The phenomena of spin-filter tunnelling

Moodera, Jagadeesh S.; Santos, Tiffany S.; Nagahama, Taro

doi:10.1088/0953-8984/19/16/165202

Cited by 249 publications

(242 citation statements)

References 80 publications

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“…Clearly, if the barrier height is different for the different spin species, then the current polarizations will increase exponentially with the insulating layer thickness, leading to full spin polarization for thick barriers. 3,12 Devices constructed with this principle are called spin-filter tunnel junctions (SFTJs). The quest for manufacturing SFTJs then reduces to that of finding suitable ferromagnetic semiconductors.…”

Section: T (E) ∝ Exp[−2κ( E)t] With κ( E) = √mentioning

confidence: 99%

“…An energy gap of 1.0 eV separates the half-filled majority Eu-4f band from the Eu-5d conduction band. 3 SFTJs based on polycrystalline EuO in the form of a metal/EuO/metal heterojunction have been studied in several recent experiments. [16][17][18][19][20][21][22] However, the spin transport properties of crystalline epitaxial EuO junctions have not been studied theoretically so far.…”

Section: T (E) ∝ Exp[−2κ( E)t] With κ( E) = √mentioning

confidence: 99%

“…Second, the TMR consistently decreases with increasing the applied voltage and/or the temperature, and so the operation of a practical device utilizing a magnetic tunnel junction is limited to low bias. 3 The high TMR 4,5 found in Fe/MgO-based junctions is caused by the symmetry filtering provided by the MgO barrier, together with the particular spin polarization of the Fe electrodes. Only electrons with 1 symmetry and with small transverse momentum contribute significantly to the current [6][7][8][9][10][11][12] through MgO, and in Fe these are found only in the majority spins for electrons at the Fermi energy, so that the Fe/MgO stack acts like a spin filter in the current flow.…”

Section: Introductionmentioning

confidence: 99%

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Electronic transport through EuO spin-filter tunnel junctions

et al. 2012

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Epitaxial spin-filter tunnel junctions based on the ferromagnetic semiconductor europium monoxide (EuO) are investigated by means of density functional theory. In particular, we focus on the spin transport properties of Cu(100)/EuO(100)/Cu(100) junctions. The dependence of the transmission coefficient and the current-voltage curves on the interface spacing and EuO thickness is explained in terms of the EuO density of states and the complex band structure. Furthermore, we also discuss the relation between the spin transport properties and the Cu-EuO interface geometry. The level alignment of the junction is sensitively affected by the interface spacing, since this determines the charge transfer between EuO and the Cu electrodes. Our calculations indicate that EuO epitaxially grown on Cu can act as a perfect spin filter, with a spin polarization of the current close to 100%, and with both the Eu-5d conduction-band and the Eu-4f valence-band states contributing to the coherent transport. For epitaxial EuO on Cu, a symmetry filtering is observed, with the 1 states dominating the transmission. This leads to a transport gap larger than the fundamental EuO band gap. Importantly, the high spin polarization of the current is preserved up to large bias voltages.

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Section: T (E) ∝ Exp[−2κ( E)t] With κ( E) = √mentioning

confidence: 99%

Section: T (E) ∝ Exp[−2κ( E)t] With κ( E) = √mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electronic transport through EuO spin-filter tunnel junctions

et al. 2012

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“…1a and Methods), that has no net spin. When these molecules are grown on a ferromagnetic surface, interface spin transfer causes a hybridized organometallic supramolecular magnetic layer to develop, which shows a large magnetic anisotropy and spin-filter properties 21 . This interface layer creates a spin-dependent resistance and gives rise to an interface magnetoresistance (IMR) effect.…”

mentioning

confidence: 99%

“…4b), defining two different barrier heights for spin tunnelling injection: a lower one for spin-down electrons (φ ↓ ) of 0.73 eV and a higher one for spin-up electrons (φ ↑ ) of 0.87 eV, leading to a spin-dependent interface resistance. It is well known that conventional spin-filter tunnelling of this type (using magnetic semiconductors such as EuS, EuO, and so on) can be highly efficient 21 .…”

mentioning

confidence: 99%

Interface-engineered templates for molecular spin memory devices

Raman

Kamerbeek

Mukherjee

et al. 2013

Nature

413

409

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The use of molecular spin state as a quantum of information for storage, sensing and computing has generated considerable interest in the context of next-generation data storage and communication devices 1, 2 , opening avenues for developing multifunctional molecular spintronics 3 . Such ideas have been researched extensively, using singlemolecule magnets 4, 5 and molecules with a metal ion 6 or nitrogen vacancy 7 as localized spin-carrying centres for storage and for realizing logic operations 8 . However, the electronic coupling between the spin centres of these molecules is rather weak, which makes construction of quantum memory registers a challenging task 9 . In this regard, delocalized carbon-based radical species with unpaired spin, such as phenalenyl 10 , have shown promise. These phenalenyl moieties, which can be regarded as graphene fragments, are formed by the fusion of three benzene rings and belong to the class of open-shell systems. The spin structure of these molecules responds to external stimuli 11, 12 (such as light, and electric and magnetic fields), which provides novel schemes for performing spin memory and logic operations. Here we construct a molecular device using such molecules as templates to engineer interfacial spin transfer resulting from hybridization and magnetic exchange interaction with the surface of a ferromagnet; the device shows an unexpected interfacial magnetoresistance of more than 20 per cent near room temperature. Moreover, we successfully demonstrate the formation of a nanoscale magnetic molecule with a well-defined magnetic hysteresis on ferromagnetic surfaces. Owing to strong magnetic coupling with the ferromagnet, such independent switching of an adsorbed magnetic molecule has been unsuccessful with single-molecule magnets 13 . Our findings suggest the use of chemically amenable phenalenyl-based molecules as a viable and scalable platform for building molecular-scale quantum spin memory and processors for technological development.The diversity and flexibility of molecular synthesis has given researchers ample freedom to design functional molecules for spintronics. These include molecular magnets 14 , spinfilter molecules 15 , spin-crossover molecules 16 , molecular batteries 17 , molecular conductors 10 , molecular switches 12 , and spacer layers for organic spin valves 18 and magnetic tunnel junctions 19,20 . Using such synthetic techniques, we have designed a neutral planar phenalenyl-based molecule, zinc methyl phenalenyl (ZMP, C 14 H 10 O 2 Zn; see Fig. 1a and Methods), that has no net spin. When these molecules are grown on a ferromagnetic surface, interface spin transfer causes a hybridized organometallic supramolecular magnetic layer to develop, which shows a large magnetic anisotropy and spin-filter properties 21 . This interface layer creates a spin-dependent resistance and gives rise to an interface magnetoresistance (IMR) effect.

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