Spin-polarized tunneling

Moodera, Jagadeesh S.; Meservey, R.

doi:10.1016/b978-012088487-2/50004-2

Cited by 14 publications

(14 citation statements)

References 191 publications

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“…4(a) shows the energy diagram for Co 2+ ion in a tetrahedral site. In this context, the absorptions observed at 567, 612 and 658 nm is attributed to the transitions 4 A 2 (F) / 2 A 1 (G), 4 A 2 (F) / 4 T 1 (P) and 4 A 2 (F) / 2 E(G). 40 Therefore, the observation of these transitions for our doped thin lms is an indication that the Co ions in ZnO matrix have a +2 oxidation state and are located in a tetrahedral site.…”

Section: Methodsmentioning

confidence: 89%

“…The observed spectra were very similar to those found in literature, 38 with the ZnO absorption edge in the range of 380 nm and absorption bands at 567, 612 and 658 nm associated with Co 2+ ions at the 3d 7 tetrahedral coordination, with the 4 F state corresponding to the lowest energy state, as well as the 4 P, 2 G, 2 P, 2 H and 2 D states corresponding to the excited states. 39 Once in a tetrahedral site, the 4 F state splits into 4 A 2 ( 4 F), 4 T 2 ( 4 F) and 4 T 1 ( 4 F) due to the crystalline eld, here, 4 A 2 ( 4 F) state became the fundamental one. Likewise, the 2 G state splits into 2 A 1 ( 2 G), 2 E( 2 G), 2 T 1 ( 2 G) and 2 T 2 ( 2 G).…”

Section: Methodsmentioning

confidence: 98%

“…The development of novel spintronic materials and spin-based electronic devices is a hot topic of current research in materials science and condensed matter physics. 1,2 Although a few spintronic devices based on ferromagnetic/non-magnetic heterostructures have been successfully realized, [3][4][5][6] the addition of ferromagnetic properties to semiconductors has been revealed to be one of the most challenging task. Ferromagnetic semiconductors are interesting from the technological point of view, mainly due to the possibility of integration of spintronics in the conventional semiconductor technologies and to the introduction of new functionalities, like the control of magnetic properties through the manipulation of the density of free charge carriers and electric elds.…”

Section: Introductionmentioning

confidence: 99%

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Preparation and structural-optical characterization of dip-coated nanostructured Co-doped ZnO dilute magnetic oxide thin films

et al. 2017

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Section: Methodsmentioning

confidence: 89%

Section: Methodsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Preparation and structural-optical characterization of dip-coated nanostructured Co-doped ZnO dilute magnetic oxide thin films

et al. 2017

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“…Since the bulk DOS of TIs is not polarized in spin, the Zeeman splitting caused by the 3 kOe field might not be enough to observe any significant effect. Whereas the absence of the surface driven spin polarization in the TI response may indicate a loss of spin polarization through spin scattering at the interfaces or defects, [37][38][39] the ZBA seen in the conductance vs bias may relate to loss of spin information due to Co atoms inside the Al 2 O 3 barrier which acts as scattering centers or to higher surface defect densities of the TI, as shown by XRD.…”

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confidence: 99%

Band structure of topological insulators from noise measurements in tunnel junctions

