Emergence of high spin polarization of conductance in atomic-size Co-Au contacts

Sivkov, Ilia; Brovko, Oleg O.; Бажанов, Д. И.; Stepanyuk, V. S.

doi:10.1103/physrevb.89.075436

Cited by 13 publications

(7 citation statements)

References 38 publications

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“…Attempts to scale down the basic memory unit by using atomic and molecular nanocontacts with high magnetoresistance, that is,"spin valve" behaviour, are being pursued. Generally, only modest values of magnetoresistance are obtained in metallic nanocontacts, 20,71,73 although a larger value of 73% has been calculated for a Au chain between Co electrodes, 156 a configuration which also realizes a relatively highly spin-polarized conductance due to the blocking of the minority spin channels by strong s-d z 2 hybridisation at the Co/Au interface. Larger values of magnetoresistance have been calculated and observed for molecular nanocontacts, 79,[157][158][159][160][161] reaching (ideally) infinite magnetoresistance for certain non-magnetic π-conjugated molecules between ferromagnetic leads.…”

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confidence: 99%

Metallic, magnetic and molecular nanocontacts

et al. 2016

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Scanning tunnelling microscopy and break-junction experiments realize metallic and molecular nanocontacts that act as ideal one-dimensional channels between macroscopic electrodes. Emergent nanoscale phenomena typical of these systems encompass structural, mechanical, electronic, transport, and magnetic properties. This Review focuses on the theoretical explanation of some of these properties obtained with the help of first-principles methods. By tracing parallel theoretical and experimental developments from the discovery of nanowire formation and conductance quantization in gold nanowires to recent observations of emergent magnetism and Kondo correlations, we exemplify the main concepts and ingredients needed to bring together ab initio calculations and physical observations. It can be anticipated that diode, sensor, spin-valve and spin-filter functionalities relevant for spintronics and molecular electronics applications will benefit from the physical understanding thus obtained.

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Section: And References Therein)mentioning

confidence: 99%

Metallic, magnetic and molecular nanocontacts

et al. 2016

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“…Absent in bulk and surface systems, their presence is generally attributed to electron confinement in the nano-contact's chain bound by two electrodes leading to the appearance of standing waves and localized electronic states. 43,44 Another way of describing the origin of the peaks (as is discussed in our previous work 45 ) is by considering the chain as a molecular entity, in which case the peaks around the Fermi level can be seen as antibonding states of the chain living in the localizing chain poten-tial and complementary to the bonding states lying some 1 eV lower in energy (see the wide-range PDOS plots in Fig. S2).…”

Section: Resultsmentioning

confidence: 99%

Gate control of spin-polarized conductance in alloyed transitional metal nanocontacts

et al. 2017

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To date, endeavors in nanoscale spintronics are dominated by the use of single-electron or singlespin transistors having at their heart a semiconductor, metallic or molecular quantum dot who's localized states are non-spin-degenerate and can be controlled by an external bias applied via a gate electrode. Adjusting the bias of the gate one can realign those states with respect to the chemical potentials of the leads and thus tailor the spin-polarized transmission properties of the device. Here we show that similar functionality can be achieved in a purely metallic junction comprised of a metallic magnetic chains attached to metallic paramagnetic leads and biased by a gate electrode. Our ab initio calculations of electron transport through mixed Pt-Fe (Fe-Pd and Fe-Rh) atomic chains suspended between Pt (Pd and Rh) electrodes show that spin-polarized confined states of the chain can be shifted by the gate bias causing a change in the relative contributions of majority and minority channels to the nano-contact's conductance. As a result, we observe strong dependence of conductance spin-polarization on the applied gate potential. In some cases the spin-polarization of conductance can even be reversed in sign upon gate potential application, which is a remarkable and promising trait for spintronic applications. INTRODUCTIONAs spintronics evolves from a holy grail of science and technology into an everyday phenomenon, its foundations demand for the same cornerstones as conventional spindegenerate electronics is built on: miniaturization, robustness and tunability. Technological progress nowadays has enabled both scientists and engineers to build nanometer and sub-nanometer-scale devices not only with elaborate and volatile break junction, 1-4 electromigration 5 or STM extraction 6 techniques, but also with virtually integration-ready nanotube/nanowire and lithography based technologies.7-12 Robustness of transport properties is usually achieved by a combination of single-electron and coulomb-blockade physics 7,13-16 with strong magnetic properties guaranteed by the use of magnetic materials with high spin moment 7,17 and geometry/topology based stability of the latter.18-20 The tunability, or the susceptibility of spin-dependent transport properties 21,22 to external perturbations can be achieved in several ways. Orientation and ordering of spins in magnetic systems can be "programmed" into atomic-scale junctions at construction stage (e.g., by tuning the chemical composition and geometry of the device 4,7,[17][18][19][23][24][25] ), but it is even more important and challenging to be able to dynamically and reversibly tune those properties after the junction has been completed or integrated into a circuit. The "traditional" way of controlling transmission properties of both conventional and single-electron transistors is the field effect, i.e. external bias application by means of an additional gate electrode. Gate bias in a three-terminal device can be used to control both paramagnetic transport 2,26,27 and magnetic...

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“…Here, we investigate point contacts with ferromagnetic Co electrodes. Diverging values for the spin-polarisation of Co have been reported in the range between 10% and nearly 50% in the bulk, while in atomic contacts a higher spinpolarisation of 50%-70% has been measured recently [31]. The normal metal part of the junction is made of Pd, a strongly paramagnetic metal close to the Stoner criterion for ferromagnetism.…”

Section: Methodsmentioning

confidence: 92%

Microwave-induced direct spin-flip transitions in mesoscopic Pd/Co heterojunctions

et al. 2016

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We experimentally investigate the effect of resonant microwave absorption on the magneto-conductance of tunable Co/Pd point contacts. At the interface a non-equilibrium spin accumulation is created via microwave absorption and can be probed via point contact spectroscopy. We interpret the results as a signature of direct spin-flip excitations in Zeeman-split spin-subbands within the Pd normal metal part of the junction. The inverse effect, which is associated with the emission of a microwave photon in a ferromagnet/normal metal point contact, can also be detected via its unique signature in transport spectroscopy.

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Emergence of high spin polarization of conductance in atomic-size Co-Au contacts

Cited by 13 publications

References 38 publications

Metallic, magnetic and molecular nanocontacts

Metallic, magnetic and molecular nanocontacts

Gate control of spin-polarized conductance in alloyed transitional metal nanocontacts

Microwave-induced direct spin-flip transitions in mesoscopic Pd/Co heterojunctions

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