing Ltd.
Open Access
Magnetic ground state in FeTe2,VS2, and NiTe2 monolayers: antiparallel magnetic moments at chalcogen atoms
(American Physical Society, 2020) Aras, M.; Kılıç, Ç.; Çıracı, Salim
Our analysis based on the results of hybrid and semilocal density-functional calculations with and without Hubbard U correction for on-site Coulomb interactions reveals the true magnetic ground states of three transition-metal dichalcogenide monolayers, viz., FeTe2,VS2, and NiTe2, which comprise inhomogeneous magnetic moment configurations. In contrast to earlier studies considering only the magnetic moments of transition-metal atoms, the chalcogen atoms by themselves have significant, antiparallel magnetic moments owing to the spin polarization through p−d hybridization. The latter is found to be true for both H and T phases of FeTe2,VS2, and NiTe2 monolayers. Our predictions show that the FeTe2 monolayer in its lowest-energy structure is a half metal, which prevails under both compressive and tensile strains. Half metallicity occurs also in the FeTe2 bilayer but disappears in thicker multilayers. The VS2 monolayer is a magnetic semiconductor; it has two different band gaps of different character and widths for different spin polarization. The NiTe2 monolayer, which used to be known as a nonmagnetic metal, is indeed a magnetic metal with a small magnetic moment. These monolayers with intriguing electronic and magnetic properties can attain new functionalities for spintronic applications.
Open Access
Magnetization of silicene via coverage with gadolinium: effects of thickness, symmetry, strain, and coverage
(American Physical Society, 2021-12-14) Demirci, S.; Gorkan, T.; Çallioğlu, Şafak; Yüksel, Y.; Akıncı, Ü.; Aktürk, E.; Çıracı, Salim
When covered by gadolinium (Gd) atoms, silicene, a freestanding monolayer of Si atoms in a honeycomb network, remains stable above the room temperature and becomes a two-dimensional (2D) ferromagnetic semiconductor, despite the antiferromagnetic ground state of three-dimensional bulk GdSi2 crystal. In thin GdSi2 multilayers, even if magnetic moments are ordered parallel in the same Gd atomic planes, they are antiparallel between nearest Gd planes; hence they exhibit a ferrimagnetic behavior. In contrast, a freestanding Gd2Si2 monolayer constructed by covering silicene from both sides by Gd atoms is a stable antiferromagnetic metal due to the mirror symmetry. While multilayers covered by Gd from both sides having an odd number of Gd planes have a ferrimagneticlike ground state, even-numbered ones have antiferromagnetic ground state, but none of them is ferromagnetic. Silicon atoms intervening between Gd planes are responsible for these intriguing magnetic orders conforming with the recent experiments performed on Si(111) surface. Additionally, the magnetic states of these 2D gadolinium disilicide monolayers can be monitored by applied tensile strain and by the coverage/decoration of Gd. These predictions obtained by using first-principles, spin-polarized, density functional theory calculations combined with Monte Carlo simulations herald that C, B, Si, Ge, Sn, and their compounds functionalized by rare-earth atoms can lead to novel nanostructures in 2D spintronics.
Open Access
Spintronic properties of zigzag-edged triangular graphene flakes
(AIP Publishing LLC, 2010) Şahin, H.; Senger, R. T.; Çıracı, Salim
We investigate quantum transport properties of triangular graphene flakes with zigzag edges by using first principles calculations. Triangular graphene flakes have large magnetic moments which vary with the number of hydrogen atoms terminating its edge atoms and scale with its size. Electronic transmission and current-voltage characteristics of these flakes, when contacted with metallic electrodes, reveal spin valve and remarkable rectification features. The transition from ferromagnetic to antiferromagnetic state under bias voltage can, however, terminate the spin polarizing effects for specific flakes. Geometry and size dependent transport properties of graphene flakes may be crucial for spintronic nanodevice applications.