Cascales

Martínez

Katmis

et al. 2015

Applied Physics Letters

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The unique properties of spin-polarized surface or edge states in topological insulators (TIs) make these quantum coherent systems interesting from the point of view of both fundamental physics and their implementation in low power spintronic devices. Here we present such a study in TIs, through tunneling and noise spectroscopy utilizing TI/Al 2 O 3 /Co tunnel junctions with bottom TI electrodes of either Bi 2 Te 3 or Bi 2 Se 3 . We demonstrate that features related to the band structure of the TI materials show up in the tunneling conductance and even more clearly through low frequency noise measurements. The bias dependence of 1/f noise reveals peaks at specific energies corresponding to band structure features of the TI. TI tunnel junctions could thus simplify the study of the properties of such quantum coherent systems that can further lead to the manipulation of their spin-polarized properties for technological purposes. A topological insulator (TI) is a material which is insulating in the bulk but presents spin-dependent conducting edge or surface states which are protected by time-reversal symmetry.1-3 A 2D or 3D TI presents edge or surface states, respectively, which are spin-polarized in-plane, and locked at right angles to the carrier momentum, so that electrons with spin-up/down propagate in opposite directions. The edge or surface states of a TI consist of an odd number of massless Dirac cones. These properties along with their high mobility make TI materials interesting for next generation, low dissipation, and spintronic applications 4,5 in which the electron spins are manipulated even without any magnetic fields. The experimental surge regarding these materials occurred with the prediction of Bi-based TIs 6 and their posterior experimental realization.7 Bi 2 Se 3 and Bi 2 Te 3 , in particular, became the prototypical TI materials that were studied most heavily.To date, the experimental verification of the band structure of TI materials has been predominantly carried out by angle-resolved photoemission spectroscopy (ARPES), which yields energy-momentum graphs of band dispersion for probing depths of under a few nm. 7,8 Also, the use of spin-ARPES has allowed the determination of the spin dependence of the topological surface states. 9 On the other hand, the use of scanning tunneling microscope (STM) allows obtaining information regarding the local density of states (DOS) and the topography of surfaces. By the study of quasiparticle scattering with STM, bands can be mapped very close to the Fermi surface, with a considerably lower energy range and at a smaller scale than with ARPES. [10][11][12][13] Although immensely useful, these techniques are usually cumbersome and the conditions of study are far from a practical application of TIs. A versatile and relatively simple technique to determine the DOS of TI materials could be the study of electronic transport and noise through planar tunneling devices. So far, individual or heterostructure devices with TI layers have mainly dealt with lateral electro...

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“…The half-metallicity is induced by the formation of a bandgap only in one of the electron-spin bands. There have been five types of half-metallic ferromagnets theoretically proposed and experimentally demonstrated to date: (i) oxide compounds (e.g., rutile CrO 2 [26] and spinel Fe 3 O 4 [27]); (ii) perovskites (e.g., (La,Sr)MnO 3 [28]); and, (iii) magnetic semiconductors, including Zinc-blende compounds (e.g., EuO and EuS [29], (Ga,Mn)As [30] and CrAs [31]) and (iv) Heusler alloys (e.g., NiMnSb [32]). Magnetic semiconductors have been reported to show 100% spin polarisation due to their Zeeman splitting in two spin bands.…”

Section: Heusler-alloy Junctionsmentioning

confidence: 99%

Perpendicular Magnetic Anisotropy in Heusler Alloy Films and Their Magnetoresistive Junctions

et al. 2018

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For the sustainable development of spintronic devices, a half-metallic ferromagnetic film needs to be developed as a spin source with exhibiting 100% spin polarisation at its Fermi level at room temperature. One of the most promising candidates for such a film is a Heusler-alloy film, which has already been proven to achieve the half-metallicity in the bulk region of the film. The Heusler alloys have predominantly cubic crystalline structures with small magnetocrystalline anisotropy. In order to use these alloys in perpendicularly magnetised devices, which are advantageous over in-plane devices due to their scalability, lattice distortion is required by introducing atomic substitution and interfacial lattice mismatch. In this review, recent development in perpendicularly-magnetised Heusler-alloy films is overviewed and their magnetoresistive junctions are discussed. Especially, focus is given to binary Heusler alloys by replacing the second element in the ternary Heusler alloys with the third one, e.g., MnGa and MnGe, and to interfacially-induced anisotropy by attaching oxides and metals with different lattice constants to the Heusler alloys. These alloys can improve the performance of spintronic devices with higher recording capacity.

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Spin-polarized tunneling

Cited by 14 publications

References 191 publications

Preparation and structural-optical characterization of dip-coated nanostructured Co-doped ZnO dilute magnetic oxide thin films

Preparation and structural-optical characterization of dip-coated nanostructured Co-doped ZnO dilute magnetic oxide thin films

Band structure of topological insulators from noise measurements in tunnel junctions

Perpendicular Magnetic Anisotropy in Heusler Alloy Films and Their Magnetoresistive Junctions

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